The H–Y Transplantation Antigen: A Y-linked or Sex-influenced Factor?

Abstract

IN mice and rats there is one exception to the rule that grafts are always accepted between members of an isogenic population. This applies when females are challenged with skin and other tissues from male donors^1–6. The ability of females to reject these grafts varies from strain to strain. For example, while virtually 100 per cent of C57BL/6 (hereafter C57) females and about 75 per cent of A strain females reject male skin isografts, CBA and AU strain females usually accept such grafts. This interstrain diversity occurs despite the fact that the specificity of the Y antigen or “Y factor” is apparently the same in male mice of all stocks⁷. The basis for this variability stems from two factors: the first is the genotype of the female which determines her capacity to react against male skin and the second is the genetic background of the male which influences the expression of the Y antigen⁸. Thus the complete penetrance of the Y factor in C57 mice is due to the females of this strain being relatively strong reactors against male skin isografts, and is not because the antigen is strongest in this strain. Indeed, that the antigen is weaker in C57 males than in CBA males follows from the fact that (CBA × C57)F₁ hybrid females reject grafts from CBA males more frequently than from C57 males⁸.