Human histocompatibility proteins

Transplantation antigens (later called histocompatibility proteins) were named by Peter Gorer in the 1930s. After 4 decades of immunological work emphasizing their importance in immunobiology, structural work on these proteins began about 1970. During the first decade, HLA proteins were isolated and then separated into two groups. Biochemical studies established the close structural relationships of these groups (now called class I and class II MHC proteins). These structures both contained four domains, although the domains were linked differently. Two of these domains were immunoglobulin-like. They were the first proteins (aside from immunoglobulins) identified as members of the immunoglobulin superfamily of proteins. The crystallization of these proteins in the second decade led to elucidation of the structures of class I and class II MHC proteins, which has changed the way we think about immunology. These molecules each present peptides (8-9mers in the case of class I and 13-14mers in the case of class II) to initiate the immune response.