Rosette formation by mouse lymphocytes. IV. Fc and C3 receptors occurring together and separately on T cells and other leucocytes.

A method is described for detecting the simultaneous presence of Fc and C3 receptors on mouse spleen cells. A proportion of both T cells and non-T cells bear both receptors. Both T-cell and non-T-cell Fc receptors were blocked by aggregated mouse IgG2 to the same degree. C3, but not Fc, receptors were blocked by factors present in the serum of irradiated mice or mice undergoing graft-versus-host reaction. Thymocytes activated by injection into irradiated F1 hybrid mice, and thymocytes regenerating after irradiation and bone marrow injection, appeared to have increased Fc receptors. A general role for Fc and C3 receptors in T cell-B cell co-operation is suggested.