Final answer:
Superantigens are a class of exotoxins that cause an overactive immune response by inducing a cytokine storm, which can lead to conditions like toxic shock syndrome. The toxic shock syndrome toxin produced by Staphylococcus aureus is an example of such a superantigen. Superantigens nonspecifically activate T cells by binding directly to MHC II and TCRs, bypassing the normal antigen processing pathway.
Step-by-step explanation:
Superantigens are a class of exotoxins that cause excessive and nonspecific stimulation of immune cells, leading to a massive cytokine release, also known as a cytokine storm. This can trigger severe immune responses, which in certain cases can be fatal. For example, the toxic shock syndrome toxin (TSST) produced by Staphylococcus aureus is a well-known superantigen that can lead to toxic shock syndrome. This condition typically arises from vaginal colonization by toxin-producing S. aureus in menstruating women, although it can also occur from colonization at other body sites. When a superantigen binds to Major Histocompatibility Complex (MHC) class II molecules on antigen-presenting cells and T-cell receptors (TCRs) on T cells, it leads to the unregulated, nonspecific activation of T cells. This results in the vast overproduction of cytokines, and consequently, excessive inflammation and immune responses.
Superantigens differ from other antigens as they do not require the usual antigen processing and specificity to T-cell receptors, meaning a single super antigen can activate a large population of T cells, escalating the immune response to a dangerous level.