Dissecting the causal effects of interleukin receptor-related factors and the risk of developing endometriosis: a two-sample Mendelian randomization study

This study investigates the causal associations between interleukin receptor-related factors and the development of endometriosis, as their etiology and pathophysiology remain largely unknown. A two-sample Mendelian randomization (MR) approach was employed to analyze genetic variants associated with interleukin receptor related factors as instrumental variables (IVs). The F-values have to be > 10 to exclude weak instrumental bias. The primary analysis was conducted using the inverse variance weighted (IVW) method, with confirmation using the MR-Egger, weighted median (WM), simple mode, and weighted mode methods. Sensitivity analyses were performed to ensure robustness, including tests for heterogeneity, pleiotropy, and leave-one-out. Multivariable MR (MVMR) analysis was used to assess the direct and mediated effects of immune cells. The results indicated significant causal associations between interleukin receptor factors prot-a-1542 (IL-6Rβ), prot-a-1530 (IL-3Rα), and prot-b-38 (IL-1RL1) and endometriosis. Reverse MR analysis showed that endometriosis did not significantly affect prot-a-1530 or prot-b-38. After adjusting for confounders like body mass index and smoking, these factors retained their significance. Additionally, immune cells(ebi-a-GCST90001951) were found to mediate the relationship between prot-b-38 and endometriosis, with an indirect effect accounting for approximately 6.38% of the total effect. This study provides new insights into endometriosis mechanisms involving specific interleukin receptor factors.

Endometriosis is a gynecological disorder featuring the presence and growth of endometrial tissue located outside the uterus. It is a common condition affecting, at a different severity, approximately 5%-10% of females of reproductive age globally [Citation1,Citation2]. Endometriosis is associated with significant morbidity, including infertility, pelvic pain, and decreased quality of life, and places an important pressure on healthcare systems [Citation3]. Despite its high prevalence, the underlying causes of endometriosis and its mechanisms remain unknown but are probably multifactorial [Citation4]. Because of the unknown pathogenesis, the current treatments are nonspecific and limited to alleviating the symptoms. They include hormonal therapies suppressing the menstrual cycle to prevent endometrial growth and surgical interventions such as diagnostic laparoscopy to remove the visible lesions and total hysterectomy with salpingo-ovariectomy [Citation5]. Hormonal treatments and diagnostic laparoscopy often provide only temporary relief, and there is a high risk of recurrence after discontinuation of hormonal treatment or after laparoscopy [Citation4]. Hysterectomy with salpingo-ovariectomy is kept for patients with poorly managed symptoms using other modalities and without a desire for preserving fertility [Citation6–8]. Despite the lack of a comprehensive understanding of the pathophysiology of endometriosis, recent research has shown that inflammation is a crucial factor in developing endometriosis [Citation9], and inflammation is involved in pain and subfertility [Citation7]. In particular, cytokines such as interleukins have been implicated in promoting the survival and proliferation of ectopic endometrial cells [Citation10,Citation11]. Interleukin receptors and their signaling pathways have emerged as potential therapeutic targets due to their involvement in immune responses within the pelvic microenvironment [Citation9,Citation12]. Although the available data show associations between interleukin receptor-related factors and endometriosis [Citation9–12], confounding factors and risk of reverse causality are inherent to observational association studies, preventing the determination of causal relationships [Citation13,Citation14]. Unfortunately, longitudinal studies are not always feasible, and the results from in vitro and in vivo experiments cannot be applied directly to humans. Mendelian randomization (MR) provides a different method to overcome these limitations. MR uses single-nucleotide polymorphisms (SNPs) as instrumental variables (IVs) for exposures and ensures that they are independent of environmental factors and the disease process, reducing the impact of reverse causation and confounders on the results. It offers an alternative approach to alleviate the limitations of traditional studies by using the random distribution of alleles during gametogenesis and conception to approximate randomized controlled trials [Citation15]. Therefore, the present study examined the causal associations between interleukin receptor-related factors and the susceptibility to develop endometriosis by applying a two-sample MR analysis by integrating publicly available datasets. The results could help elucidate both the pathogenesis of endometriosis and suggest possible therapeutic targets.

