Temporal relationship of cytokine release by peripheral blood mononuclear cells stimulated by the streptococcal superantigen pep M5

Abstract

We undertook this study to determine the quality, quantity, and temporal relationship of pep M5-induced cytokine release. The ability of pep M5 to stimulate interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF-α) production by a T-cell-depleted, monocyte- and B-cell-enriched cell population was dependent on the presence of T cells. The requirement for T cells could be met by addition of exogenous gamma interferon (IFN-γ). In the presence of IFN-γ, pep M5 induced the release of TNF-α, IL-1, and IL-6. TNF-α levels peaked at 24 h, while IL-1 and IL-6 levels peaked at 48 h. pep M5 induced T cells to produce IFN-γ, which may have accounted for the ability of the superantigen to induce the production of IL-1, IL-6, TNF-α, and TNF-β by peripheral blood mononuclear cells (PBMC). The addition of excess IFN-γ to cultures of pep M5 and PBMC did not further increase the release of these cytokines at 24 and 48 h but resulted in sustained higher levels at 72 h. Interestingly, TNF-β production occurred only in the presence of pep M5 and exogenous IFN-γ. The ability of pep M5 to induce cytokine production was compared with that of a potent superantigen, staphylococcal enterotoxin B (SEB). SEB was a 2- to 14-fold-more-potent inducer of IFN-γ production. Furthermore, the profile of cytokine released by PBMC in response to this superantigen mimicked that seen with pep M5 in the presence of exogenous IFN-γ. In conclusion, pep M5 induces the production of cytokines that are involved in immune regulation and inflammation. These cytokines also play a major role in human T-cell responses to this superantigen.