CD200 receptor and macrophage function in the intestine.

CD200 receptor 1 is an inhibitory receptor expressed by myeloid cells which has inhibitory effects on macrophage function after binding its ubiquitously expressed ligand CD200. Recent evidence suggests that this is important in controlling inflammatory reactions in the lung and here we have explored if the CD200R1-CD200 axis plays a similar role in other mucosal surfaces such as the intestine. We show for the first time that CD200R1 is expressed selectively by resident macrophages in normal mouse colon and that CD200 is present on many haematopoietic and non-haematopoietic cells in the intestine. Although acute colitis induced by feeding dextran sodium sulphate is associated with an influx of CD200R1(neg) macrophages, CD200R1 KO mice have normal macrophage function in the colon and they do not develop spontaneous intestinal inflammation, nor are they more susceptible to DSS colitis. CD200 KO mice also develop experimental colitis normally and we conclude that CD200R1 does not play an essential role in macrophage homeostasis in the colon, indicating that these molecules may have distinct functions in different mucosal tissues.