Study reporting guidelines and study design The study was reported based on the Strengthening the Reporting of Observational Studies in Epidemiology using Mendelian Randomization (STROBE-MR) statement [Citation16]. A two-sample MR approach was employed to examine the causal relationship between interleukin receptor-related factors, the risk of developing endometriosis, and the mediating role of immune cells in its pathogenesis. The assumptions for MR analysis validity are 1) the relevance assumption (i.e. the SNPs being used as IVs for the exposure are associated with the exposure), 2) the independence assumption (i.e. there are no common causes between the SNPs and the outcome of interest), and 3) the no horizontal pleiotropy assumption (i.e. there are no independent pathways between the SNPs and the outcome other than through the exposure) [Citation28] (). MR studies are based on publicly available data from genome-wide association studies (GWASs), and ethical approval was unnecessary. Data sources The GWAS data were downloaded from the open GWAS website (https://gwas.mrcieu.ac.uk/) [Citation17]. GWAS data associated with interleukin receptors were identified by searching ‘interleukin’ in the trait column of the available GWAS datasets. Data of individuals from European ancestry were retained for subsequent analyses. The GWAS data on endometriosis (finn-b-N14_ENDOMETRIOSIS; 8288 cases and 68,969 controls) were obtained by searching ‘endometriosis’ in the trait column of the downloaded GWAS data. The GWAS data for the interleukin receptor-related factors prot-a-1530 (interleukin-3 receptor subunit alpha (IL-3Rα); 3301 individuals; 10,534,735 SNPs), prot-a-1542 (interleukin-6 receptor subunit beta (IL-6Rβ); 3301 individuals; 10,534,735 SNPs), and prot-b-38 (interleukin-1 receptor-like 1 (IL-1RL1); 3394 individuals; 5,270,646 SNPs) were from two published studies [Citation18,Citation19] (). All data were obtained in March 2024. The risk factors for endometriosis were identified by literature review, and GWAS data for body mass index (BMI), smoke, and alcohol were obtained from GWAS datasets from European individuals. Finally, the list of immune cells was obtained from the literature on interleukin receptor-related factors [Citation20]. Hence, a list of 731 immune cells (Table S1) was obtained, and the GWAS datasets from individuals of European ancestry were downloaded from GWAS datasets. Selection and strength evaluation of instrumental variables Three key assumptions must be met for a SNP to be considered a valid IV for MR. Firstly, the chosen IV must demonstrate a significant association with the exposure. Secondly, the IV must not be significantly associated with potential confounders that could affect the exposure and the outcome. Thirdly, the effect of the IV on the outcome can only occur via exposure [Citation21]. Therefore, the following criteria were used to select SNPs for IVs. SNPs with a significance level of p < 5 × 10−8 from the exposure GWAS were selected [Citation22]. SNPs in linkage disequilibrium (with r2 10,000 kb between each pair of genes) were excluded [Citation23]. Consequently, the outcome GWAS data were obtained using the selected SNPs [Citation24]. The F-value was calculated to evaluate the potential bias from weak IVs [Citation25]. If F < 10, it indicated a weak instrumental variable that might lead to bias in the results [Citation26], and it was necessary to exclude it to avoid any impact on the findings. The formula employed to compute the F-value was [Citation27] where N is the sample size, k is the number quantity of IVs employed, and R2 indicates the degree to which the instrumental variables account for the exposure, which was calculated using where MAF is the minimum allele frequency, and β is the allele effect size. MR causal effect estimation Multiple two-sample MR methods, including the inverse variance weighted (IVW), MR-Egger, weighted median (WM), simple mode, and weighted mode methods, were used to investigate the causal associations of interleukin receptor-related factors on endometriosis. The main method employed in this study was the IVW method, which utilizes meta-analysis to estimate the overall exposure-outcome effect [Citation28]. The WM and MR-Egger methods were used as supplementary tests for MR estimation [Citation29,Citation30]. The WM method is more effective when half of the genetic variants are invalid [Citation30]. The MR-Egger method assessed the independence of instrumental variable strength from the direct effects hypothesis, which assumes that horizontal pleiotropy effects are unrelated to the association between the variable and exposure [Citation29]. Horizontal pleiotropy was considered significant when p < 0.05. The IVW method has demonstrated slightly higher efficacy than other methods in certain conditions [Citation30]. IVW possesses unique features, including excluding the intercept term in regression and using the inverse of the outcome variance as the fitting weight. In the absence