ABSTRACT
The HLA class I antigens (-A, -B, and -C) are expressed on all nucleated cells and are recognized by CD8+ T cells. However, the HLA class II antigens (-DR, -DQ, and -DP) have a selected tissue distribution, are expressed on the cell surface of the antigen presenting cells, and are recognized by CD4+ T cells. The HLA class II antigens may also be expressed on a variety of nonimmune cell types on stimulation with IFN-γ. Each individual inherits six or seven HLA antigens (three class I and three or four class II) from each parent. All such antigens are codominantly expressed on the cell surface. The entire set of HLA-A, -B, -C, -DR(-DR51/52/53), -DQ, and -DP antigens encoded on chromosome 6 is called a haplotype.
