| Abstract: | Background: IgA, the primary immunoglobulin secreted by gut B cells, plays a key role in defending against pathogen invasion. Elevated plasma IgA levels have been observed in inflammatory bowel disease (IBD) patients, particularly those undergoing biologic therapy. However, direct evidence linking plasma IgA levels to bowel wall inflammation is lacking. This study investigates the relationship between plasma IgA levels and intestinal inflammation, using parameters from intestinal ultrasound (IUS). Methods: We enrolled 30 IBD patients (20 with ulcerative colitis (UC) and 10 with Crohn’s disease (CD)) for IUS evaluation starting in July 2023. Ultrasound scores were based on the Milan ultrasound criteria (MUC) for UC and the bowel ultrasound score (BUSS) for CD. Plasma levels of ESR, CRP, albumin, IgA, partial Mayo score, and CDAI were collected at baseline, during treatment, and after 52 weeks of advanced therapy (Adalimumab, Vedolizumab, or Tofacitinib). IUS findings and plasma IgA levels were analyzed for correlations with clinical parameters using the Student’s t-test and linear regression. Results: IUS findings were closely correlated with disease activity. In UC, the MUC score was positively correlated with CRP (P < 0.0001, R² = 0.4888), partial Mayo score (P = 0.0002, R² = 0.3652), and negatively with albumin levels (P = 0.0002, R² = 0.3747). In CD, the BUSS score showed a positive correlation with CDAI (P = 0.0394, R² = 0.2694). Plasma IgA levels were significantly associated with bowel wall thickness (BWT) in both UC and CD (P = 0.0041, R² = 0.1759) (Figure 1). Notably, when BWT exceeded 3.5 mm, plasma IgA levels increased significantly (P = 0.0021) (Figure 2). Interestingly, in CD, plasma IgA was strongly correlated with the BUSS score (P = 0.0001, R² = 0.6585), while no such relationship was observed between MUC score and plasma IgA in UC. Conclusion: Plasma IgA levels are positively correlated with bowel wall thickness in both UC and CD patients, particularly when BWT exceeds 3.5 mm. In CD patients, IgA levels also show a strong correlation with the BUSS score, highlighting IgA as a potential biomarker for bowel wall inflammation. These findings suggest that plasma IgA could serve as a biomarker of disease activity, particularly in CD, and could aid in monitoring therapeutic response and disease progression in IBD. Further research is warranted to validate these results and explore the potential for IgA-targeted therapies. |
