HLA-A2 is most common in Northern Asia and North America populations. MHC class I antigens associated with β2-microglobulin are expressed by all human nucleated cells. MHC class I molecules are involved in presentation of antigens to CD8+ T cells, playing an important role in cell-mediated immune responses and tumor surveillance.HLA-B belongs to the HLA class I heavy chain paralogues. HLA-B7 is a serotype of HLA-B and one of the common HLA types. MHC class I heavy chains associate with β2-microglobulin and are expressed on nearly all nucleated cells. MHC class I molecules are involved in the presentation of of antigens to CD8+ T cells and thereby play an important role in cell-mediated immune responses and immune surveillance.