The effects of allelic dosage and graft size on skin graft survival across a weak histocompatibility barrier.

Normal skin was grafted between congenic strains of mice to test the effect of allelic dosage at the weak -1 locus. Heterozygous grafts survived longer than homozygous grafts when placed on different A hosts. The same difference was noted when both grafts were put on opposite sides of the same A host. Both allelic types gave a direct relationship between graft size and survival time over a wide size range, but the slope of the heterozygous dose—response curve was much steeper, with some of the large grafts surviving permanently. Grafts in the combination male to male survived longer than those in the combination female to female. The results are discussed in terms of a possible distinction between antigen available for the afferent and efferent immunological pathways.