title: Protection against lethal toxic shock by targeted disruption of the CD28 gene.
abstract: Toxic shock syndrome (TSS) is a multi system disorder resulting from superantigen-mediated cytokine production. Nearly 90% of the clinical cases of TSS arise due to an exotoxin, toxic shock syndrome toxin-1 (TSST-1), elaborated by toxigenic strains of Staphylococcus aureus. It is clearly established that besides antigen-specific signals a variety of costimulatory signals are required for full T cell activation. However, the nature and potential redundancy of costimulatory signals are incompletely understood, particularly with regards to superantigen-mediated T cell activation in vivo. Here we report that CD28-deficient mice (CD28-/-) are completely resistant to TSST-1-induced lethal TSS while CD28 (+/-) littermate mice were partially resistant to TSST-1. The mechanism for the resistance of the CD28 (-/-) mice was a complete abrogation of TNF-alpha accumulation in the serum and a nearly complete (90%) impairment of IFN-gamma secretion in response to TSST-1 injection. In contrast, the serum level of IL-2 was only moderately influenced by the variation of CD28 expression. CD28 (-/-) mice retained sensitivity to TNF-alpha as demonstrated by equivalent lethality after cytokine injection. These findings establish an essential requirement for CD28 costimulatory signals in TSST-1-induced TSS. The hierarchy of TSST-1 resistance among CD28 wild-type (CD28+/+), CD28 heterozygous (CD28+/-), and CD28-/- mice suggests a gene-dose effect, implying that the levels of T cell surface CD28 expression critically regulate superantigen-mediated costimulation. Finally, as these results demonstrate the primary and non-redundant role of CD28 receptors in the initiation of the in vivo cytokine cascade, they suggest therapeutic approaches for superantigen-mediated immunopathology.
authors.affiliation: Naval Medical Research Institute, Bethesda, Maryland 20889, USA.
authors.forename: B
authors.initials: B
authors.lastname: Saha
authors.forename: D M
authors.initials: DM
authors.lastname: Harlan
authors.forename: K P
authors.initials: KP
authors.lastname: Lee
authors.forename: C H
authors.initials: CH
authors.lastname: June
authors.forename: R
authors.initials: R
authors.lastname: Abe
mesh_terms: D000818:Animals; D001427:Bacterial Toxins; D018106:CD28 Antigens / Q000235:genetics*; D003433:Crosses, Genetic; D004768:Enterotoxins / Q000276:immunology; D005260:Female; D006579:Heterozygote; D007113:Immunity, Innate / Q000235:genetics; D007371:Interferon-gamma / Q000096:biosynthesis / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D012772:Shock, Septic / Q000235:genetics / Q000276:immunology* / Q000517:prevention & control; D013211:Staphylococcus aureus; D018089:Superantigens / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000502:physiology
chemical_list: D001427:Bacterial Toxins; D018106:CD28 Antigens; D004768:Enterotoxins; D018089:Superantigens; D014409:Tumor Necrosis Factor-alpha; C030107:enterotoxin F, Staphylococcal; D007371:Interferon-gamma