Interleukin 2 receptor expression by macrophages in inflammatory bowel disease

The expression of interleukin 2 receptor by macrophages from normal and inflamed terminal ileum and colon has been studied by using two monoclonal antibodies. In tissue sections from normal ileum and colon, scattered positive lymphocytes and only occasional weakly positive macrophages were seen. In ileal and colonic Crohn's disease or ulcerative colitis many positive macrophages and lymphocytes were seen in the lamina propria. These findings were confirmed by staining cytospin preparations of isolated intestinal mononuclear cells. The isolated macrophages were able to phagocytose opsonized zymosan and the majority were able to undergo a respiratory burst when triggered with opsonized zymosan or phorbol myristate acetate (PMA), suggesting that they were activated. Stimulation with interferon-gamma or lipopolysaccharide did not increase the number of macrophages staining with the antibodies to the interleukin 2 receptor. Therefore we postulate that a large majority of the macrophages expressing interleukin 2 receptor in inflammatory bowel disease are a recently recruited population of cells.