Superantigens - powerful modifiers of the immune system

Superantigens are powerful microbial toxins that activate the immune system by binding to class II major histocompatibility complex and T-cell recepto r molecules. They cause a number of diseases characterized by fever and sho ck and are important virulence factors for two human commensal organisms, S taphylococcus aureus and Streptococcus pyogenes, as well as for some viruse s. Their mode of action and variation around the common theme of over-stimu lating T cells, provides a rich insight into the constant battle between mi crobes and the immune system.