Stage-Specific IgA/IgG Plasma Cell Signatures Characterize Ulcerative Colitis Disease Progression

Stage-Specific IgA/IgG Plasma Cell Signatures Characterize Ulcerative Colitis Disease Progression | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Stage-Specific IgA/IgG Plasma Cell Signatures Characterize Ulcerative Colitis Disease Progression Chuyu Xie, Xiangyun Li, Tingzhen Zhang, Dingzhun Liao, Changfei Qin This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9397376/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract Background Plasma cell infiltration is characteristic of ulcerative colitis (UC), yet immunoglobulin subtype-specific alterations across disease stages remain poorly defined. This study aimed to characterize quantitative and distributional patterns of IgA- and IgG-positive plasma cells in UC rectal mucosa across disease stages. Methods Rectal biopsies from healthy controls ( n = 6) and UC patients at different stages—active inflammation ( n = 6), chronic quiescent ( n = 6), and post-treatment remission with 5-aminosalicylic acid (5-ASA) ( n = 6)—were retrospectively collected between June 2024 and June 2025. H&E staining and immunohistochemical (IHC) analysis for IgA- and IgG-positive cells were assessed. A dextran sulfate sodium (DSS)-induced murine colitis model with 5-ASA therapy was established for experimental validation. Results Active UC demonstrated fragmented, sparse superficial IgA distribution with significantly reduced IHC scores compared to healthy controls (continuous banding pattern), while IgG showed diffuse transmural infiltration with elevated scores. Chronic quiescent UC exhibited patchy, discontinuous superficial IgA with partially recovered scores, alongside persistent transmural IgG with decreased scores. Post-treatment remission restored continuous IgA banding with further increased scores. In the murine model, IgA+ plasma cells decreased dose-dependently, while IgG+ cells increased. 5-ASA treatment significantly reversed these alterations. Conclusions Stage-specific quantitative and distributional patterns of IgA- and IgG-positive cells constitute distinctive immunopathological signatures of UC. These signatures may serve as histopathological biomarkers for objective disease staging. ulcerative colitis immunoglobulin A immunoglobulin G plasma cells histopathological biomarker disease staging 5-ASA Figures Figure 1 Figure 2 Figure 3 Introduction Ulcerative colitis (UC) is a chronic inflammatory bowel disease (IBD) characterized by continuous mucosal inflammation extending proximally from the rectum to variable lengths of the colon [ 1 ]. The disease course typically follows a relapsing-remitting pattern, encompassing active inflammatory phases, chronic quiescent periods, and post-treatment remission states [ 2 ]. Accurate assessment of these disease stages requires reliable biomarkers that reflect underlying mucosal pathology. Current evaluation of UC activity integrates clinical indices (such as the Mayo score), endoscopic findings, and histopathological assessment. Among these, histological evaluation provides direct evidence of mucosal inflammation and healing [ 3 , 4 ]. In active UC, microscopic examination can reveal distorted glandular structures and the infiltration of plasma cells, eosinophils, and neutrophils in colon tissue. However, conventional histological interpretation suffers from considerable inter-observer variability, limiting reproducibility and standardization [ 5 ]. The development of objective, quantifiable histopathological biomarkers is therefore essential to improve disease staging precision and monitor therapeutic responses. The intestinal mucosa harbors the body's largest population of antibody-producing plasma cells, with immunoglobulin A (IgA) representing the predominant isotype under physiological conditions [ 6 ]. IgA-producing plasma cells are concentrated within the lamina propria, where they maintain mucosal homeostasis through immune exclusion of pathogens, regulation of commensal microbiota, and contribution to immune tolerance [ 7 ]. Recent single-cell sequencing studies have revealed that in inflamed colon tissues of UC patients, the proportion of IgA-positive cells is significantly lower, whereas the proportion of immunoglobulin G (IgG)-positive cells is greater [ 8 , 9 ]. However, comprehensive characterization of the dynamic changes in both IgA- and IgG-positive cells across the complete spectrum of UC stages remains incomplete. The rectum is affected primarily in the vast majority of UC cases, serving as the ideal site for disease monitoring through endoscopic biopsy [ 10 ]. This study aims to define the quantitative and distributional pattern characteristics of IgA- and IgG-positive plasma cells in human UC rectal mucosa at different disease stages and validate these findings in an experimental colitis model with therapeutic intervention. Materials and Methods Human Tissue Specimens Rectal mucosal biopsies from healthy controls (n = 6) and UC patients with or without medical therapy (5-aminosalicylic acid, 5-ASA) were retrospectively collected between June 2024 and June 2025. Healthy control biopsies were obtained from individuals undergoing colonoscopy for screening or mild functional symptoms with normal endoscopic and histological findings. Clinicopathological data for UC patients were collected and are presented in Supplementary Table 1. The diagnosis of UC was established by integrating clinical symptoms, endoscopic findings, and microscopic examination. The study was approved by the Institutional Review Board at the Seventh Affiliated Hospital of Sun Yat-sen University (application ID: KY-2025-168-01). Histological and Immunohistochemical Analysis Tissue sections were stained with hematoxylin and eosin (H&E) for routine histological evaluation. Active UC was identified by cryptitis or crypt abscesses (neutrophil infiltration within crypt epithelium or aggregation in crypt lumens); chronic UC was identified by dense plasma cell infiltration without cryptitis or crypt abscesses. Immunohistochemical (IHC) staining was conducted via the two-step Envision method. The primary antibodies used included IgA (ZSGB-BIO, 432F8H3, China) and IgG (ZSGB-BIO, ZA0448, China). The scoring system for IgA integrated cell density (1: 0–5 cells/HPF (0.34 mm²); 2: 6–10 cells/0.34 mm²; 3: 11–20 cells/0.34 mm²; 4: >20 cells/0.34 mm²) and distribution pattern (1: discontinuous/scattered; 2: discontinuous/patchy superficial; 3: continuous superficial band). The scoring system for IgG integrated cell density (1: 0–5 cells/0.34 mm²; 2: 6–10 cells/0.34 mm²; 3: 11–20 cells/0.34 mm²; 4: >20 cells/0.34 mm²) and distribution pattern (1: scattered