BINARY AND TERNARY COMPLEXES BETWEEN T-CELL RECEPTOR, CLASS-II MHC AND SUPERANTIGEN IN-VITRO

SUPERANTIGENS are proteins that in association with class II major his tocompatibility complex (MHC)-bearing cells can stimulate virtually al l T cells that express particular classes of the variable beta-domains of the T-cell receptor (TCR)(1). This mechanism of T-cell activation circumvents the usual requirement for peptide-specific MHC recognition . Staphylococcus aureus enterotoxin B (SEB) is a bacterial superantige n that causes food poisoning and shock(2-5). We have characterized the tertiary complex of SEB, a soluble T-cell receptor, and a soluble cla ss II MHC molecule DR1, and the three binary complexes TCR-SEB, SEB-DR 1, and the peptide-specific complex DR1-TCR. We report here that in ea ch case the specificity of the interaction among the soluble molecules is the same as observed in biological assays. Native gel electrophore sis and plasmon resonance affinity measurements indicate that SEB-TCR complex can form in the absence of class II MHC and that SEB-TCR inter action increases the binding of DR1. The observation that a superantig en can form complexes with TCR in both the absence and presence of cla ss II MHC may provide a mechanism for its ability to induce anergy in some circumstances and activation in others(6,7) (reviewed in ref. 8).