Expression of C4 on Human Lymphoid Cells and Possible Involvement in Immune Recognition Phenomena

Abstract
Immunochemical studies revealed the presence of the fourth component of complement (C4) on surfaces of human lymphoid cells. Antiserums to C4 inhibited the mixed lymphocyte reaction and the mitogenic response to phytohemagglutinin, suggesting a role for membrane-associated C4 in the afferent phase of immune recognition phenomena.