**7. Gender**

410 Chronic Kidney Disease

Hence, when identical twins or siblings, who have the same HLA antigens donate to each other, the survival is superior compared to randomly matched cadaveric donors, with an intermediate level of graft survival seen when parents or genetically non-identical siblings donate where one of the haplotypes are matched. In population based programs, which rely predominantly on cadaveric donation, finding single or double haplotype match is obviously not very common. The goal is to find a donor and recipient combination that has zero to minimum mismatches, meaning the least amount of HLA antigens expressed on the surface of donor cells that are not present in the recipient. There has also been recognition of the fact that there are some HLA mismatches that are more significant than others, for example having a DR mismatch is now known to be much more detrimental to graft survival than having a mismatch of the A and B antigens (Coupel et al., 2003; Opelz 1985). In the earlier years of transplantation, having HLA mismatches led to a high incidence of early rejection and eventual graft failure. With the modern and more potent immunosuppressive agents used today, such episodes are rare in the first year. However, despite the immune suppression and the low incidence of AR in the first year, the long term survival of grafts from well matched (6 antigen match or zero mismatch) donors have a longer survival than from those who are not as well matched and according to recent analysis of the national database in the United States (OPTN/SRTR, 2008) this effect is seen in living donors and deceased donors of both extended and non-extended criteria. Despite the above stated evidence pointing towards better survival among well matched organ allocation, only 13% of the organs allocated in the US are well matched. (Takemoto et al., 2000). The main reasons are that despite the large numbers of people on the waiting list, well matched organs are difficult to find. When they are found, the absolute match may be in a different part of the country. If organ allocation is done by HLA only, not considering geographical location, the cold-ischemia time increases as the organ is transported. As the cold-ischemia time increases, chances of delayed graft function increase and overall it negatively affects outcomes and costs. According to an analysis, the added advantage of a

zero mismatch is lost once the cold-ischemia time exceeds 36 hours (Lee et al., 2000).

explained by development of transplant glomerulopathy from CAMR.

Exposure to foreign antigens whether in the form of organ donation, blood transfusion and in the case of women, through child birth, leads to development of antibodies that are reactive towards these antigens, a process referred to as "sensitization". A measure known as the Panel Reactive Antibodies (PRA) estimates the degree of sensitization that a potential recipient has and this reflects the likelihood of having difficulty finding an organ to which the recipient does not have preformed antibodies against. Pre-existing DSA or developing de-novo DSA in the post-transplant period predisposes the recipient to develop AMR. Even if there is no overt episode of AMR clinically, the graft survival is still poor, which is

Strategies to prevent CAN due to HLA incompatibility include matching donors and recipients with minimal mismatches, cross matching to ensure that there is no DSA. If DSA are present, various desensitization protocols utilizing intravenous immunoglobulin and plasmapheresis can be used to decrease the likelihood of AMR. In the post transplant period, a watchful evaluation of kidney function with close monitoring of serum markers as well as urinalysis should be kept to recognize early development of AMR and CAMR. The threshold to evaluate renal dysfunction with kidney biopsy should be low in patients at increased risk of rejection due to HLA incompatibility. In the outset, patients who are likely Due to lack of the Y chromosome in women, antigens coded for by the Y chromosome are recognized as foreign when organ transplantation occurs from a male donor to a female recipient (McGee et al., 2010, 2011). While this does not manifest immunologically as strongly as HLA incompatibility, it does have an effect of having shorter graft survival when an organ is taken from a male donor and transplanted to a female recipient (McGee et al., 2010). This effect is more strongly noted among bone marrow transplants, but is also present to some degree in solid organ transplants such as the kidney (Gratwohl et al., 2008). The decreased survival of male to female donation compared to female to male donation is seen despite the fact that in most instances a higher nephron mass of a male donor kidney is transplanted into a smaller body of a female recipient.
