SB-restricted presentation of influenza and herpes simplex virus antigens to human T-Iymphocyte clones

The HLA-D region of the human major histocompatibiiity complex (MHC) has been shown to be homologous to the murine I region in terms of both structure and function. Both regions encode class II MHC molecules which restrict T-lymphocyte interactions with antigen-presenting cells. We have recently described the MHC restriction and antigen specificities of human T-lymphocyte clones directed at strain A influenza virus 1–3 . The majority of T-lymphocyte clones recognized antigen in the context of cell surface interaction products encoded by HLA-D/DR genes. However, a few clones recognized antigen presented by cells histoincompatible for D/DR antigens. We report here that some of these clones recognize viral antigens in association with antigens encoded by genes identical with or closely linked to the recently described secondary B-cell ( SB ) locus of the MHC 4,5 . This is the first report that SB-restricted antigen recognition may form an integral part of normal, human immune responses.