A new study suggests that it might be beneficial to gender match corneal transplants, which in turn could increase the rate of success. Researchers have found that there is a lower rate of success if the donor for corneal transplantation is male and the recipient is female.
The researchers looked into the rejection rates of corneal transplants in the UK, taking into account over 18,000 patients. After five years, more than 80 percent of those who had undergone a transplant still had functioning grafts, but a higher proportion of male-to-female transplants had failed. Out of 1,000 operations, on average 180 failed if the gender was matched, while 220 failed if male corneas were given to female patients.
There were also differences depending on what condition the patients had. The researchers found that the gender mismatch was more pronounced if the woman needing the transplant had Fuchs endothelial dystrophy, where they found that a massive 18 percent of male-to-female grafts failed, compared to 12 percent of female to female. Once they adjusted for other factors, the researchers found that female-to-female grafts were 40 percent less likely to fail, and 30 percent less likely to be rejected.
“These findings are most likely a result of H-Y antigen incompatibility associated with the male Y chromosome,” explains Professor Stephen Kaye, author of the paper published in the American Journal of Transplantation. “Females do not have a Y chromosome so there is no H-Y incompatibility from female donors to male patients. This effect, however, is not reciprocated when the roles are reversed, that is, when male donors are transplanted to female recipients.”
The H-Y antigen incompatibility occurs because the H-Y antigen system is produced by a series of seven genes found on the Y chromosome, which only men have. These genes produce proteins with distinct amino acid sequences that are different from their homologues that are produced by the X chromosome found in women. It is thought that when the male tissue is then transplanted into females, the body is exposed to these male antigens and therefore the body mounts an immune response. This effect has not only been seen with corneas, but also other tissues such as bone marrow.
Now that H-Y antigen incompatibility has possibly been identified as an issue for corneal transplants, it should be an easy way to cut rejections. “If confirmed, this would be relatively straightforward to put into place without delay in donor tissue allocation to patients or any significant added cost,” says Professor Kaye. “The long-term impact this could have on patient care may be substantial.”
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