HLA-D Region Expression on Thyrocytes: Role in Stimulating Autoreactive T Cell Clones

Abstract

Because T helper cells recognize antigens in conjunction with Class II MHC molecules (I region in mouse or HLA-D region in man), these molecules have a key role in the immune system (1). Normally, Class II molecules are present on well defined sets of cells, actively involved in immune induction (antigen presenting cells). MHC Class II molecules are also considered to be the phenotypic expression of the Ir genes, at least for the murine system (2), suggesting that a similar role is played by the D region products of the HLA gene complex in man. Three groups of D region genes have been well defined (HLA-DR, DP and DQ) and there may be more (e.g. DX, DZ, DO). These different D region gene products, have been demonstrated to be the ‘restriction’ elements involved in the recognition of different antigens (3–5). Moreover a given antigen often, though not always, associates with a given Class II region product.