sparse distribution; 2: patchy aggregation at mucosal base; 3: sheet-like infiltration throughout mucosal layers). For cell density scoring, 10 high-power fields (HPFs) in hotspot areas were counted and the mean value was calculated. IHC scoring was performed independently by two pathologists blinded to clinical data. The final IHC score was calculated as the sum of density and distribution components. Dextran sulfate sodium (DSS) -Induced Murine Colitis Model with 5-ASA Treatment C57BL/6 mice (8–10 weeks old, male) were randomized into four groups ( n = 6 per group): (1) Water control; (2) 3% DSS (MW 36,000–50,000, MP Biomedicals) in drinking water for 7 days; (3) 5% DSS for 7 days; (4) 5% DSS for 7 days with concurrent 5-ASA (100 mg/kg/day) administered by oral gavage. Mice were euthanized on day 7, and rectum tissues were harvested for histological analysis and flow cytometry. The histological score ranges from 0–12 and is based on four main pathological features previously described [ 11 ]: (1) damage (0, none; 1, mild/superficial; 2, moderate/involving the muscularis mucosae; 3, severe/transmural); (2) inflammation (0, none; 1, mild; 2, moderate; 3, severe); (3) extent (0, none; 1, focal; 2, limited to one segment; 3, involving more than one segment); and (4) regeneration (0, complete re-epithelialization; 1, broad multifocal re-epithelialization; 2, focal re-epithelialization; 3, none). Flow Cytometry Lamina propria mononuclear cells were isolated as previously described [ 12 ]. Cells were stained with fluorochrome-conjugated antibodies: CD45 (PC7, Tonbo Biosciences), CD19 (APC, BioLegend), IgA (FITC, eBioscience™), and IgG (PC5.5, BioLegend). The gating strategy involved sequential selection of lymphocytes based on forward and side scatter, single cells, live cells, CD45 + leukocytes, CD19 + B cells, and finally IgA + or IgG+ plasma cells (Supplementary Fig. 1 for detailed gating strategy). Samples were analyzed on a FACS Canto flow cytometer (BD Biosciences™). Flow cytometry data analysis was conducted using FlowJo version 10. Statistical Analysis Data are presented as mean ± SD. Comparisons among multiple groups were performed using one-way ANOVA followed by Tukey's post-hoc test for multiple comparisons. Normality was assessed using Shapiro-Wilk test. Homogeneity of variances was confirmed by Levene's test. P -values < 0.05 were considered statistically significant (* P < 0.05, ** P < 0.01, *** P < 0.001, **** P < 0.0001; ns, not significant). Statistical analyses were performed using GraphPad Prism 9.0. Results Representative Histopathological Features of UC Rectal Mucosa Across Disease Stages As shown in Fig. 1 , H&E staining reveals characteristic histological changes at each disease stage (A, D, G, J), while immunohistochemical staining for IgA and IgG demonstrates stage-specific differences (B-C, E-F, H-I, K-L). In healthy rectal mucosa, regularly arranged crypts with minimal lamina propria inflammatory infiltration were observed (Fig. 1 A). In active UC, marked crypt architectural distortion with reduced crypt numbers, extensive lymphoplasmacytic lamina propria infiltration, and prominent neutrophilic cryptitis were observed (Fig. 1 D). Chronic UC demonstrated relatively preserved crypt numbers with dense plasma cell infiltration concentrated at the mucosal base and between crypts (Fig. 1 G). Post-treatment remission specimens exhibited regenerative crypt epithelial hyperplasia with relatively regular arrangement, reduced intercrypt inflammatory infiltrates, though occasional basal lymphoid aggregates persisted (Fig. 1 J). Stage-Specific Alterations of IgA- and IgG-Positive Cells in Ulcerative Colitis In healthy rectal mucosa, IHC staining revealed that the majority of these plasma cells were positive for IgA and exhibited a continuous band-like distribution pattern (Fig. 1 B). In contrast, there were only a small number of scattered IgG-positive cells in the lamina propria (Fig. 1 C). In active UC, IgA immunostaining revealed fragmented, discontinuous distribution restricted to superficial mucosal layers, with complete loss of continuous banding architecture (Fig. 1 E). Quantitative analysis confirmed significantly reduced IgA IHC scores compared to healthy controls (Fig. 2 A). In contrast, IgG-positive cells exhibited marked expansion with dense, diffuse infiltration extending throughout the entire mucosal thickness from superficial to basal layers (Fig. 1 F), accompanied by significantly elevated IgG IHC scores (Fig. 2 B). In chronic UC, IgA-positive cells demonstrated patchy, discontinuous superficial distribution (Fig. 1 H), with elevated IHC scores compared to active disease (Fig. 2 A). Meanwhile, IgG-positive cells persisted with transmural distribution pattern (Fig. 1 I), though IgG IHC scores decreased significantly compared to active disease (Fig. 2 B). In post-treatment remission specimens, IgA-positive plasma cells showed restoration of continuous, band-like superficial distribution closely resembling the healthy pattern (Fig. 1 K), with further elevated IgA IHC scores compared to chronic UC (Fig. 2 A). However, IgG-positive cells maintained scanty distribution throughout mucosal layers with focal basal layer aggregation (Fig. 1 L), and IgG IHC scores significantly lower than chronic UC (Fig. 2 B). Validation in DSS-Induced Murine Colitis: Disease Severity and Therapeutic Response To validate these findings experimentally and assess therapeutic reversibility, we established a DSS-induced acute colitis model with 5-ASA intervention. H&E staining confirmed dose-dependent histological damage: 3% DSS induced moderate colitis, while 5% DSS caused severe mucosal damage characterized by epithelial ulceration, necrosis, and dense inflammatory infiltrates (Fig. 3 A). 