Prolonged survival of skin allografts in rats treated with antigen and hydrocortisone and the trend in graft-versus-host reactions.

The mechanism of prolongation of skin allograft survival in rats treated with specific antigen and hydrocortisone was studied in the strain combination with the strong (H-1 + non-H-1) and weak (non-H-1) antigenic difference. The grafts differing from the recipients at the weak non-H-1 loci only showed the longest survival although unresponsiveness to the strong (H-1) antigens of the donor type had already disappeared. In both strain combinations, immunological reactivity of lymphoid cells from treated animals was demonstrated in local GVH reactions at the end of the treatment (i.e., 12 days after transplantation). Lymphoid cells isolated from long surviving (100 days) AVN recipients of non-H-1 different grafts did not react in the GVH test. Attempts to obtain prolongation of skin allograft survival by passive transfer of serum removed after termination of immunization with strong (H-1 + non-H-1) or only weak (non-H-1) antigens were not successful.