H-Y antigen

H-Y antigen and homosexuality in men.

J Theor Biol. 1997 Apr 7;185(3):373-8.

Blanchard R, Klassen P.

In men, sexual orientation correlates with the number of older brothers, each additional older brother increasing the odds of homosexuality by approximately 33%. It is hypothesized that this fraternal birth order effect reflects the progressive immunization of some mothers to Y-linked minor histocompatibility antigens (H-Y antigen) by each succeeding male fetus, and the concomitantly increasing effects of H-Y antibodies on the sexual differentiation of the brain in each succeeding male fetus. This hypothesis is consistent with a variety of evidence, including the apparent irrelevance of older sisters to the sexual orientation of later-born males, the probable involvement of H-Y antigen in the development of sex-typical traits, and the detrimental effects of immunization of female mice to H-Y antigen on the reproductive performance of subsequent male offspring.

Department of Psychiatry, University of Toronto, Ontario, Canada. blanchardr@cs.clarke-inst.on.ca


Immune complexes containing H-Y antigen and maternal IgG in cord serum.

Clin Exp Immunol. 1982 Nov;50(2):450-3.

Farber CM, Wachtel SS, Cunningham-Rundles C.

Increased levels of immune complexes are more frequently detected in the serum of newborn males than they are in the serum of newborn females. In one survey of 545 newborns, 21 of 26 (81%) of the babies with high levels of immune complexes in cord serum were boys (Farber, Cambiaso & Masson, 1981). To evaluate the hypothesis that this was due in some cases to the synthesis by the mother of antibodies directed against the 'male-specific' H-Y antigen, we tested for presence of IgG antibodies bound to H-Y antigen in serum samples from 263 newborns including 124 girls and 139 boys. Sera from five of the 10 male newborns with high levels of immune complexes contained IgG bound to H-Y; none of the sera from newborn girls had detectable amounts of those immune complexes; and sera from women who had borne males manifested higher levels of IgG reactive with sources of soluble H-Y than sera from women who had borne females.