Recognition of H-2 domains by cytotoxic T lymphocytes

The polymorphic major histocompatiblity antigens (H-2) have a crucial role in the activation of antigen-specific T lymphocytes. Thus, H-2 antigens are not only recognized by allogeneic lymphocytes leading to generation of cytotoxic T lymphocytes (CTLs), but it has also been demonstrated that in syngeneic systems most T cells are only able to recognize foreign antigens in conjunction with their own MHC (major histocompatibility complex) antigens. This phenomenon, termed H-2 restriction¹, may be the key to our understanding of the biological function of MHC antigens. It is not clear whether recognition by T cells of H-2 on a molecular level is confined to particular domains on the H-2 molecule, nor whether the same polymorphic H-2 sites, which are characterized by antibodies, are recognized by allogeneic as well as by H-2-restricted syngeneic CTLs. Previous findings² indicate the existence of at least two major polymorphic domains on the H-2K^k molecule as defined by antibodies. Here we show the existence of CTLs with specifity for these polymorphic domains, and the preferential recognition of a particular domain by both alloreactive as well as H-2-restricted CTLs.