The success of a kidney transplant may depend on gender. Researchers at University Hospital Bazel analyzed data on data on 195,516 people in Europe who received kidneys from deceased donors between 1985 and 2004 and concluded that gender should be considered when choosing a donor.

Transplantation of kidneys from male donors into female recipients was associated with an 8 percent risk of graft failure and an 11 percent increased risk of graft failure-related death in the first year, “which suggests an immunological H-Y effect in renal transplantation during the first year after transplantation that extends to 10 years of follow up,” researchers said. It appears that woman have an immune reaction to molecules specific to males.

“Consideration of sex should be integrated into future prospective analyses and decisions on organ allocation,” researchers wrote, according to the Washington Post.

Male recipients may benefit from male kidneys that have higher concentrations of “nephrons” (the basic structural and functional unit of the kidneys). Women may not need the same number of nephrons as men, and could benefit from female donor kidneys.

University Hospital of Basel researchers concluded that “same-sex” transplants should be considered when choosing donor matches. They added that “a lot of work still needs to be done on the actual antigens and the immunological responses that might be associated with rejection.”