of pleiotropy and regardless of heterogeneity, the IVW method was used as the main MR analysis, supported by the other four methods (with the IVW random effects model applied in the presence of heterogeneity). The MR-Egger method was used to calculate the results in the context of pleiotropy. The Steiger directivity test was used to ascertain the direction of causality [Citation31]. The potential causal effect of the outcome of the exposure was assessed using the same method to evaluate reverse causality. Sensitivity analysis Sensitivity analysis involved conducting a heterogeneity test, a pleiotropy test, and an individual exclusion test. Firstly, the heterogeneity test was performed using the Cochran Q test to evaluate the differences among individual SNP estimates [Citation32]. The results of the Cochran Q test revealed considerable heterogeneity, which indicated considerable variation across the analysis results. The Cochran Q test solely assessed whether heterogeneity was present or not. The I2 statistic was used to quantify the proportion of heterogeneity within the total variation. I2 ≤ 0 indicated the absence of heterogeneity, I2 = 0-25% suggested moderate heterogeneity, I2 = 25%-50% indicated moderate heterogeneity, and I2 > 50% indicated high heterogeneity. The specific calculation was [Citation33] The pleiotropy test involved using the MR-Egger regression method to assess the pleiotropy among IVs [Citation32]. A P value of the MR-Egger’s intercept < 0.05 suggests significant horizontal pleiotropy is associated with the SNPs. Thirdly, the leave-one-out test was conducted by calculating the MR results after excluding each SNP [Citation33]. Any significant difference between the MR effect estimate and the overall effect estimate after excluding an IV indicates the sensitivity of the MR effect estimate to a specific SNP. Multivariable mendelian randomization analysis and estimation of mediating effects Multivariable Mendelian randomization (MVMR) is an extension of MR that utilizes SNPs associated with multiple potentially correlated exposures to evaluate the impacts of these exposures on a single outcome. It can assess the direct effects of one exposure on the outcome. These effects were evaluated using multiple risk factors associated with endometriosis (BMI, smoking, and alcohol). Interleukin receptor-associated factors were subjected to individual and global multivariable MR analyses to obtain the direct effect of interleukin receptor-associated factors on endometriosis. The indirect effects of the interleukin receptor-related factor on immune cells and endometriosis were obtained from the effects of screened interleukin receptor-related factors on immune cells (). The effect sizes and standard errors for mediating effects were calculated according to the following equation [Citation34]: where βM affects the value of the mediating effect, βA is the MR effect value of interleukin receptor-related factors on immune cells, βB is the direct effect value of immune cells on endometriosis (obtained by MVMR), SEM is the standard error of the mediating effect, SEA is the standard error of MR analysis of interleukin receptor-related factors on immune cells, and SEB is the standard error of MR analysis of immune cells in endometriosis. Statistical analysis All calculations and statistical analyses were performed using R programming (version 4.2.2) [https://www.r-project.org/]. The two-sample MR package [Citation31] was employed for MR analysis. In the MR analysis of exposure and outcome, the measure of association was presented as odds ratios (OR) with a 95% confidence interval (95% CI). SNPs with p < 5 × 10−8 from the GWAS datasets were considered statistically significant. For the other analyses, two-sided P-values < 0.05 were considered statistically significant.

Screening of instrumental variables According to this study’s IV selection criteria, the SNPs with linkage disequilibrium were excluded. Following the alignment of the GWAS data for endometriosis (finn-b-N14_ENDOMETRIOSIS), SNPs associated with interleukin receptor-related factors were included as IVs. presents the results of the IV screening for each exposure, showing only the indicators that were found to be significant through MR analysis. The F-value for the IVs exceeded 10, suggesting that the majority of the SNPs chosen in this study were strong IVs, thereby minimizing the potential bias associated with weak IVs. Causal associations of interleukin receptor-associated factors on endometriosis The IVW results showed that the three selected interleukin receptor-related factors (prot-a-1542, prot-a-1530, and prot-b-38) had significant causal associations with endometriosis (prot-a-1542: OR = 0.832, 95%CI: 0.698-0.994, p = 0.039; prot-a-1530: OR = 0.913, 95%CI: 0.852-0.978, p = 0.009; prot-b-38: OR = 1.077, 95%CI: 1.004-1.154, p = 0.037) (). In addition, the results of MR analysis of interleukin receptor-related factors and endometriosis (finn-b-N14_ENDOMETRIOSIS) were presented