Male and female kidneys are slightly different
Women who get a replacement kidney from a male donor are more likely to reject the new organ, scientists suggest.
Swiss researchers looked at almost 200,000 operations, finding an 8% increase in the chance of failure when male kidneys were given to women.
Writing in The Lancet medical journal, they suggested same-sex transplants should be considered in future.
However, the UK Transplant Authority said its own research had not found any gender difference.
The idea of the "sex" of donor tissue influencing how it is received by the recipient's immune system is not a new one.
In stem-cell transplants, men who get cells from a female are at an increased risk of dangerous "graft-versus-host" disease, and women who get "male" cells are more likely to reject them, or have an immune reaction to molecules specific to males found on the surface of cells.
The researchers from the University Hospital in Basel examined the outcome of a total of 195,516 transplants between 1985 and 2004 at more than 400 hospitals in Europe.
They found that "graft loss" - the rejection of the new organ - was more likely in kidneys from female donors than those from male donors after both a year and 10 years.
The biggest difference was the transplantation of male kidneys into female recipients, where the chances of failure in the first year were 11% higher than average, and 8% more likely overall.
They said that one advantage of "same-sex" transplants was that men would probably benefit from the higher concentrations of "nephrons" - the basic structural unit of the kidney - found in kidneys from men.
Women would profit from the lower risk of rejection on receiving a female donor kidney.
Dr Connie Davis, from the University of Washington in Seattle, said that the effect on the female immune system of male-specific molecules in donor tissue "could no longer be ignored".
She said that the current success rates for donor organ transplantation - and the shortage of suitable organs, meant that policies should not change yet.
"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."
However, a spokesman for UK Transplant said that its own study had found no differences between rejection rates between genders.
He said: "No statistical evidence was found to suggest any of the sex-related factors significantly affected post-transplant graft survival.
"Therefore, donor to recipient sex matching is not something that is considered in the kidney allocation scheme."