Superantigens and Exotoxins Quiz

Superantigens are ~25 kDa toxins that are extremely potent immune system activators. They are highly soluble, have no enzymatic activity or conformational changes, and generally have little primary sequence homology but highly conserved structure. They can lead to high-level production of IL-2, IL-17A, and IFNγ from T cells, as well as other cytokines, triggering a cytokine storm which can develop into toxin shock syndrome.

The primary cause of staphylococcal toxic shock syndrome is TSST-1 (menstrual form) and TSST-1, SEB, or SEC (nonmenstrual forms), while streptococcal toxic shock syndrome is primarily caused by SpeA and SpeC, occurring in association with severe invasive disease.

Staphylococcal TSS symptoms include fever, hypotension, rash, and desquamation caused by toxic shock syndrome toxin-1 (TSST-1) and staphylococcal enterotoxins (SEs). Streptococcal TSS symptoms include fever, hypotension, rash (not always), and desquamation (not always), commonly associated with invasive disease caused by streptococcal pyrogenic exotoxins (SPEs).

Conventional T cell activation involves T cell receptor (TCR) recognition of antigen presented by MHC II on an antigen-presenting cell, while T cell superantigen-mediated activation bypasses the antigen and MHC II recognition, directly activating a large proportion of T cells.

Superantigen-induced immune system activation leads to high-level production of IL-2, IL-17A, and IFNγ from T cells, as well as other cytokines, including TNFα from macrophages. This can develop into a cytokine storm, triggering toxic shock syndrome.