as forest plots (). shows the linear relationship between the effect of interleukin receptor-related factors and the effect on endometriosis occurrence under the five methods. The findings indicate that the direction of the effect size estimated by MR Egger, WM, simple mode, and weighted mode aligned with that of the IVW method. The slope represented the value of β, which reflects the degree of linear dependence between the instrumental variables regarding the effects on both the exposure and the outcome. Then, Cochran’s Q-test and I2 values were used to test the heterogeneity of the MR Egger and IVW model results. Prot-a-1530 and prot-b-38 showed no heterogeneity in the MR results of endometriosis (Cochran Q p-value > 0.05) (Table S2). Leave-one-out analysis was employed to exclude each IV locus to assess the impact of interleukin receptor-related factors and the causal effect of endometriosis (). No significant deviation was found from the lump effect of IVs. The funnel plots () for the IVs related to interleukin receptor factors demonstrated that the distribution of causal effects was symmetrical, suggesting no potential bias in the results. Next, MR-Egger regression was used to assess the level of pleiotropy in the IVs. The statistical hypothesis test for the intercept term concerning interleukin receptor-related factors resulted in a P-value of > 0.05, and since the intercept was around 0, it suggested that the causal inference of this study was not affected by the level of pleiotropy (). Finally, the Steiger directivity test was used to determine whether the causal direction of interleukin receptor-related factors to endometriosis (finn-b-N14_ENDOMETRIOSIS) was correct (). The Steiger directional test calculated SNPs’ variance explanation rate (r2) for exposure and outcome. The results showed that the SNPs of the selected index explained more variance for exposure than for outcome, with the direction of TRUE and p < 0.05, indicating that the direction was correct. Causal associations of endometriosis on interleukin receptor-associated factors (reverse analysis) The IVW results indicated no significant causal association associations between endometriosis as exposure and interleukin receptor-related factors as outcomes (). MVMR analysis of interleukin receptor-related factors for the onset of endometriosis The risk factors associated with endometriosis, including body mass index, smoking, and alcohol, and two interleukin receptor-related factors (prot-a-1530 and prot-b-38) were used to assess the direct effect of interleukin receptor-related factors on endometriosis. First, the MVMR models were constructed by combining each endometriosis risk factor (BMI, smoking, and alcohol) with the two interleukin receptor-related factors to predict the relationship between endometriosis risk factors and outcomes (Table S3). Twelve of these MR models were randomly presented (). The results showed that after adjusting for BMI alone, the two interleukin receptor-related factors still significantly affected endometriosis. After adjusting for smoking alone, the two interleukin receptor-related factors continued to have a significant impact on endometriosis. Similarly, after adjusting for alcohol alone, the two interleukin receptor-related factors still had a significant effect on endometriosis. Mediation effect analysis First, a Steiger directivity test was performed to determine whether the causal direction of the interleukin receptor-related factors (prot-a-1530 and prot-b-38) to the 75 selected immune cells was correct (Table S4). The results showed that the SNPs of the selected indicators had a greater variance explanation rate for exposure than for the outcome risk factors, and the direction was TRUE, with p < 0.05, indicating that the direction was correct. After that, the mediating effect of the model was evaluated, in which the mediating factors demonstrated a significant causal association with the outcome of the MVMR analysis. The significant effect of prot-b-38 on endometriosis in model 6 (p < 0.05) suggests that prot-b-38 affects endometriosis through immune cells (ebi-a-GCST90001951). A partial mediating effect model was constructed. The results of the Sobel test (Table S5) showed that the mediating effects of the other models were non-significant except for Models 2, 9, and 6. According to the findings of univariable MR analysis, the causal effect value of interleukin receptor-related factors on immune cells was obtained, and the direct and indirect effect values of immune cells on endometriosis were obtained using MVMR analysis. The mediating effect value of interleukin receptor-related factors on the pathogenesis of endometriosis through immune cells was calculated. The results are presented in . They indicated that the interleukin receptors-related factor prot-b-38 in immune cells (ebi-a-GCST90001951) had indirect effects on endometriosis with a factor of 0.00206, and the indirect to direct effect ratio was 6.38% (0.00471/0.06909 × 100%).

