Objectives: An increase of intraepithelial lymphocytes (IEL) is commonly found in lymphocytic colitis (LC) and collagenous colitis (CC), and has also been observed in the colonic mucosa of some patients with celiac disease or celiac-like disease. Thus, a similar mechanism could play a role in these apparently different entities. The aim of this work was to determine the phenotype of IEL and of lamina propria lymphocytes in the setting of LC and CC.
Methods: Biopsies were taken from all segments of the large bowel and from the ileon of eight patients with CC, four patients with LC, and 10 controls. An immunohistochemical study using monoclonal antibodies directed against IEL, T-cells, helper T-cells, suppressor/cytotoxic T-cells, HLA DR antigens, T-cell-bearing T-cell receptor (TcR) alpha beta, and TcR gamma delta was carried out.
Results: There was an increased in mean numbers of IELs in both LC and CC, with significantly more CD 8 IELs than CD 4 IELs. Most IELs were bearing TcR alpha beta; TcR gamma delta-bearing cells were not increased in CC or LC. CD 4+ helper T-cells predominated in the lamina propria. Epithelial cells of colonic mucosa abnormally expressed HLA DR antigens. There were no significant differences between findings in LC and CC.
Conclusion: This study suggests that the immune abnormalities are similar in LC and CC and that a MHC-restricted immune mechanism could be involved in both diseases. Evidence for this includes: 1) the accumulation of CD 4+ T-cells within the lamina propria, 2) epithelial damage closely related to the increase of CD 8 TcR alpha beta IELs, and 3) abnormal class II MHC molecule expression on epithelial cells of colonic mucosa. Furthermore, the results suggest that the putative immune mechanisms underlying LC or CC are probably different from those that are incriminated in celiac disease.