Gratwohl A et al. (2008) H-Y as a minor histocompatibility antigen in kidney transplantation: a retrospective cohort study. Lancet 372: 49–53

The male-specific minor histocompatibility antigen H-Y is well known to affect the success of hematopoietic stem-cell transplantation; therefore, the sex of the donor and recipient is routinely taken into account in pretransplantation risk assessments. Since H-Y is expressed in all tissues, this antigen would also be expected to have a role in graft rejection after renal transplantation. Registry analyses have shown, however, that the survival of kidneys from male donors is not reduced in female recipients.

To further investigate this issue, Gratwohl and colleagues retrospectively reviewed data from 158,652 adults in 45 countries who had undergone deceased-donor kidney-only transplantation during 1985–2004 (mean follow-up 5.6 ± 4.8 years). According to univariate analysis of the four possible donor–recipient sex combinations, transplantation of kidneys from female donors into male recipients was associated with the poorest graft survival. However, on multivariate analysis, the risk of graft failure was highest for male kidneys in female recipients; hazard ratios in this group were 1.08 (95% CI 1.03–1.14; P = 0.003) for graft loss during the first year after transplantation and 1.06 (95% CI 1.01–1.10; P = 0.008) for graft loss during the subsequent 9 years.

These data indicate that donor and recipient sex should be taken into account during allocation of donor kidneys. The authors suggest that a compensatory effect of a higher nephron dose in male kidneys might explain why univariate analyses apparently fail to show that male donor kidneys fare worse in female recipients.