The results revealed significant causal associations between interleukin receptor-associated factors IL-6Rβ, IL-3Rα, and IL-1RL1 and endometriosis, but the reverse MR analysis indicated that endometriosis did not significantly affect those proteins. The associations remained significant for IL-3Rα and IL-1RL1 after adjusting for confounders in the MVMR analysis. Furthermore, immune cells (ebi-a-GCST90001951) appeared to mediate the relationship between IL-1RL1 and endometriosis. Therefore, this study offers novel insights into the mechanisms of endometriosis that may contribute to endometriosis pathophysiology independently of BMI, alcohol, and tobacco. While the etiology of endometriosis remains unclear, several theories have been proposed as to its pathogenesis. The most common theory is retrograde menstruation, resulting in the implantation of refluxed menstrual tissue on pelvic and intrabdominal structures [Citation7,Citation8,Citation35]. Other theories include 1) metaplasia of mesothelial cells that cover the peritoneum, which is known as the coelomic-metaplasia theory, 2) metastatic spread of endometrial tissue through the lymphatic and/or venous systems, 3) rectovaginal Mullerian remnants, 4) ectopic placement of embryonic endometrial tissue during organ development and formation, which is known as the Mullerianosis hypothesis, and altered immune cell activity and population, which impairs the clearance of ectopic tissue and differentiation of endometriotic tissue and promotes adherence/invasion, angiogenesis, and sensory, sympathetic, or parasympathetic stimulation [Citation7,Citation8,Citation35]. Nevertheless, irrespective of the reason for its ectopic presence, endometrial tissue outside the uterus triggers a chronic, estrogen-stimulated inflammatory response. Inflammation of the endometriotic lesions may result in associated pain and subfertility [Citation6,Citation7,Citation35]. Inflammation from the overproduction of cytokines, prostaglandins, and inflammatory substances creates central nervous system sensitization and triggers a pain response. Cytokines and inflammatory factors and products can contribute to pain and the proliferation of endometriotic lesions [Citation36]. In advanced cases, lesions may impair tuboovarian function and lead to distorted ovum release, pickup, and poor ovarian reserve/quality. Progesterone resistance may amplify the effects of estrogen, which promotes the chronic persistence and growth of endometrial lesions. In endometriosis, apoptosis is impaired, particularly in ectopic endometrial tissue, contributing to the disease’s development and progression. This reduced susceptibility to apoptosis allows endometriotic cells to survive and proliferate outside the uterus [Citation37–39]. Apoptosis also appears to play a role in the severity of endometriotic lesions [Citation40]. Infertility is common in patients with endometriosis, which can occur due to 1) mechanical obstruction by pelvic adhesions, 2) dysfunctional interactions between sperm and fallopian tube epithelium, 3) tubal damage, 4) local and systemic inflammatory processes with increased cytokine levels in peritoneal fluid that inhibits folliculogenesis and spermatozoa transportation and transplantation, including inhibited ciliary beat frequency, 5) altered hormonal levels, including changes in the pituitary-ovarian axis function resulting in extended follicular phase and abnormalities in luteinizing hormone secretion, and 6) genetic polymorphisms, which may include elevated mRNA expression of transcriptional factor Foxp3 and increased expression of CXCL1, CX3CL1, CXCL9, CXCL10, IL-32, CXCR2, IL-7R, ICAM-1, and SELL [Citation6,Citation41,Citation42]. The present study is the first MR study to elucidate the causal associations between interleukin receptor-related factors and the risk of developing endometriosis, emphasizing the mediating role of immune cells. The findings confirm significant causal associations between interleukin receptor-related factors, particularly IL-6Rβ, IL-3Rα, and IL-1RL1, which have significant causal associations with endometriosis. These findings are supported by Sapkota et al. [Citation43] and Lin et al. [Citation44], who established the involvement of cytokine signaling pathways in the pathogenesis of endometriosis using GWASs. The present study strengthens the evidence of this involvement by using robust MR methods, as consistent results were obtained through multiple analysis models. Conversely, the reverse MR analysis suggested that the onset of endometriosis does not significantly alter the levels of interleukin receptor-related factors IL-3Rα and IL-1RL1. The lack of bidirectional causality implies that alterations in these cell cytokine receptors may contribute to the onset of the disease rather than being a consequence of disease progression. This finding contrasts with the study by Lee et al. [Citation45], who reported a potential bidirectional relationship between inflammatory markers and endometriosis using a smaller case-control dataset. This difference may be attributed to differences in study design or population heterogeneity. The MVMR and IVW analysis showed that even after adjusting for confounding factors such as BMI, smoking status, and alcohol consumption, IL-3Rα and IL-1RL1 remained significantly causally associated with endometriosis. These findings are supported by recent studies that indicated that after considering lifestyle factors, cytokine signaling can significantly influence the inflammatory environment of endometriosis [Citation9,Citation46–49]. Indeed, although