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, waves of cellular activation, cytokine production, and migration into the lung tissue and airways occur via alphabeta T-cells. Causes also the intoxication staphylococcal food poisoning syndrome. The illness is characterized by high fever, hypotension, diarrhea, shock, and in some cases death. Binds 1 zinc ion per subunit. The zinc ion is necessary for the toxin interaction with MHC class II. Monomer. Interacts with MHC class II molecules alpha/HLA-DRB1 and beta/HLA-DRA chains. The interaction with MHC-II molecules occurs at both zinc-dependent and zinc-independent sites. Interacts with T-cell receptor beta variable 7-9/TRBV7-9. Belongs to the staphylococcal/streptococcal toxin family.