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 via their alpha domain, in particular TRAV27. In turn, this ternary complex activates a large number of T-lymphocytes initiating a systemic release of pro-inflammatory cytokines. Causes also the intoxication staphylococcal food poisoning syndrome. The illness characterized by high fever, hypotension, diarrhea, shock, and in some cases death. Binds 1 zinc ion per subunit. The zinc ion is necessary for interaction with host MHC class II molecules. Interacts with host MHC class II molecules composed of alpha/HLA-DRA and beta/HLA-DRB1 chains. Interacts with host TCR alpha-chain TRAV27. Belongs to the staphylococcal/streptococcal toxin family.