14 September 2016

Gender and Corneal Transplants – How Much Does It Matter?

The debate over the significance of gender, and the extent to which the genders differ, is as old as time itself – but the debate on the science and biology of gender is somewhat more recent. Now, an extensive new study has been conducted which throws up an interesting, scarcely considered factor in this debate – the question of gender’s significance in donor matching in a field close to the Tej Kohli Cornea Institute’s heart – corneal transplants.

The study, which was led by Dr. Stephen Kaye, an ophthalmologist at The Royal Liverpool University Hospital, analysed more than 18,000 U.K patients and discovered that female transplant recipients’ new corneas were more likely to take if the donor’s gender was also female – but that donor gender had no bearing on the success of male transplant recipient’s procedures. The effect was particularly pronounced with certain diseases – for example, if recipients were suffering from the corneal disease Fuchs Endothelial Dystrophy, a disease which affects the regulation of fluid in the cornea, female transplants were 40% less likely to fail if they received a female’s cornea, as opposed to a male’s.

The average rate of failure for gender-matched transplants was found to be 180 for every 1000 transplants, as opposed to 220 for male-to-female transplants , but again, this effect didn’t work both ways. So why are males able to accept transplants of any gender, while females are not? And why hasn’t gender previously been treated as a consideration in corneal transplants?

Professor Kaye, the studies leader, put forward a hypothesis as to the study’s results, stating that “These findings are most likely a result of H-Y antigen incompatibility associated with the male Y chromosome. Females do not have a Y chromosome, so there is no H-Y incompatibility from female donors to male patients”. You can think of this as comparable to someone being an omnivore vs a vegetarian – the omnivore can eat both meat and vegetables without becoming ill, whereas if you give the vegetarian meat, which they are not used to, they have a chance of becoming sick.

As to why gender has not been given consideration in corneal transplants previously – corneal transplants are matched differently in the UK, due to the largely homogenous population – they are often matched by their leukocyte antigen (HLA) status. HLA proteins help the body to identify which cells belong to it and which are foreign, making it a good qualifier for the likelihood of a transplant being rejected. The USA and Australia are more diverse, so HLA matching is seen as redundant – and it has been speculated that the gender effect is only seen in HLA matched pairs.

It seems, therefore, that the gender effect could be considered to be a luxury of choice – where transplant donors are scarce, recipients are unlikely to decline an organ based on an increased chance of that organ being rejected, if the alternative is receiving no transplant at all. However, in the UK, where HLA matching is already carried out, if the study’s findings are confirmed by further research, there could be significant changes to how cornea donors are matched in the future – and if HLA matching is eliminated as a cause of the gender effect, other countries are sure to follow suit. At the TK LV Prasad Institute, we’re committed to giving our patients the very best chance of long-term eye health, and we eagerly anticipate this study being confirmed or contradicted.