THE IMMUNOSUPPRESSIVE EFFECT OF MONOCLONAL ANTI-LYT-1.1 ANTIBODIES INVIVO

Monoclonal anti-Lyt-1.1 alloantibody was produced as tissue culture supernatant and administered to mice. The antibody, given i.p., resulted in the suppression of all T cell functions studied, but was without direct effect on B cells. Thus, skin and tumor allograft survival was prolonged and there was suppression of the delayed-type hypersensitivity response; T cell help in the anti-sheep red blood cell antibody response, responder cells in the mixed lymphocyte reaction (MLR), leukoagglutinin-responsive cells, cytotoxic T cell (Tc) function and the induction of Tc were either totally or partially suppressed, all these responses being mediated by Lyt-1+2- or Lyt-1+2+ cells in CBA/H mice. There was no inhibitory effect on the MLR-stimulating or lipopolysaccharide-responsive cells. The administration of the anti-Lyt-1.1 antibody was accompanied by a depletion of Lyt-1.1+ T cells from both spleen and lymph node. Thus, the monoclonal anti-Lyt-1.1 antibody apparently is active in vivo with a selective effect on T cells. The results also have important implications for studies of T cell interactions in the mouse in vivo and for similar studies in man.