Prolonged survival of H-2 incompatible skin allografts on F1 animals treated with parental lymphoid cells.

The survival times of -2 incompatible skin allografts were studied in F hybrids treated with parental strain lymphoid cells. The injection of 50×10 A/Sn lymphoid cells into A/Sn×CBA F hybrids greatly prolonged the survival of 5M skin allografts applied 7 days later. Suppression of allograft rejection was observed also in F recipients that were actively or adoptively immunized against the skin graft donor. The immunocompetence of the sensitized F hosts was supressed to a greater degree than that of normal non-sensitized recipients. It is unlikely that immuno-incompetence is caused by basic effects of the graft--host reaction or by antigenic competition since overt signs of a graft--host reaction were not a necessary prerequisite for immunosuppression. It is suggested that a general inhibition of expression of immunity develops as a consequence of the immune reaction, possibly mediated by humoral factors.