Analysis of Superantigen Binding to Soluble T-Cell Receptors

The T-cell receptor (TCR) is a membrane-bound, multi-subunit complex that plays a key role in antigen recognition of cell-mediated immunity. The α and β chains of the TCR are extracellular domains that are the primary contact regions for two types of antigens. In conventional T-cell recognition, the αβ TCR binds to an intracellularly-processed peptide antigen in the context of a major histocompatibility complex (pMHC) on the surface of an antigen-presenting cell (APC), providing for the specificity of an immune response. However, superantigens (SAgs) are unprocessed proteins that circumvent this normal antigen presentation by crosslinking the TCR with a class II pMHC, leading to a nonspecific, polyclonal expansion of T cells (1 ).