The gender of donor and recipient plays a larger role in kidney
transplants than previously assumed. Female donor kidneys do not
function as well in men – due to their smaller size. Women have a
higher risk of rejecting a male donor kidney. Therefore, in the future,
gender should be considered more in the allocation of donor kidneys,
say researchers from Basel and Heidelberg.
These results are based on an analysis of the “Collaborative
Transplant Study”, the world’s largest database with long-term results
of organ transplants under the leadership of Professor Dr. Gerhard
Opelz, Medical Director of the Department of Transplantation Immunology
at the Institute of Immunology of Heidelberg University Hospital.
Researchers Professor Dr. Alois Gratwohl, Basel University Hospital,
and Professor Opelz published their analysis in the medical journal The
Data from almost 200,000 kidney recipients analyzed
The researchers analyzed data from almost 200,000 organ recipients
who received a kidney transplant between 1985 and 2004. Overall,
transplanting a female kidney was less successful than a male kidney.
This is attributed to the fact that due to their smaller size, female
kidneys have fewer nephrons – the active components of the kidneys that
Immunological rejection problems occurred most frequently when women
received a male kidney – for them, the risk that the organ would be
rejected was eleven percent higher in the first year after the
operation than for other donor-recipient combinations. And even two to
ten years after the operation, the risk of rejection was still 10
percent higher than for other groups.
Y chromosome likely responsible for rejection
"The higher rate of rejection is most likely caused by the
gender-specific Y chromosome in men,” explains Professor Opelz. In the
future, gender should be one of the factors considered when making a
decision on assigning an organ to a patient.
However, the higher risk of rejection in women is partially
compensated by the effect of more nephrons in a male kidney, so that on
average, female recipients of male kidneys do not have significantly
poorer overall results.
Should kidneys be allocated based on gender in the future?
The allocation of organs for German patients is organized – in
coordination with five other European states – by the computer of the
organ distribution center Eurotransplant. Donor kidneys are assigned
according to criteria (waiting time, compatibility, etc.) set by the
commission for organ transplants of the German Medical Association. The
computer program was also developed by the immunologists from
Immune functions associated with the Y chromosome and which can lead
to rejection of the organ need to be studied more closely in the
future, emphasizes Connie L. Davis, kidney expert at the University of
Washington in Seattle (USA) in an editorial in “The Lancet”. However, a
recommendation to transplant only same-sex organs is not yet
appropriate, because long-term success is good even if the donor and
recipient are of the opposite sex, says Davis.
Journal reference:Gratwohl et al. H-Y as a minor histocompatibility antigen in kidney transplantation: a retrospective cohort study. The Lancet, 2008; 372 (9632): 49 DOI: 10.1016/S0140-6736(08)60992-7