Colonic mucosal T lymphocytes in ulcerative colitis: Expression of CD7 antigen in relation to MHC class II (HLA-D) antigens

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Abstract
T-cell subsets and their activation state were examined by double-label immunofluorescence of cryostat tissue sections of the colon from 21 patients with ulcerative colitis (UC) and 30 histologically normal controls. Expression of MHC class I (HLA-A, B, C) and class II (HLA-D) antigens was studied in parallel. In the normal colonic mucosa, the CD4∶CD8 ratio in the epithelial compartment approximated 1∶1, and in the lamina propria, 2.55∶1. Of the CD8+ (cytotoxic/suppressor) subset, approximately half did not express the CD5 “pan-T” marker in either compartment. Virtually no Leu 8+ cells were observed, implying that the CD4+ subset consisted of helper, rather than suppressor-inducer cells. Classical markers of T-cell activation (CD25, HLA-D) and proliferation were absent, and strong expression of the CD7 “immunostimulation” marker was approximately equal in both CD4 and CD8 subsets. The epithelium was uniformly negative for class II antigens, but positive for class I. In UC, there were no significant alterations in CD4∶CD8 ratios in either compartment, and there were no changes with respect to phenotype of the subsets. In 11 of 19 patients (mainly with total colitis), enterocytes were HLA-D+. In this HLA-D+ group, there was an increase in the percentage of CD4+ cells coexpressing CD7; this difference was significant (P+ T cell subset (P<0.05). These results suggest that class II expression is mediated by immunostimulated T helper cells in UC, with consequences for antigen presentation and maintenance of the chronic inflammatory state.