5-ASA treatment significantly ameliorated histological damage in 5% DSS mice (Fig. 3 A, B). Flow cytometric analysis showed that the proportion of CD45 + cells significantly increased in the 5% DSS-induced group but decreased after 5-ASA treatment (Supplementary Fig. 2A). In contrast, CD19 + B cell proportions remained stable across all groups (Supplementary Fig. 2B). However, within the CD19 + compartment, the proportion of IgA+ cells decreased with increasing DSS concentration, whereas IgG+ cells increased. Importantly, 5-ASA treatment significantly reversed these alterations, restoring IgA+ cells and reducing IgG+ cells (Fig. 3 C-F). These results confirm that the IgA/IgG imbalance correlates with histological acute colitis severity and is reversible with effective therapy. Discussion This study establishes characteristic, stage-specific signatures of IgA-and IgG-positive plasma cells in rectal mucosa that objectively distinguish different phases of UC. Our findings reveal four distinct immunophenotypic patterns: (1) Healthy mucosa maintains immune tolerance through continuous superficial IgA banding with minimal IgG; (2) Active disease demonstrates IgA fragmentation with diffuse IgG infiltration; (3) Chronic quiescent disease shows transitional IgA recovery with persistent distribution abnormalities and elevated IgG; and (4) Post-treatment remission restores continuous IgA patterning with reduced but persistent IgG elevation. These patterns, validated in the DSS-induced acute colitis model, indicate distinctive immunopathological signatures of UC and provide quantifiable histopathological biomarkers suitable for disease classification. The continuous superficial IgA band in healthy rectal mucosa represents the physiological "frontline" defense maintaining host-microbial mutualism [ 13 ]. This organized architecture facilitates secretory IgA transcytosis to the luminal surface, where it mediates immune exclusion of pathogens and regulates commensal bacterial colonization. Conversely, diffuse transmural IgG distribution suggests extensive immune complex formation and complement activation, potentially perpetuating tissue damage [ 14 ]. The reduction in IgA+ plasma cells may reflect impaired class-switch recombination to IgA, with concomitant expansion of IgG-skewed plasmablasts in active UC. The complete disruption of this pattern in active UC—with IgA reduction, fragmentation, and diffuse IgG replacement—aligns with established concepts of mucosal barrier dysfunction and aberrant adaptive immune activation in UC pathogenesis [ 13 , 15 ]. Our finding that chronic UC retains discontinuous IgA distribution indicates persistent subclinical barrier impairment, despite elevated IHC scores for IgA and decreased IHC scores for IgG compared to active disease. This histological feature may explain why patients in clinical remission frequently experience early relapse and supports the concept of "histological remission" as a more stringent treatment target than clinical or endoscopic remission alone [ 16 ]. The post-treatment remission pattern is particularly instructive. While continuous IgA banding is substantially restored with elevated IgA IHC scores compared to chronic UC—indicating re-establishment of mucosal immune tolerance—the persistent IgG elevation and basal layer aggregation suggest residual immune memory or low-grade chronic activation. This dissociation between IgA restoration and IgG persistence may identify patients at risk for future relapse despite apparent clinical healing, warranting longitudinal follow-up studies to validate this hypothesis [ 17 ]. The murine model validation is crucial for several reasons. First, the dose-dependent IgA/IgG alterations confirm these patterns reflect inflammation severity rather than disease-specific artifacts. Second, the 5-ASA reversal demonstrates that immunoglobulin patterns are dynamic and responsive to therapy, supporting their utility as pharmacodynamic biomarkers. From a translational perspective, these characteristic patterns offer objective, categorical descriptors suitable for AI image analysis [ 18 ]. The distinct IgA distribution states—continuous band, patchy discontinuous, fragmented absent—provide clear visual criteria that may reduce inter-observer variability in histopathological assessment. Integration of quantitative IgA/IgG scores with artificial intelligence algorithms could enable automated, standardized classification of UC disease stages, supporting precision medicine approaches [ 19 ]. There are several limitations to this study. Firstly, this proof-of-concept study requires validation in an independent, large-scale cohort to establish biomarker efficacy. Secondly, we did not assess correlations with clinical outcomes or microbiome composition, which may modulate immunoglobulin responses. Future longitudinal studies should track plasma cell dynamics, correlate immunophenotypes with relapse rates, and explore mechanistic pathways driving class-switch recombination. Additionally, while the DSS model recapitulates acute inflammation, it does not fully reflect the chronic relapsing nature of UC [ 20 ]. Future studies should employ chronic colitis models (e.g., DSS cycles) to validate stage-specific signatures. Conclusions This study defines characteristic quantitative and distributional signatures of IgA- and IgG-positive plasma cells across the spectrum of UC disease stages in rectal mucosa. These objective histopathological biomarkers provide a framework for new disease classification and offer insights into mucosal immune mechanisms underlying UC pathogenesis, therapeutic response, and potentially, relapse prediction. Declarations Author Contributions QCF: conception and design of the study, statistical analysis and data interpretation. XCY and LXY: data interpretation, revision of the article, and final approval. LDZ and ZTZ: responsible for H&E staining and IHC staining. Funding Declaration None Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Ethics approval and consent to participate The study was conducted in accordance with the Declaration of Helsinki and was approved by the Institutional Review Board (IRB) of the Seventh Affiliated Hospital of Sun Yat-sen University. The requirement for informed consent was waived due to the retrospective nature by the IRB of the Seventh Affiliated Hospital (application ID: KY-2025-168-01). Consent for publication Not applicable. Data availability The datasets used during the present study are available from the corresponding author upon reasonable request. Acknowledgments During the preparation of this work, the authors used GPT-4 model to assist with English translation and language refinement. After using this tool, the authors carefully reviewed, edited, and approved the final content. The authors take full responsibility for the integrity and accuracy of the published article. References Ungaro R, Mehandru S, Allen PB, Peyrin-Biroulet L, Colombel JF. Ulcerative colitis. Lancet (London England). 2017;389(10080):1756–70. Rubin DT, Ananthakrishnan AN, Siegel CA, Barnes EL, Long MD. ACG Clinical Guideline Update: Ulcerative Colitis in Adults. Am J Gastroenterol. 2025;120(6):1187–224. 