Human leukocyte antigen and its role in transplantation biology

Human leukocyte antigens (HLA), the human version of the major histocompatibility complex (MHC), an integral part of maintenance of immune surveillance, have been widely studied for their roles in transplantation biology. A donor with an identical HLA system can donate tissue more successfully than the one who is not matched. The MHC is divided into class I, II, and III antigens; class I and II play important roles in transplantation immunology. HLA is codominantly expressed on chromosome 6 in every individual; HLA-A, -B, and -DR is known as the "haplo-type." There are two sets of HLA antigens in each individual. Thus a child can inherit four different haplo-type combinations from parents. There is a 25% chance of totally matched or mismatched siblings and a 50% chance of half-matched siblings among a family with parents being a 50% match. The main purpose of HLA typing and lymphocyte crossmatching (LCM) in transplantation is to assess donor-recipient immune compatibility and identify the presence of preformed donor-specific cytotoxic alloantibodies in the recipient. It can be tested by serology or molecular techniques. We studied 8462 individuals for HLA typing by serology supplemented with molecular techniques (sequence-specific primers with low resolution). The common alleles were HLA-A19 (9.4%), -A1 (7.7%), -A2 (7.2%), -B5 (10.2%), -B35 (6.6%), -B40 (5.3%), -DR2 (10.2%), -DR5 (7.5%), and -DR7 (5.1%). HLA typing and LCM testing support successful transplantation.