endometriosis has cyclic symptoms that align with the menstrual cycle [Citation50], the inflammation caused by the endometriosis lesions within the abdominal cavity is responsible for the pain and other symptoms [Citation51]. Interestingly, the present study suggested that immune cell ebi-a-GCST90001951 (CD33 on CD66b++ myeloid cell) mediates the causal association between IL-1RL1 and endometriosis. Although the involvement of CD33+ and CD66b + cells has been described in endometriosis [Citation52], no previous studies reported the involvement of the precise CD33 on CD66b++ myeloid cell trait. Nevertheless, myeloid-derived suppressor cells have been shown to be regulated by estradiol [Citation53], which is involved in the pathophysiology of endometriosis [Citation54]. Hence, those results raise interesting questions about the involvement of specific immune cell populations in endometriosis. Furthermore, the involvement of interleukin 1 in endometriosis has been identified previously through the interleukin 1 receptor types 1 and 2 [Citation55]. IL1RL1 has been shown to be associated with endometriosis in the context of paraben and benzophenone exposure [Citation56]. The Sobel test indicated that the indirect effect accounted for approximately 6.38% of the total effect. It is consistent with experimental studies suggesting the involvement of immune cells in cytokine signaling associated with endometriosis [Citation57,Citation58]. It indicates that specific types of immune cells may be essential links between cytokine receptors and endometriosis [Citation59]. Understanding this mediating effect can open up new avenues for research on immune regulatory interventions in patients with endometriosis. The present study offers new perspectives on the pathogenesis of endometriosis by establishing crucial causal associations between interleukin receptor-related factors and endometriosis. Previous studies have primarily focused on epidemiological association evidence, which cannot provide causality evidence. In contrast, the present two-sample MR analysis allows for causal inference. The sensitivity analyses further confirmed the stability of the results, including the heterogeneity test and pleiotropy assessment. These analyses alleviated the bias commonly observed in observational studies due to confounding variables. Moreover, the study enhanced the understanding of the disease by employing MVMR analysis to adjust for known risk factors such as BMI, smoking, and alcohol. In addition, the Sobel test could confirm the importance of the mediating effect between immune cell ebi-a-GCST90001951, IL-1RL1, and endometriosis. Regarding the limitations, the findings were solely based on bioinformatics analysis and lacked experimental validation. In addition, although the sample size used in the analysis is sufficient, it may not capture the full spectrum of genetic factors associated with endometriosis, potentially limiting the generalizability of our findings. Indeed, all individuals were of European ancestry, and the results might not be applicable to populations with another genetic background (e.g. Asians). Furthermore, using multiple datasets may introduce batch effects, and it may impact the results.

This MR study revealed causal associations between IL-6Rβ, IL-3Rα, and IL-1RL1 and the risk of developing endometriosis. The causal associations between IL-3Rα and IL-1RL1 and endometriosis were independent of BMI, smoking, and alcohol. Specific immune cells could mediate the causal associations between interleukin receptor-related factors and endometriosis development, warranting additional studies. The results provide a foundation for future research into the pathogenesis, pathophysiology, and therapeutic targets of endometriosis. Supplemental material Table S2 Heterogeneity Assessment of MR Egger and IVW Model Results.xlsx Download MS Excel (21.7 KB)Table S2 Heterogeneity Assessment of MR Egger and IVW Model Results.xlsxTable S1 List of 731 Immune Cell Types Analyzed in the Study.xlsx Download MS Excel (92.3 KB)Table S1 List of 731 Immune Cell Types Analyzed in the Study.xlsxTable S4 Steiger Directivity Test for Causal Direction of Interleukin Receptor Related Factors to Selected Immune Cells.xlsx Download MS Excel (29.3 KB)Table S4 Steiger Directivity Test for Causal Direction of Interleukin Receptor Related Factors to Selected Immune Cells.xlsxTable S5 Sobel Test Results for Mediating Effects in Partial Mediation Models.xlsx Download MS Excel (28.1 KB)Table S5 Sobel Test Results for Mediating Effects in Partial Mediation Models.xlsxTable S3 MVMR Model Analysis of Endometriosis Risk Factors and Interleukin Receptor Related Factors.xlsx Download MS Excel (31.1 KB)Table S3 MVMR Model Analysis of Endometriosis Risk Factors and Interleukin Receptor Related Factors.xlsxAcknowledgments The authors are thankful to Shanghai First Maternity and Infant Hospital and Tongji University for the successful completion of this research. Si-ji Lv carried out the study, participated in the analysis, and drafted the manuscript. Qing Yuan performed the statistical analysis and participated in its design. Shan-shan Zong participated in the investigation, analysis, and draft of the manuscript. Lei Ye conceptualized and supervised the study. Disclosure statement No potential conflict of interest was reported by the author(s). Data availability statement The datasets generated and analyzed in this study are available on the open GWAS website (https://gwas.mrcieu.ac.uk/). Additional information Funding

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