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Supplementary Files SupplementaryFigureandTable1.docx Cite Share Download PDF Status: Under Review Version 1 posted Reviewers invited by journal 19 Apr, 2026 Editor invited by journal 17 Apr, 2026 Editor assigned by journal 16 Apr, 2026 Submission checks completed at journal 16 Apr, 2026 First submitted to journal 12 Apr, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9397376","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":627115257,"identity":"fa341499-9a44-46e8-8ded-eb5ab8607a55","order_by":0,"name":"Chuyu Xie","email":"","orcid":"","institution":"The Seventh Affiliated Hospital of Sun Yat-sen University","correspondingAuthor":false,"prefix":"","firstName":"Chuyu","middleName":"","lastName":"Xie","suffix":""},{"id":627115258,"identity":"4e18e2c8-249d-4907-8a80-e30026f32396","order_by":1,"name":"Xiangyun Li","email":"","orcid":"","institution":"The Seventh Affiliated Hospital of Sun Yat-sen University","correspondingAuthor":false,"prefix":"","firstName":"Xiangyun","middleName":"","lastName":"Li","suffix":""},{"id":627115260,"identity":"812221a2-242a-46f2-9392-92608a28578f","order_by":2,"name":"Tingzhen Zhang","email":"","orcid":"","institution":"Seventh Affiliated Hospital of Sun Yat-sen University","correspondingAuthor":false,"prefix":"","firstName":"Tingzhen","middleName":"","lastName":"Zhang","suffix":""},{"id":627115261,"identity":"a1149c5f-2abc-464e-be36-7c27370f2805","order_by":3,"name":"Dingzhun Liao","email":"","orcid":"","institution":"Seventh Affiliated Hospital of Sun Yat-sen University","correspondingAuthor":false,"prefix":"","firstName":"Dingzhun","middleName":"","lastName":"Liao","suffix":""},{"id":627115266,"identity":"56ae968f-9145-41d3-af86-3dc8aeb12bba","order_by":4,"name":"Changfei Qin","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABAUlEQVRIiWNgGAWjYDACZhCyqZFjYGBsPAATlCCsJe2YMVBLA5FawLrSmBMbgAzitPAd5z34uSCBLX1t+2GgLX8O2xscYD54m4fBLg+XFsnDfMnSMxJkcredSWw4wNh2OHHDAbZkax6G5GJcWgwO85gx8/5gy912AKSl4XCCwQEeM2kehgNgp+LUwpPAnG52/iHMYfzfiNKSYHYDaAsD22HGDQd42PBqkTzMYyzNk3DMcNsNoC2JbemJMw+zGVvOMUjGqYXv/BnDzzwJNfJm59MfPvjwx9qe73jzwxtvKuxwakHEBQgkMDSDIxfoYFzq0bUwMNThUToKRsEoGAUjFQAA23VaGGHAoQoAAAAASUVORK5CYII=","orcid":"","institution":"Seventh Affiliated Hospital of Sun Yat-sen University","correspondingAuthor":true,"prefix":"","firstName":"Changfei","middleName":"","lastName":"Qin","suffix":""}],"badges":[],"createdAt":"2026-04-13 01:08:17","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9397376/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9397376/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":108007289,"identity":"5168ae4a-790a-420b-8313-3228540a2fca","added_by":"auto","created_at":"2026-04-28 12:59:22","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1168241,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eRepresentative histopathological and immunohistochemical staining of IgA- and IgG-positive plasma cells across UC disease stages. \u003c/strong\u003e(A-C) Healthy control showing regular crypt architecture with continuous superficial IgA+ cells banding and minimal IgG+ cells. (D-F) Active UC demonstrating marked crypt architectural distortion and prominent neutrophilic cryptitis, fragmented superficial IgA+ cells, and diffuse transmural IgG+ cells infiltration. (G-I) Chronic UC demonstrated relatively preserved crypt numbers with dense plasma cell infiltration, patchy discontinuous IgA+ cells and persistent transmural IgG+ cells. (J-L) Post-treatment remission with restored continuous IgA+ cells banding and reduced IgG+ cells. Scale bars: 200 μm (main images), 50 μm (insets).\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-9397376/v1/ad18b95d135e8d62dca49278.png"},{"id":107916978,"identity":"0249c6de-6624-449f-a41e-794b32514e71","added_by":"auto","created_at":"2026-04-27 14:21:02","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":147437,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eQuantitative analysis of IgA and IgG IHC scores across disease stages. \u003c/strong\u003e(A) IgA IHC scores showing significant reduction in active UC, elevated scores in chronic UC and post-treatment remission. (B) IgG IHC scores demonstrating elevation in active UC, and reduced scores in chronic UC and post-treatment remission. \u003cem\u003en\u003c/em\u003e = 6 per group. Data presented as mean ± SD. *\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05, **\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.01, ***\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.001, ****\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.0001 by one-way ANOVA with Tukey's post-hoc test\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-9397376/v1/f63dddcdaa9039a8c9c072ca.png"},{"id":108006625,"identity":"4be60c90-9e32-46d3-995b-9e2c6e3c6a5b","added_by":"auto","created_at":"2026-04-28 12:56:11","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":744630,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eExperimental validation in DSS-induced murine colitis. \u003c/strong\u003e(A) Representative H\u0026amp;E staining showing dose-dependent histological damage and 5-ASA-mediated therapeutic effects. (B) Quantitative histological scores. (C-D) Flow cytometric analysis and quantification of IgA+ plasma cells (gated on CD19+). (E-F) Flow cytometric analysis and quantification of IgG+ plasma cells. \u003cem\u003en\u003c/em\u003e = 6 per group. Data presented as mean ± SD. *\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05, **\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.01, ***\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.001, ****\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.0001 by one-way ANOVA with Tukey's post-hoc test.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-9397376/v1/2997d9ac63b9d6afef31dd54.png"},{"id":108008730,"identity":"7de3bc47-de4a-4341-9f73-0d546d9a70a3","added_by":"auto","created_at":"2026-04-28 13:08:13","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2254432,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9397376/v1/affffe77-f0f2-4ef5-ad04-0527bcd252a0.pdf"},{"id":107916977,"identity":"6b5c0677-85ab-48d1-99d2-036489eb3139","added_by":"auto","created_at":"2026-04-27 14:21:02","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":157616,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryFigureandTable1.docx","url":"https://assets-eu.researchsquare.com/files/rs-9397376/v1/e0fdb676c7fafc79cd615e6e.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Stage-Specific IgA/IgG Plasma Cell Signatures Characterize Ulcerative Colitis Disease Progression","fulltext":[{"header":"Introduction","content":"\u003cp\u003eUlcerative colitis (UC) is a chronic inflammatory bowel disease (IBD) characterized by continuous mucosal inflammation extending proximally from the rectum to variable lengths of the colon [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The disease course typically follows a relapsing-remitting pattern, encompassing active inflammatory phases, chronic quiescent periods, and post-treatment remission states [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Accurate assessment of these disease stages requires reliable biomarkers that reflect underlying mucosal pathology.