This patient has toxic shock syndrome due to preformed Staph aureus toxin TSST-1. This toxin binds to the variable beta portion of the T-cell receptor as a superantigen.
Superantigens are microbial molecules that can activate T cells in nonspecific fashion. They bind to certain domains on MHC class II molecules of macrophages and to certain domains on the variable beta chain on the T cell receptor, forming a bridge between the two cells. A superantigen can bind to T-cell receptors from a number of different T cells, as long as they share similar amino acid sequences in the variable portion of the beta-chain.
Bamberger and Boyd review management of S. aureus infections. With regard to toxic shock syndrome, they advise timely removal of the S. aureus source and use of a beta-lactamase–resistant antistaphylococcal antibiotic. Clindamycin, which has the potential of reducing toxin production, is also recommended.
Uchiyama et al. conducted one of the earliest experiments that linked TSST-1 to MHC Class II molecules on T-cells. They attached radioactive markers on TSST-1 and noticed T-cell proliferation via IL-2, but not in other types of immune cells. Via gel electropheresis, they then identified MHC Class II in association with TSST-1.
Illustration A depicts a CD4+ T-cell becoming activated by an antigen presenting cell. Note the antigen:MHC II complex recognition by the T-cell receptor.
Answer 1: CD3 (composed of 2 CD3-epsilon, 1 CD3-delta, and 1 CD3-gamma) is a part of the T-cell receptor complex.
Answers 2 and 3: As described above, CD4 helper T-cells bind to an MHC complex containing MHC class II and to B7 on antigen presenting cells during activation.
Answer 5: As described above, CD4 helper T-cells bind to IL-2 to promote proliferation, not the Fas ligand. The Fas ligand is involved in the apoptosis cascade.
Bamberger DM, Boyd SE. Management of Staphylococcus aureus infections. Am Fam Physician. 2005 Dec 15;72(12):2474-81. Review.
PMID:16370403 (Link to Abstract)
Uchiyama T, Imanishi K, Saito S, Araake M, Yan XJ, Fujikawa H, Igarashi H, Kato H, Obata F, Kashiwagi N, et al. Activation of human T cells by toxic shock syndrome toxin-1: the toxin-binding structures expressed on human lymphoid cells acting as accessory cells are HLA class II molecules. Eur J Immunol. 1989 Oct;19(10):1803-9. PubMed
PMID:2583222 (Link to Abstract)