Abstract
Phytohemagglutinin-P (PHA-P) given intraperitoneally effectively suppressed the rejection of skin allografts across the H-2 locus in mice. The administration of one large dose of PHA prior to grafting followed by small daily injections after grafting resulted in a 70% increase in graft survival in the C3H to C57 system and a 130% increase in the F1-hybrid to C57 system. This immunosuppressive effect was not accompanied by any mortality or apparent toxicity of PHA. Studies of the peripheral blood suggest that the suppressive activity of PHA in vivo is not dependent on a lymphopenic effect. PHA thus appears to be comparable to antilyphocytic serum in its effectiveness in suppressing allograft rejection without a direct correlation with lymphopenia and with no deaths in the treated animals. These observations lead to the speculation that combined ALS-PHA therapy may be desirable in preventing allograft rejection in the clinical situation.
