Anti·red cell activity of lymphocytotoxic antibodies: and in vitro and in vivo evaluation

The need to obtain non-toxic antilymphocyre sera (ALS) led to the in vitro and in vivo evaluarion of its crossreactivity for red cells. The findings showed thar the antibodies coating the erythrocytes in vitro are idenrical with the antibodies that sensitize lymphocytes by the cytotoxicity rest. It would appear that rhe observed similarities are related to sharing of antigenic determinants by both the lymphocytes and red cells. High concentrations of lymphocytotoxic antibodies can be anticipated to sensitize and affect the biological function of many other tissues besides the red cells. Intensive immunizarion schedules were found to produce immune complexes (lymphocyte-antilymphocyte factors) which in turn induced lymphocytosis in place of the anticipated lymphopenia. Absorption of the immune complex as well as the red cell antibody significantly reduced the toxic properries of ALS but did not improve its immunosuppressive acrivity. The short-term exposure of baboons to toxic preparations of baboon ALG was observed to lower their serum complement value. The most likely explanation for this associated activity appears to be complement utilization by avid in vivo antigen-antibody inreracrion. It is believed rhat the synthesis of antibodies to intact lymphoid rissue represents a srimulus ro multiple antigen determinants. The need to investigate the effectiveness of antibody production to subcellular components of the lymphocyte is indicated before the biological approach to immunosuppressive therapy can be accepted as a safe procedure for man