This is an efficient mechanism for destroying virally infected cells. It may be that the extensive range of HLA antigens is required to provide a sufficiently diverse population of essential immune recognition markers to protect a species from new epidemics, and could also represent a defence against potential mimicry of infectious agents. It is the role of HLA in discriminating between self and non-self that makes it important in transplantation. This was first described in 1966 by van Rood. Patients for the renal transplant list are tissue typed after assessment for suitability.
Donors are tissue typed after their organs have been harvested.
Donor and recipient should be ABO blood group compatable. Graft survival has been shown to be significantly raised in patients with a zero mismatch at the A, B, and DR loci. The relatively small size of waiting lists within each transplant unit, and the polymorphism of the HLA system means that there is little chance of a cadaveric donor fully matching a recipient. Beneficial matching allows one mismatch at either the A or B locus, with only slight reduction in graft survival. The variation in HLA antigen frequency between different ethnic groups has a marked effect on tissue matching.