Surface antigens of the murine cytostatic peritoneal macrophage.

By rosetting techniques, peritoneal exudate cells (PEC) from mice stimulated intraperitoneally with starch have been shown to be a mixed population of cells consisting of the following subpopulations of cells: 75% FcR, 26% C3R, 18% Ig+, 29% Ia+, Ig- and 5% Thy-1+, Ig-. By separating rosetting from non-rosetting cells, it was possible to establish the phenotype of the PEC which was cytostatic for tumour cells. This cell possessed receptors for Fc and C3 but lacked surface Ig, the Thy-1 antigen and I-region controlled antigens and was NSE positive. Thus by presently available criteria, the cytostatic PEC can be identified as a macrophage. The lack of Ia distinguishes this type of macrophage from the antigen-presenting macrophage which bears Ia.