Hybrid immune response to parental liver tissue grafts.

Parental-to-F1-hybrid liver tissue grafts in like-sex donor-recipient combinations survive indefinitely, although several F1 recipients demonstrate an immunological response to the parental graft. Female F1 recipients, particularly those carrying the H-2b haplotype, respond vigorously to male parental liver grafts. However F1 female responses to male parental liver tissue grafts differ substantively from the responses of parental females to syngeneic male grafts. C3H male liver grafts are rejected vigorously by F1 females as long as the F1 carries the H-2b haplotype. These findings support previous reports of strong immunological responses to C3H H-Y antigen in female F1 and C3H.SW animals, a response which is absent in C3H females. Female F1 hybrids carrying the H-2b haplotype do not reject grafts of B10 or B6 male liver as rapidly as do B10 or B6 parental females. This reduced F1 response may be related to the formation of hybrid antigens and consequent alteration of the anti-H-Y response. Alternatively, cells that specifically suppress the anti-H-Y response may be present in F1 hybrids. Factors responsible for suppression appear to be controlled by non-MHC antigens, at least in (C3H X B6 or B10)F1 hybrids.