Inhibition of human lymphocyte proliferation by monoclonal antibody to transferrin receptor

A monoclonal antibody, 42/6, which blocks the binding of transferrin to its receptor on the cell membrane, inhibits proliferation of human lymphocytes stimulated by phytohemagglutinin. Anti-receptor antibody B3/25, which does not block transferrin binding, does not alter the mitogenic response. Addition of soluble iron, in the form of ferric nitrilotriacetic acid, results in partial reversal of inhibition. Lymphocytes in the quiescent phase of the cell cycle at the time of 42/6 antibody addition are unable to traverse S phase, whereas cells actively proliferating when antibody is added are sensitive to its inhibitory effects throughout all phases of the cell cycle. Inhibition is static rather than cidal, since it can be reversed by removal of antibody after up to 48 hr of exposure.