We present evidence that toxic shock syndrome toxin 1 (TSST-1) induces the production of high levels of TNF by human blood monocytes. Enriched lymphocyte preparations incubated with the staphylococcal toxin produced significant levels of TNF-like activity that is not neutralized by anti-rHuTNF antibodies and is likely to be lymphotoxin (LT or TNF-beta). We demonstrate also that TSST-1 is a potent inducer of IFN-gamma. When lymphocyte preparations were costimulated with PMA, the TSST-1 effect was strongly potentiated and the levels of cytotoxic factors, IFN-gamma, and IL-2 present in supernatant fluids were comparable to those observed after treatment with PMA and PHA. Thus, TSST-1, which is also known as an inducer of IL-1 and IL-2, stimulates the production of endogenous mediators that could play a role in the physiopathological processes of toxic shock syndrome (TSS). The described results suggest that the discrepancies in the clinical features between TSS and endotoxin shock may be related to qualitative differences in cytokine production.

Lipopolysaccharide-induced necrosis of grafted tumors was potentiated by several hydrophilic and lipophilic muramyl dipeptide (MDP) derivatives administered a few hours prior to small amounts of lipopolysaccharide (LPS) in spite of low titers of induced circulating tumor necrosis factor (TNF). However, pretreatment with MDP derivatives did increase the level of TNF in the blood of mice challenged by a greater dose of LPS. The TNF amount in 2 h postendotoxin mouse serum reached a peak when the glycopeptide had been given 6 h before the challenge, being approximately 100-fold above that obtained in unprimed mice. The cytotoxic activity in mouse serum was inhibited by rabbit antibodies raised against recombinant mouse TNF. Although there exists a toxic synergism between BCG or MDP and endotoxin, the effect of certain MDP derivatives was not related to an increased susceptibility to the toxicity of LPS.

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