Chronic Skin Graft Rejection in the Urodela

Reciprocal first-set skin xenografts between four genera of normal adult urodeles resulted in chronic rejection in six combinations (median survival time, 32–50 days) and subacute rejection in two combinations (median survival time, 19 and 24 days). Several inter-familial xenografts survived indefinitely. This unique rejection reaction is attributed to weak histocompatibility interactions and antigen sharing. Whether these common antigens are exclusively transplantation antigens, species-specific antigens, or tissue-specific antigens remains speculative. Chronic xenograft rejection offers additional evidence of the lack of a major histocompatibility locus in urodele amphibians and suggests that “weak” transplantation alloantigens are also functioning as “weak” antigens in xenogeneic hosts.