Modulation of the immune response to transplantation antigens. V. A comparison of the effects of antilymphocytic serum and enhancing alloantiserum on effector mechanisms of allograft rejection.

Administration of antilymphocytic serum (ALS) or alloantiserum at the time of graft both stimulate enhanced growth of a tumour allograft, but the effect of alloantiserum is weaker and more dependent on dose. Both antisera suppress (or delay) the development of lymphocyte-mediated cytotoxicity, and partly inhibit the development of activated, cytostatic macrophages. Apart from these central or afferent effects, ALS added to an in vitro culture of immune effector cells and EL4 target cells strongly inhibits cytotoxicity, while in this model, alloantiserum is less effective in this respect. The relevance of the effects observed in vitro to in vivo facilitation of allografts is discussed.