Apparent lack of H-2 restriction of allograft rejection.

BALB/c ByJ (H-2d) mice immunized with tail skin grafts of either B10.D2 (H-2d) or B10 (H-2b) demonstrated similar second set rejection of B10.D2 tail skin. This apparent lack of H-2 restriction was not due to the induction of a new population of cytotoxic T lymphocytes (Tc) since 450R given 24 hr before the challenge graft did not abrogate the second set reactivity. Host macrophage processing or anti-Qa-2 reactivity was also not the explanation for the lack of H-2 restriction since immunization of BALB/c Li mice with either B10.D2 or B10 tail skin grafts resulted in second set rejection of B10 tail skin. Shared public H-2 specificities of H-2d and H-2b may result in cross-reactive Tc, thus causing the apparent lack of H-2 restriction. However, no H-2 restriction of allograft rejection is observed when only one public H-2 specificity is shared between the recipient and the allogeneic challenge graft (H-2f and H-2k combination). These results suggest that H-2 restriction of T cell cytotoxicity has little relevance in allograft rejection because 1) one public H-2 specificity is sufficient to cause cross-reactivity or 2) Tc are not the major effectors of allograft rejection.