\u003c/p\u003e \u003cp\u003eCurrent evaluation of UC activity integrates clinical indices (such as the Mayo score), endoscopic findings, and histopathological assessment. Among these, histological evaluation provides direct evidence of mucosal inflammation and healing [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. In active UC, microscopic examination can reveal distorted glandular structures and the infiltration of plasma cells, eosinophils, and neutrophils in colon tissue. However, conventional histological interpretation suffers from considerable inter-observer variability, limiting reproducibility and standardization [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. The development of objective, quantifiable histopathological biomarkers is therefore essential to improve disease staging precision and monitor therapeutic responses.\u003c/p\u003e \u003cp\u003eThe intestinal mucosa harbors the body's largest population of antibody-producing plasma cells, with immunoglobulin A (IgA) representing the predominant isotype under physiological conditions [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. IgA-producing plasma cells are concentrated within the lamina propria, where they maintain mucosal homeostasis through immune exclusion of pathogens, regulation of commensal microbiota, and contribution to immune tolerance [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Recent single-cell sequencing studies have revealed that in inflamed colon tissues of UC patients, the proportion of IgA-positive cells is significantly lower, whereas the proportion of immunoglobulin G (IgG)-positive cells is greater [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. However, comprehensive characterization of the dynamic changes in both IgA- and IgG-positive cells across the complete spectrum of UC stages remains incomplete.\u003c/p\u003e \u003cp\u003eThe rectum is affected primarily in the vast majority of UC cases, serving as the ideal site for disease monitoring through endoscopic biopsy [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. This study aims to define the quantitative and distributional pattern characteristics of IgA- and IgG-positive plasma cells in human UC rectal mucosa at different disease stages and validate these findings in an experimental colitis model with therapeutic intervention.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eHuman Tissue Specimens\u003c/h2\u003e \u003cp\u003eRectal mucosal biopsies from healthy controls (n\u0026thinsp;=\u0026thinsp;6) and UC patients with or without medical therapy (5-aminosalicylic acid, 5-ASA) were retrospectively collected between June 2024 and June 2025. Healthy control biopsies were obtained from individuals undergoing colonoscopy for screening or mild functional symptoms with normal endoscopic and histological findings. Clinicopathological data for UC patients were collected and are presented in Supplementary Table\u0026nbsp;1. The diagnosis of UC was established by integrating clinical symptoms, endoscopic findings, and microscopic examination. The study was approved by the Institutional Review Board at the Seventh Affiliated Hospital of Sun Yat-sen University (application ID: KY-2025-168-01).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eHistological and Immunohistochemical Analysis\u003c/h3\u003e\n\u003cp\u003eTissue sections were stained with hematoxylin and eosin (H\u0026amp;E) for routine histological evaluation. Active UC was identified by cryptitis or crypt abscesses (neutrophil infiltration within crypt epithelium or aggregation in crypt lumens); chronic UC was identified by dense plasma cell infiltration without cryptitis or crypt abscesses.\u003c/p\u003e \u003cp\u003eImmunohistochemical (IHC) staining was conducted via the two-step Envision method. The primary antibodies used included IgA (ZSGB-BIO, 432F8H3, China) and IgG (ZSGB-BIO, ZA0448, China). The scoring system for IgA integrated cell density (1: 0\u0026ndash;5 cells/HPF (0.34 mm\u0026sup2;); 2: 6\u0026ndash;10 cells/0.34 mm\u0026sup2;; 3: 11\u0026ndash;20 cells/0.34 mm\u0026sup2;; 4: \u0026gt;20 cells/0.34 mm\u0026sup2;) and distribution pattern (1: discontinuous/scattered; 2: discontinuous/patchy superficial; 3: continuous superficial band). The scoring system for IgG integrated cell density (1: 0\u0026ndash;5 cells/0.34 mm\u0026sup2;; 2: 6\u0026ndash;10 cells/0.34 mm\u0026sup2;; 3: 11\u0026ndash;20 cells/0.34 mm\u0026sup2;; 4: \u0026gt;20 cells/0.34 mm\u0026sup2;) and distribution pattern (1: scattered sparse distribution; 2: patchy aggregation at mucosal base; 3: sheet-like infiltration throughout mucosal layers). For cell density scoring, 10 high-power fields (HPFs) in hotspot areas were counted and the mean value was calculated. IHC scoring was performed independently by two pathologists blinded to clinical data. The final IHC score was calculated as the sum of density and distribution components.\u003c/p\u003e\n\u003ch3\u003eDextran sulfate sodium (DSS) -Induced Murine Colitis Model with 5-ASA Treatment\u003c/h3\u003e\n\u003cp\u003e \u003cem\u003eC57BL/6\u003c/em\u003e mice (8\u0026ndash;10 weeks old, male) were randomized into four groups (\u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;6 per group): (1) Water control; (2) 3% DSS (MW 36,000\u0026ndash;50,000, MP Biomedicals) in drinking water for 7 days; (3) 5% DSS for 7 days; (4) 5% DSS for 7 days with concurrent 5-ASA (100 mg/kg/day) administered by oral gavage. Mice were euthanized on day 7, and rectum tissues were harvested for histological analysis and flow cytometry.\u003c/p\u003e \u003cp\u003eThe histological score ranges from 0\u0026ndash;12 and is based on four main pathological features previously described [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]: (1) damage (0, none; 1, mild/superficial; 2, moderate/involving the muscularis mucosae; 3, severe/transmural); (2) inflammation (0, none; 1, mild; 2, moderate; 3, severe); (3) extent (0, none; 1, focal; 2, limited to one segment; 3, involving more than one segment); and (4) regeneration (0, complete re-epithelialization; 1, broad multifocal re-epithelialization; 2, focal re-epithelialization; 3, none).\u003c/p\u003e\n\u003ch3\u003eFlow Cytometry\u003c/h3\u003e\n\u003cp\u003eLamina propria mononuclear cells were isolated as previously described [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Cells were stained with fluorochrome-conjugated antibodies: CD45 (PC7, Tonbo Biosciences), CD19 (APC, BioLegend), IgA (FITC, eBioscience\u0026trade;), and IgG (PC5.5, BioLegend). The gating strategy involved sequential selection of lymphocytes based on forward and side scatter, single cells, live cells, CD45\u0026thinsp;+\u0026thinsp;leukocytes, CD19\u0026thinsp;+\u0026thinsp;B cells, and finally IgA\u0026thinsp;+\u0026thinsp;or IgG+ plasma cells (Supplementary Fig.