The fate of cell surface I-Akand H-2Kkantigens shed by murine spleen cells in culture was studied by incubation of nonlabeled spleen cells or splenic T or B cells with culture fluids containing shed radiolabeled alloantigens. Approximately 30 to 40% of the shed alloantigens could be absorbed by syngeneic or allogeneic murine T cells, B cells, or macrophages, but not by heterologous erythrocytes or human peripheral blood lymphocytes. Absorption was dependent on temperature and lipids associated with the shed glycoproteins. Once absorbed, the alloantigens were catabolized by the absorbing cells with a half-life of approximately 4 hr. It is suggested that absorption of shed cell surface alloantigens may be a vehicle for intercellular communication in the immune system.