title: Streptococcus pyogenes: Insight into the function of the streptococcal superantigens.
abstract: The group A streptococcus produces a number of highly potent exoproteins that act as superantigens. The cascade of pro-inflammatory events that follow invasive streptococcal infection is greatly enhanced by production of such toxins, leading to profound hypotension and multi-organ failure in some cases. Superantigens such as streptococcal mitogenic exotoxin Z (SMEZ) interact with host MHC class II and the T cell receptor, leading to activation events in both cells. In vitro, these interactions lead to expansion and cytokine production by specified T cell subsets. Studies using humanized HLA class II transgenic mice and isogenic streptococcal strains have characterised the in vivo responses to superantigens produced in the context of live infection. Notwithstanding the obvious deleterious role of superantigens in toxic shock, the evolutionary advantage conferred by these toxins remains a subject of speculation.
authors.affiliation: Gram-Positive Molecular Pathogenesis Group, Department of Infectious Diseases, Imperial College London, Hammersmith Hospital, Du Cane Road, London W12 0NN, United Kingdom. s.sriskandan@imperial.ac.uk
authors.forename: Shiranee
authors.initials: S
authors.lastname: Sriskandan
authors.forename: Lee
authors.initials: L
authors.lastname: Faulkner
authors.forename: Philip
authors.initials: P
authors.lastname: Hopkins
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000276:immunology*; D016207:Cytokines / Q000276:immunology; D005098:Exotoxins / Q000276:immunology*; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D008822:Mice, Transgenic; D017434:Protein Structure, Tertiary; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D012772:Shock, Septic / Q000276:immunology*; D013290:Streptococcal Infections / Q000276:immunology*; D013297:Streptococcus pyogenes / Q000276:immunology* / Q000472:pathogenicity; D018089:Superantigens / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000276:immunology
chemical_list: D001427:Bacterial Toxins; D016207:Cytokines; D005098:Exotoxins; D000949:Histocompatibility Antigens Class II; D011948:Receptors, Antigen, T-Cell; D018089:Superantigens; C107894:mitogenic exotoxin Z protein, Streptococcus