PROLONGATION OF MURINE VASCULARIZED HEART ALLOGRAFT SURVIVAL BY RECIPIENT-SPECIFIC ANTI-MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-II ANTIBODY

Background, Antibodies targeting recipient major histocompatibility co mplex (MHC) class II molecules have been demonstrated to be effective at prolonging allograft survival, However, antigen-presenting cell dep letion would explain this effect and has not been definitively exclude d as the mechanism of action of such antibodies, We have studied an an ti-MHC class II antibody (OX6) proven to be noncytotoxic in the recipi ent strain used. Methods. Antibody was administer-ed the day before, 2 hr before, and the day after grafting. Results. Antibody administrati on on the day before, 2 hr before, and the day after grafting signific antly prolonged vascularized cardiac allograft survival, Importantly, treatment recognizing recipient MHC was effective, whereas a similar r egimen recognizing donor MHC was not. Conclusions. Noncytotoxic recipi ent MHC class II-specific antibodies modify allograft rejection. Possi ble mechanisms for this therapeutic effect are discussed.