It is located in the short arm 6P2 1.3 1 region of chromosome 6, with a length of 3600KB. According to the difference of function and product structure, it can be divided into three categories: classical HLA genes, immune function-related genes and immune independent genes. Classical HLA genes are closely related to acute rejection of blood transfusion and transplantation. Therefore, it is of great clinical significance to classify the classical HLA genes.

Human diseases are closely related to genes. With the development of medicine, leukemia, thalassemia, renal failure and so on. Can be detected by the latest genetic technology, and then find a suitable donor for transplantation.

HLA*** can be divided into four types: Type I molecules, including HLA-A, HLA-B and HLA-C, are widely found in various tissues and cells;

Type II molecules, including HLA-DP, HLA-DQ and HLA-DR, exist in B cells, macrophages and activated T cells.

Type III molecule is a complement system, including C2 and C4 sites, which exists in serum.

Type ⅳ molecules may be some differentiation antigens, which only exist in lymphocytes, some cytotoxic T cells and white blood cells.