Staphylococcal enterotoxin that activates the host immune system by binding as unprocessed molecules to major histocompatibility (MHC) complex class II and T-cell receptor (TCR) molecules. In turn, this ternary complex activates a large number of T-lymphocytes initiating a systemic release of pro-inflammatory cytokines (PubMed:10229190, PubMed:28849041). Causes also the intoxication staphylococcal food poisoning syndrome (By similarity). Interacts with MHC class II molecules composed of alpha/HLA-DRA and beta/HLA-DRB1 chains (PubMed:10229190). Interacts with host T-cell receptor/TCR beta variable chain TRBV8-2 (PubMed:10229190, PubMed:20836565). Belongs to the staphylococcal/streptococcal toxin family.