Synergistic interaction of H-Y and H-2K in elicitation of graft-versus-host response

Lymph node cells from female bm-1 donors induced greater mortality among male than female (bm-1 X b)F1 hosts which had previously been sublethally irradiated. The same effect was not seen when wild type (b) parental donor cells were injected, nor in other combinations involving H-2K mutant C57BL/6 mice. The selective mortality encountered among male hosts in receipt of bm-1 female cells was shown to depend upon recognition of H-Y in the recipient, because this sex effect disappeared if the donors were first rendered tolerant of H-Y. However, absence of graft-versus-host (GVH) mortality with other combinations indicated that recognition of H-Y alone was not sufficient. When cells from donors tolerant of H-Y were mixed with cells from donors tolerant of H-2Kb, enhanced mortality among male F1 hosts was again observed. We interpret the results to indicate that there is a synergistic interaction of donor lymphocytes which recognize H-Y and H-2Kb during the GVH response.