\u0026nbsp;1 for detailed gating strategy). Samples were analyzed on a FACS Canto flow cytometer (BD Biosciences\u0026trade;). Flow cytometry data analysis was conducted using FlowJo version 10.\u003c/p\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eData are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD. Comparisons among multiple groups were performed using one-way ANOVA followed by Tukey's post-hoc test for multiple comparisons. Normality was assessed using Shapiro-Wilk test. Homogeneity of variances was confirmed by Levene's test. \u003cem\u003eP\u003c/em\u003e-values\u0026thinsp;\u0026lt;\u0026thinsp;0.05 were considered statistically significant (*\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05, **\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01, ***\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001, ****\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.0001; ns, not significant). Statistical analyses were performed using GraphPad Prism 9.0.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eRepresentative Histopathological Features of UC Rectal Mucosa Across Disease Stages\u003c/h2\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e, H\u0026amp;E staining reveals characteristic histological changes at each disease stage (A, D, G, J), while immunohistochemical staining for IgA and IgG demonstrates stage-specific differences (B-C, E-F, H-I, K-L). In healthy rectal mucosa, regularly arranged crypts with minimal lamina propria inflammatory infiltration were observed (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eA). In active UC, marked crypt architectural distortion with reduced crypt numbers, extensive lymphoplasmacytic lamina propria infiltration, and prominent neutrophilic cryptitis were observed (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eD). Chronic UC demonstrated relatively preserved crypt numbers with dense plasma cell infiltration concentrated at the mucosal base and between crypts (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eG). Post-treatment remission specimens exhibited regenerative crypt epithelial hyperplasia with relatively regular arrangement, reduced intercrypt inflammatory infiltrates, though occasional basal lymphoid aggregates persisted (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eJ).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eStage-Specific Alterations of IgA- and IgG-Positive Cells in Ulcerative Colitis\u003c/h3\u003e\n\u003cp\u003eIn healthy rectal mucosa, IHC staining revealed that the majority of these plasma cells were positive for IgA and exhibited a continuous band-like distribution pattern (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eB). In contrast, there were only a small number of scattered IgG-positive cells in the lamina propria (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eC).\u003c/p\u003e \u003cp\u003eIn active UC, IgA immunostaining revealed fragmented, discontinuous distribution restricted to superficial mucosal layers, with complete loss of continuous banding architecture (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eE). Quantitative analysis confirmed significantly reduced IgA IHC scores compared to healthy controls (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eA). In contrast, IgG-positive cells exhibited marked expansion with dense, diffuse infiltration extending throughout the entire mucosal thickness from superficial to basal layers (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eF), accompanied by significantly elevated IgG IHC scores (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eB).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn chronic UC, IgA-positive cells demonstrated patchy, discontinuous superficial distribution (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eH), with elevated IHC scores compared to active disease (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eA). Meanwhile, IgG-positive cells persisted with transmural distribution pattern (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eI), though IgG IHC scores decreased significantly compared to active disease (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eB).\u003c/p\u003e \u003cp\u003eIn post-treatment remission specimens, IgA-positive plasma cells showed restoration of continuous, band-like superficial distribution closely resembling the healthy pattern (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eK), with further elevated IgA IHC scores compared to chronic UC (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eA). However, IgG-positive cells maintained scanty distribution throughout mucosal layers with focal basal layer aggregation (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eL), and IgG IHC scores significantly lower than chronic UC (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eB).\u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eValidation in DSS-Induced Murine Colitis: Disease Severity and Therapeutic Response\u003c/h2\u003e \u003cp\u003eTo validate these findings experimentally and assess therapeutic reversibility, we established a DSS-induced acute colitis model with 5-ASA intervention. H\u0026amp;E staining confirmed dose-dependent histological damage: 3% DSS induced moderate colitis, while 5% DSS caused severe mucosal damage characterized by epithelial ulceration, necrosis, and dense inflammatory infiltrates (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eA). 5-ASA treatment significantly ameliorated histological damage in 5% DSS mice (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eA, B).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFlow cytometric analysis showed that the proportion of CD45 + cells significantly increased in the 5% DSS-induced group but decreased after 5-ASA treatment (Supplementary Fig.\u0026nbsp;2A). In contrast, CD19 + B cell proportions remained stable across all groups (Supplementary Fig.\u0026nbsp;2B). However, within the CD19 + compartment, the proportion of IgA+ cells decreased with increasing DSS concentration, whereas IgG+ cells increased. Importantly, 5-ASA treatment significantly reversed these alterations, restoring IgA+ cells and reducing IgG+ cells (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eC-F). These results confirm that the IgA/IgG imbalance correlates with histological acute colitis severity and is reversible with effective therapy.