To Örebro University

Background: Microscopic colitis (MC), comprising collagenous colitis (CC) and lymphocytic colitis (LC), is a type of variation of inflammatory bowel diseases. Local T-cell infiltration in the mucosa plays a major role in MC immunopathology.

Methods: To understand diversity and clonality of infiltrating T cells, we analyzed the T-cell receptor beta (TCR beta) chains in colonic biopsies of MC, ulcerative colitis (UC), and their remission counterparts (CC/LC-HR [histological remission] or UC-R [remission]) compared with patients with non-inflamed colons using next-generation sequencing.

Results: Compared with controls and patients with CC, patients with LC had significantly lower diversity with significantly lower evenness and richness in TCRVb-Jb gene segments. Similarly, patients with LC-HR had lower diversity because of significantly lower TCRVb-Jb clone richness. Patients with UC and UC-R showed significantly higher diversity and richness. Univariate and multivariate analyses were performed to identify TCRVb-Jb gene segments differentiating disease types from controls or their remission counterparts. Patients with LC were discriminated from controls by 12 clones and from patients with CC by 8 clones. Neither univariate nor multivariate analyses showed significance for patients with CC or CC-HR compared with controls. Patients with UC and UC-R had 16 and 14 discriminating clones, respectively, compared with controls.

Conclusions: Altogether, patients with MC and UC showed an oligoclonal TCRb distribution. TCRVb-Jb clone types and their diversity were distinctive between patients with CC and LC, as well as for patients with UC, suggesting different pathophysiological mechanisms according to disease type and stage. This study suggests that CC and LC are different entities because of differences in immunoregulatory responses, as mirrored by their T-cell repertoire.