Toxic shock syndrome and bacterial superantigens: An update

Toxic shock syndrome (TSS) is an acute onset illness characterized by fever , rash formation, and hypotension that can lead to multiple organ failure a nd lethal shock, as well as desquamation in patients that recover. The dise ase is caused by bacterial superantigens (SAGs) secreted from Staphylococcu s aureus and group A streptococci. SAGs bypass normal antigen presentation by binding to class II major histocompatibility complex molecules on antige n-presenting cells and to specific variable regions on the beta -chain of t he T-cell antigen receptor. Through this interaction, SAGs activate T cells at orders of magnitude above antigen-specific activation, resulting in mas sive cytokine release that is believed to be responsible for the most sever e features of TSS. This review focuses on clinical and epidemiological aspe cts of TSS, as well as important developments in the genetics, biochemistry , immunology, and structural biology of SAGs. From the evolutionary relatio nships between these important toxins, we propose that there are five disti nct groups of SAGs.