\u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study establishes characteristic, stage-specific signatures of IgA-and IgG-positive plasma cells in rectal mucosa that objectively distinguish different phases of UC. Our findings reveal four distinct immunophenotypic patterns: (1) Healthy mucosa maintains immune tolerance through continuous superficial IgA banding with minimal IgG; (2) Active disease demonstrates IgA fragmentation with diffuse IgG infiltration; (3) Chronic quiescent disease shows transitional IgA recovery with persistent distribution abnormalities and elevated IgG; and (4) Post-treatment remission restores continuous IgA patterning with reduced but persistent IgG elevation. These patterns, validated in the DSS-induced acute colitis model, indicate distinctive immunopathological signatures of UC and provide quantifiable histopathological biomarkers suitable for disease classification.\u003c/p\u003e\u003cp\u003eThe continuous superficial IgA band in healthy rectal mucosa represents the physiological \"frontline\" defense maintaining host-microbial mutualism [\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e]. This organized architecture facilitates secretory IgA transcytosis to the luminal surface, where it mediates immune exclusion of pathogens and regulates commensal bacterial colonization. Conversely, diffuse transmural IgG distribution suggests extensive immune complex formation and complement activation, potentially perpetuating tissue damage [\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e]. The reduction in IgA+ plasma cells may reflect impaired class-switch recombination to IgA, with concomitant expansion of IgG-skewed plasmablasts in active UC. The complete disruption of this pattern in active UC—with IgA reduction, fragmentation, and diffuse IgG replacement—aligns with established concepts of mucosal barrier dysfunction and aberrant adaptive immune activation in UC pathogenesis [\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eOur finding that chronic UC retains discontinuous IgA distribution indicates persistent subclinical barrier impairment, despite elevated IHC scores for IgA and decreased IHC scores for IgG compared to active disease. This histological feature may explain why patients in clinical remission frequently experience early relapse and supports the concept of \"histological remission\" as a more stringent treatment target than clinical or endoscopic remission alone [\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe post-treatment remission pattern is particularly instructive. While continuous IgA banding is substantially restored with elevated IgA IHC scores compared to chronic UC—indicating re-establishment of mucosal immune tolerance—the persistent IgG elevation and basal layer aggregation suggest residual immune memory or low-grade chronic activation. This dissociation between IgA restoration and IgG persistence may identify patients at risk for future relapse despite apparent clinical healing, warranting longitudinal follow-up studies to validate this hypothesis [\u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe murine model validation is crucial for several reasons. First, the dose-dependent IgA/IgG alterations confirm these patterns reflect inflammation severity rather than disease-specific artifacts. Second, the 5-ASA reversal demonstrates that immunoglobulin patterns are dynamic and responsive to therapy, supporting their utility as pharmacodynamic biomarkers.\u003c/p\u003e\u003cp\u003eFrom a translational perspective, these characteristic patterns offer objective, categorical descriptors suitable for AI image analysis [\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e]. The distinct IgA distribution states—continuous band, patchy discontinuous, fragmented absent—provide clear visual criteria that may reduce inter-observer variability in histopathological assessment. Integration of quantitative IgA/IgG scores with artificial intelligence algorithms could enable automated, standardized classification of UC disease stages, supporting precision medicine approaches [\u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThere are several limitations to this study. Firstly, this proof-of-concept study requires validation in an independent, large-scale cohort to establish biomarker efficacy. Secondly, we did not assess correlations with clinical outcomes or microbiome composition, which may modulate immunoglobulin responses. Future longitudinal studies should track plasma cell dynamics, correlate immunophenotypes with relapse rates, and explore mechanistic pathways driving class-switch recombination. Additionally, while the DSS model recapitulates acute inflammation, it does not fully reflect the chronic relapsing nature of UC [\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e]. Future studies should employ chronic colitis models (e.g., DSS cycles) to validate stage-specific signatures.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThis study defines characteristic quantitative and distributional signatures of IgA- and IgG-positive plasma cells across the spectrum of UC disease stages in rectal mucosa. These objective histopathological biomarkers provide a framework for new disease classification and offer insights into mucosal immune mechanisms underlying UC pathogenesis, therapeutic response, and potentially, relapse prediction.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eQCF:\u0026nbsp;conception and design of the study, statistical analysis and data interpretation. XCY and LXY: data interpretation, revision of the article, and final approval. LDZ and ZTZ: responsible for H\u0026amp;E staining and IHC staining.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding Declaration\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was conducted in accordance with the Declaration of Helsinki and was approved by the Institutional Review Board (IRB) of the Seventh Affiliated Hospital of Sun Yat-sen University. The requirement for informed consent was waived due to the retrospective nature by the IRB of the Seventh Affiliated Hospital (application ID: KY-2025-168-01).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used during the present study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDuring the preparation of this work, the authors used GPT-4 model to assist with English translation and language refinement. After using this tool, the authors carefully reviewed, edited, and approved the final content. The authors take full responsibility for the integrity and accuracy of the published article.\u0026nbsp;\u003c/p\u003e\n"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eUngaro R, Mehandru S, Allen PB, Peyrin-Biroulet L, Colombel JF. Ulcerative colitis. Lancet (London England). 