The macrophage population of the gastro-intestinal tract of the rat

The macrophage population of the gastro-intestinal tract of the rat was studied by using a set of three monoclonal antibodies (ED1, ED2 and ED3) directed against rat macrophages, an anti-Ia monoclonal antibody and by performing an acid phosphatase reaction. The lamina propria of the whole gastro-intestinal tract comprised quite high numbers of macrophages. This macrophage population was heterogeneous. The Ia-positivity and the acid phosphatase activity of the macrophages were higher in the intestines than in the stomach and esophagus. ED1-positive macrophages were also quite numerous in the intestines; their number was relatively low in the esophagus and stomach. ED2-positive macrophages were found equally dispersed along the gastro-intestinal tract; ED3-positive cells were hardly found. The functional implications of the present findings are discussed.