Microscopic colitis patients have increased proportions of Ki67(+) proliferating and CD45RO(+) active/memory CD8(+)...

Collagenous colitis (CC) and lymphocytic colitis (LC) are chronic inflammatory bowel disorders of unknown etiology. This study investigated phenotypic characteristics of the mucosal lymphocytes in CC and LC.

Lamina propria and intraepithelial lymphocytes (LPLs, IELs) isolated from mucosal biopsies from CC (n=7), LC (n=6), as well as LC or CC patients in histopathological remission, (LC-HR) (n=6) and CC-HR (n=4) and non-inflamed controls (n=10) were phenotypically characterized by four-color flow cytometry.

The proportions of CD8(+) IELs were increased in CC and LC (p<0.01) compared to controls. Increased proportions of CD45RO(+)CD8(+) IELs and LPLs were observed in LC and even more in CC patients (p<0.01). Both CC (p<0.05) and LC patients had elevated proportions of CD4(+)8(+) IELs and LPLs compared to controls. The proportions of CD45RO(+) cells were increased in CD4(+)8(+) IELs and LPLs (p<0.05) in CC and LC patients compared to controls. Both CC (p<0.05) and LC patients had higher proportions of Ki67(+)CD8(+) IELs and LPLs compared to controls. In contrast, decreased proportions of CD4(+) LPLs were observed in CC and LC as well as CD4(+) IELs in LC compared to controls. Increased proportions of Ki67(+)CD4(+) IELs and LPLs (p<0.05) were observed in CC and LC patients. CC-HR but not LC-HR patients demonstrated normalized proportions of both IELs and LPLs compared to CC and LC patients respectively.

LC and CC patients have differences in mucosal lymphocyte subsets, with increased proportions of Ki67(+) and CD45RO(+) CD8(+) and CD4(+)8(+) mucosal T cells.