Superantigen-mediated lethal shock: the functional state of ligand-reactive T cells

Distinct functions of interferon-gamma for chemokine expression in models of acute lung inflammation

Challenge of the immune system with bacterial superantigens or endotoxin induces the systemic release of cytokines followed by lethal septic shock. The lung is particularly susceptible to systemic toxin exposure resulting in acute leucocyte infiltration and vascular damage. In the present study, the functions of interferon-gamma (IFN-gamma) and tumour necrosis factor (TNF) for chemokine regulation during acute lung inflammation were examined. Following administration of the superantigen, staphylococcal enterotoxin B (SEB), lung mRNA levels of the chemokines cytokine-induced neutrophil chemo-attractant (KC), lipopolysaccharide-induced CXC chemokine (LIX), macrophage chemotactic protein-1 (MCP-1), macrophage inflammatory protein (MIP)-1alpha and MIP-2 were increased to a similar extent both in controls and in mice deficient for the IFN-gamma or 55 000 MW TNF receptors. In contrast, interferon-inducible protein-10 (IP-10) and monokine induced by IFN-gamma (Mig) mRNA expression was markedly reduced in mice deficient for IFN-gamma or IFN-gamma receptor, but not in 55 000 MW TNF receptor knockout mice. In situ hybridization experiments demonstrated that IP-10 was highly expressed in lung interstitial macrophages of C57BL/6, but not of IFN-gamma receptor-deficient mice. In contrast to SEB administration, treatment with lipopolysaccharide resulted in a strong induction of IP-10 and Mig in IFN-gamma receptor-deficient mice. Together, these results establish a critical function of IFN-gamma for chemokine induction in acute lung inflammation that is dependent on the nature of the inflammatory stimulus.

Induction of selective anergy by toxic shock syndrome toxin-1 in CD8+ T cells

Interferon-gamma (IFN-gamma) mRNA expression of murine splenic CD8+ T cells in response to toxic shock syndrome toxin-1 (TSST-1) was examined in vitro. In primary response to TSST-1, purified CD8+ cells expressed a low frequency of IFN-gamma mRNA and produced very little interleukin-2 (IL-2) compared with unseparated lymphocytes and purified CD4+ cells. The addition of IL-2 to the cell culture enhanced IFN-gamma mRNA expression in the CD8+ population. Upon restimulation with TSST-1, no IL-2 production and hardly any IFN-gamma mRNA expression were observed in the purified CD8+ lymphoblasts. Exogenously added IL-2 did not increase the IFN-gamma mRNA expression in purified CD8+ blasts exposed to TSST-1. In contrast, stimulation with concanavalin A induced a high frequency of IFN-gamma mRNA in purified CD8+ blasts. Moreover, TSST-1 induced strong IFN-gamma mRNA expression in unseparated T lymphoblasts and purified CD4+ populations. Interestingly, a combined immunocytochemistry and in situ hybridization technique showed a high frequency of CD8+ IFN-gamma mRNA-expressing cells in an unseparated blast population. These results demonstrate that TSST-1 induces a selective anergy within the purified CD8- T-cell compartment and that the IFN-gamma mRNA expression in CD8+ T blasts can be achieved by stimulation of unseparated T cells with TSST-1.