Expression and function of HLA-B27 in lipid-linked form: Implications for cytotoxic T lymphocyte-induced apoptosis signal transduction

Major histocompatibility complex (MHC) class I antigen-restricted cytotoxic T lymphocytes (CTL) kill their target cells not only by inducing irreversible membrane damage but also by triggering a programmed suicide cascade (apoptosis) in target cells. Recent evidence suggests that MHC class I antigens are involved in apoptosis signal transduction in T cells. Therefore, it is possible that MHC class I antigens are also responsible for CTL-induced signal transduction in target cells leading to apoptosis. To test this hypothesis, we have expressed HLA-B27 in Chinese hamster ovary (CHO) cells in a phosphatidyl inositol (PI) anchored form. The expressed Pl-anchored HLA-B27 (PI-B27), a 42-kDa molecule which can be cleaved off the cell surface by Pi-specific phospholipase C, can function as an MHC restriction and antigen presentation element for specific CTL. Furthermore, PI-B27 transfectant CHO cells undergo rapid DNA fragmentation when pulsed with the appropriate peptide and treated with specific CTL, suggesting that the cytoplasmic and transmembrane domains of the heavy chain of class I MHC molecules are not required in CTL-induced apoptosis signal transduction in target cells.