Gender Key in Kidney Transplant Outcomes: Study

Female patients who receive male kidney in transplant are more likely to reject the donor organ, compared to the other three donor-recipient combinations, a new Swiss study unfolds. Highlighting the sex-issue in organ transplant cases, sex-matching for kidney donors and recipients should be taken into consideration to reap better outcomes, researchers suggest.

Starting from 1985, the researchers at the University Hospital Basel examined the outcomes of little less than 2,00,000 kidney transplants conducted at over 400 centers in Europe till 2004 end.

Organ rejection or ‘graft-loss’, was more likely in female recipients who received male organ, both after a year and 10 years, the results reveal. Compared to other three donor-recipient combinations, an 8 percent increased risk of graft failure was reported among female recipients, while an 11 percent increased risk of graft failure-related death in the first year was noted. These risks dropped to 6 percent and 10 percent, respectively, between years 2 and 10, researchers added.

"Our multi-variable analysis showed that transplantation of kidneys from male donor into female recipients caused an increased rate of graft failure, which suggests an immunological H-Y effect in renal transplantation during the first year after transplantation that extends to 10 years of follow-up ... Consideration of sex should be integrated into future prospective analyses and decisions on organ allocation," the researchers report in this week's issue of ‘The Lancet’.

As the number of nephrons- the basic structural and functional unit of the kidney - vary in both male and female organs, male recipients are more likely to benefit from bigger male kidneys. Contrary, as women themselves have fewer nephrons than men, they do not need the same number of nephrons as men, and thus are more likely to reject male organs, the researchers explained.

The H-Y antigens know to cause disruptive results in male-female stem-cell transplants are also believed to affect kidney patients. "H-Y antigens can no longer be ignored in the setting of solid-organ transplantation. A lot of work still needs to be done on the actual antigens and the immunological responses that might be associated with rejection. However, the science is still too premature to suggest that allocation schemes from dead donors or selection of living donors for transplantation take notice of this effect, in view of the good long-term success with sex-mismatched allografts and the limited access to organs," Dr Connie L Davis wrote in an accompanying comment.