Xenogeneic skin graft rejection is especially dependent on CD4+ T cells

B6 mice were treated in vivo with anti-CD4, anti-CD8, or both anti-T cell antibodies together in an effort to prolong xenogeneic compared with allogeneic skin graft survival. Mice treated with anti-CD4 antibody showed prolonged survival of xenogeneic monkey or rabbit skin even after they had rejected whole MHC-disparate allogeneic mouse skin. Furthermore, the addition of cyclosporine was synergistic with the anti- CD4 antibody in prolonging graft survival. These results suggest that the cell-mediated response to xenogeneic antigens is especially dependent on CD4+ lymphocytes, a feature shared by the response to allogeneic minor histocompatibility antigens. In addition, the results suggest a possible approach to clinical immunosuppression for some forms of xenogeneic transplantation.