MHC Class II expression (labelled with TIB 120) in healthy colonic tissue (control). Epithelial cells do not express this antigen. Expression is increased in inflamed colonic tissue at day 8 of DSS ingestion. Positive cells can also be found concentrated in the lymphoid follicle and there is expression on epithelial cells. 2.5% DSS-induced colitis. Findings from inflamed colons of 5%DSS-induced colitis were similar. Original magnification × 20.