IgG4 and IgG-positive plasma cell infiltration and high correlation with disease activity in patients with inflammatory bowel disease undergoing colectomy

Background: The aims of this study were to identify the distribution and the role of IgG-positive and IgG4-positive plasma cell infiltration in colonic mucosa in patients with inflammatory bowel disease (IBD). Methods Patients with IBD who were free from immunosuppressive agents were consecutively enrolled from 2010 to 2014. Sections from surgical specimens were stained with monoclonal antihuman IgG4 and IgG antibody using standard immunohistochemical techniques. Results In total, 49 patients (30 CD and 19 UC) were included in this study. There was abundant infiltration of IgG4-positive plasma cells in 4 patients with UC (IgG4-present, 21.1%) and 6 patients with CD (IgG4-present, 20.0%). A significantly higher number of IgG-positive cells and IgG4-positive cells were found in patients with CD and UC than in control group. Higher proportions of IgG4 correlated with higher endoscopic activity scoring, higher revised Mayo score, lower haemoglobin, higher erythrocyte sedimentation rate, higher high sensitive C-reactive protein (hsCRP) and higher D-dimer in patients with UC (P < 0.05). A significant difference was identified in terms of disease activity in the IgG-present group compared with the group with the IgG-absent group (69.2% vs 16.7% P  < 0.05). If the cut-off value was set at 25 cells/HPF for IgG, the sensitivity and specificity of predicting severity potential in UC was 90.0% and 55.6%, respectively. The area under the curve was 0.633 by receiver operating characteristic analysis. Conclusions These findings suggest that IgG4 infiltration appears to be a relevant marker of inflammatory process caused by immune dysregulation in patients with IBD.