2017;389(10080):1756\u0026ndash;70.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRubin DT, Ananthakrishnan AN, Siegel CA, Barnes EL, Long MD. ACG Clinical Guideline Update: Ulcerative Colitis in Adults. Am J Gastroenterol. 2025;120(6):1187\u0026ndash;224.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eScarallo L, Fioretti L, Paci M, Naldini S, Renzo S, Barp J, Gissi A, Di Paola M, Villanacci V, Lionetti P. Histological healing as a predictor of sustained clinical remission in paediatric ulcerative colitis. 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Int J Mol Sci 2020, 21(23).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePabst O, Izcue A. Secretory IgA: controlling the gut microbiota. Nat reviews Gastroenterol Hepatol. 2022;19(3):149\u0026ndash;50.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUzzan M, Martin JC, Mesin L, Livanos AE, Castro-Dopico T, Huang R, Petralia F, Magri G, Kumar S, Zhao Q, et al. Ulcerative colitis is characterized by a plasmablast-skewed humoral response associated with disease activity. Nat Med. 2022;28(4):766\u0026ndash;79.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMitsialis V, Wall S, Liu P, Ordovas-Montanes J, Parmet T, Vukovic M, Spencer D, Field M, McCourt C, Toothaker J, et al. Single-Cell Analyses of Colon and Blood Reveal Distinct Immune Cell Signatures of Ulcerative Colitis and Crohn's Disease. 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Identification and exploration of pharmacological pyroptosis-related biomarkers of ulcerative colitis. Front Immunol. 2022;13:998470.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIacucci M, Santacroce G, Zammarchi I, Maeda Y, Del Amor R, Meseguer P, Kolawole BB, Chaudhari U, Di Sabatino A, Danese S, et al. Artificial intelligence and endo-histo-omics: new dimensions of precision endoscopy and histology in inflammatory bowel disease. lancet Gastroenterol Hepatol. 2024;9(8):758\u0026ndash;72.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eStidham RW, Takenaka K. Artificial Intelligence for Disease Assessment in Inflammatory Bowel Disease: How Will it Change Our Practice? \u003cem\u003eGastroenterology\u003c/em\u003e 2022, 162(5):1493\u0026ndash;506.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhu J, Yang F, Sang L, Zhai J, Zhang X, Yue D, Li S, Li Y, Lu C, Sun X. IL-33 Aggravates DSS-Induced Acute Colitis in Mouse Colon Lamina Propria by Enhancing Th2 Cell Responses. \u003cem\u003eMediators of inflammation\u003c/em\u003e 2015, 2015:913041.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-gastroenterology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmge","sideBox":"Learn more about [BMC Gastroenterology](http://bmcgastroenterol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bmge/default.aspx","title":"BMC Gastroenterology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"ulcerative colitis, immunoglobulin A, immunoglobulin G, plasma cells, histopathological biomarker, disease staging, 5-ASA","lastPublishedDoi":"10.21203/rs.3.rs-9397376/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9397376/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003ePlasma cell infiltration is characteristic of ulcerative colitis (UC), yet immunoglobulin subtype-specific alterations across disease stages remain poorly defined. This study aimed to characterize quantitative and distributional patterns of IgA- and IgG-positive plasma cells in UC rectal mucosa across disease stages.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eRectal biopsies from healthy controls (\u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;6) and UC patients at different stages\u0026mdash;active inflammation (\u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;6), chronic quiescent (\u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;6), and post-treatment remission with 5-aminosalicylic acid (5-ASA) (\u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;6)\u0026mdash;were retrospectively collected between June 2024 and June 2025. H\u0026amp;E staining and immunohistochemical (IHC) analysis for IgA- and IgG-positive cells were assessed. A dextran sulfate sodium (DSS)-induced murine colitis model with 5-ASA therapy was established for experimental validation.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eActive UC demonstrated fragmented, sparse superficial IgA distribution with significantly reduced IHC scores compared to healthy controls (continuous banding pattern), while IgG showed diffuse transmural infiltration with elevated scores. Chronic quiescent UC exhibited patchy, discontinuous superficial IgA with partially recovered scores, alongside persistent transmural IgG with decreased scores. Post-treatment remission restored continuous IgA banding with further increased scores. In the murine model, IgA+ plasma cells decreased dose-dependently, while IgG+ cells increased. 5-ASA treatment significantly reversed these alterations.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eStage-specific quantitative and distributional patterns of IgA- and IgG-positive cells constitute distinctive immunopathological signatures of UC. These signatures may serve as histopathological biomarkers for objective disease staging.\u003c/p\u003e","manuscriptTitle":"Stage-Specific IgA/IgG Plasma Cell Signatures Characterize Ulcerative Colitis Disease Progression","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-27 14:20:58","doi":"10.21203/rs.3.rs-9397376/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewersInvited","content":"","date":"2026-04-19T13:41:12+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-04-17T08:31:17+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-04-17T02:44:58+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-04-17T02:44:43+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Gastroenterology","date":"2026-04-13T00:57:38+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-gastroenterology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmge","sideBox":"Learn more about [BMC Gastroenterology](http://bmcgastroenterol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bmge/default.aspx","title":"BMC Gastroenterology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"d8ee0d82-1927-4f8a-8acc-df8072a0a16d","owner":[],"postedDate":"April 27th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-04-27T14:20:58+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-27 14:20:58","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9397376","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9397376","identity":"rs-9397376","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}