superantigens

Superantigens are a class of potent exotoxins produced by certain bacteria that cause non-specific activation of T cells, leading to polyclonal T cell activation and a massive cytokine release.

Mechanism-wise, superantigens bind simultaneously to MHC class II molecules on antigen-presenting cells and to the Vβ region of the T-cell receptor outside the normal peptide-binding groove. This bypasses conventional antigen processing and specificity, resulting in the activation of a large fraction of T cells (not limited by a specific antigen) and the production of cytokines such as IL-2, IFN-γ, TNF-α, and IL-1. The ensuing cytokine storm can drive fever, hypotension, and systemic inflammation.

Most well-known superantigens are produced by Staphylococcus aureus and Streptococcus pyogenes. Examples include the Staphylococcal enterotoxins (SEA, SEB, SEC, SED, SEE) and toxic shock syndrome toxin-1 (TSST-1). These toxins are associated with distinct clinical syndromes, including food poisoning from some enterotoxins and tampon-associated or non-menstrual toxic shock syndrome from TSST-1.

Clinical relevance centers on toxic shock syndrome, characterized by fever, hypotension, rash, and potential multi-organ failure. Management is primarily supportive, with antimicrobial therapy when infection is present; antibiotics can sometimes augment toxin release, so treatment choices may vary by clinical context. Diagnosis relies on clinical criteria supported by laboratory detection of toxin activity or presence. Researchers study superantigens both to understand immune dysregulation and to explore potential therapeutic applications, though their pathogenic potential remains a major concern in infectious disease.