Human leukocyte antigens (HLA) are transmembrane protein molecules encoded by genes of the major histocompatibility complex (MHC) and play a key role in antigen presentation and the regulation of the immune response. Class I HLA molecules mediate the presentation of endogenous antigens to CD8+ T-lymphocytes, whilst class II molecules are responsible for presenting exogenous antigens to CD4+ T-lymphocytes. Thus, the HLA system is a central element in the mechanisms of ‘self’ and ‘non-self’ recognition in the human body.
The high degree of polymorphism in HLA genes results in significant individual variability in the immune response and is of critical importance in transplant medicine. HLA incompatibility between the donor and recipient is one of the key risk factors for the development of immunological graft rejection. Consequently, the accurate determination of the HLA profile is an essential stage of laboratory testing when selecting donors for organ and haematopoietic stem cell transplantation.
In modern laboratory practice, HLA typing is carried out using molecular genetic methods, in particular PCR-SSP, SSO (on the Luminex platform) and NGS, which provide varying levels of resolution — from low to high. The choice of method depends on the clinical objective: ranging from screening tests to high-precision allele typing required for haematopoietic stem cell transplantation.