The HLA (human leucocyte antigen) system encodes the major histocompatibility complex (MHC) proteins in humans, is closely related to the body's immune system. The HLA gene complex is located on a 3.6 Mb region within chromosome 6p21. They are the most polymorphic gene family found in the human genome, with more than 10,000 different HLA alleles reported to date, thus the capacity to mount an immune response can be remarkably different between individuals within a cohort selected from a single population.
HLA genes have been strongly implicated in transplant rejection, autoimmune disease, vaccine pharmacogenomics, cancer and infectious diseases. HLA genotyping is the identification of the HLA class I and class II gene polymorphisms for individuals, which is indispensable for transplant matching and disease association studies.