MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-I MOLECULE SELVES AS A LIGAND FOR PRESENTATION OF THE SUPERANTIGEN STAPHYLOCOCCAL-ENTEROTOXIN-B TO T-CELLS

Superantigens, such as staphylococcal enterotoxin B (SEE), elicit a st rong proliferative response in T cells when presented in the context o f major histocompatibility complex (MHC) class II molecules. We observ ed a similar T-cell response, when MHC class II-negative epidermal cel l lines were employed as antigen-presenting cells, Immunoprecipitation studies indicated that the ligand to which SEE bound had a molecular mass of 46 kDa, Radiolabeled SEE could be immunoprecipitated from isol ated membrane proteins on the SCC13 epidermal cell line with a monoclo nal antibody directed against the MHC class I molecule, and transfecti on of the K-562 cell line with MHC class I molecules showed a 75% incr eased SEE-binding capacity compared with the nontransfected MHC class I- and class II-negative counterpart, In functional studies, antibodie s to the MHC class I molecule inhibited T-cell proliferation by at lea st 50%, From these studies, we conclude that MHC class I molecules on malignant squamous cell carcinomas serve as ligands for SEE, which, gi ven the appropriate costimulatory signals, is sufficient to allow for superantigen-induced T-cell proliferation.