Activation of human lamina propria mononuclear cells in inflammatory bowel disease

The state of activation of human lamina propria mononuclear cells (LPMnc) obtained from either organ transplant donors or from operation specimens from inflammatory bowel disease (IBD) patients were studied by three-color fluorescence activated cell sorting (FACS). Freshly isolated LPMnc from normal donors as well as from IBD patients were autofluoresent. The autofluorescence could be subtracted from the FACS data on a cell-by-cell basis by a mathematical post processing step. Normal LPMnc are in vivo activated and express increased levels of 4F2-antigen, transferrin and interleukin-2 receptor. The number of lymphocytes, which express these early activation antigens was markedly increased in both Ulcerative Colitis (U.C.) and Crohn’s disease (C.D.). This underlines the hypothesis of a major upregulation of the mucosal immune system due to the disease process. B cells in particular were activated, suggesting they may be of particular importance in the disease process of IBD.