Expression of T-cell receptor Vβ2 and type 1 helper T-cell-related cytokine mRNA in streptococcal pyrogenic exotoxin-C-activated human peripheral blood mononuclear cells

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Abstract
Streptococcal pyrogenic exotoxin type C (SPE C) is a member of the bacterial superantigens that are potent stimulants of T cells. We expressed SPE C in Escherichia coli and characterized its selective stimulation properties on human T cells bearing specific Vβ chains of T-cell receptors (TCRs). Cytokine profiles induced by SPE C were also examined. Recombinant SPE C significantly enhanced proliferation of human peripheral blood mononuclear cells (PBMCs) at concentrations as low as 10−12–10−14 M. Reverse transcription of RNA from SPE-C-stimulated PBMCs followed by polymerase chain reaction, revealed selective induction of TCR Vβ2 chain expression. SPE C raised the mRNA level of type 1 helper T cell (TH1) related cytokines, such as interferon γ (IFN-γ), interleukin 2 (IL-2), and tumor necrosis factor β (TNFβ). The expression of TNFα was also increased. In contrast, the increase in mRNA levels of the p35 small fragment of IL-12 and type 2 helper T cell (TH2) related cytokines (i.e., IL-4 and IL-10) was not significantly affected by SPE C. The mRNA level of proinflammatory cytokine IL-6 was increased marginally. Consistent with the mRNA accumulation, protein concentrations of IFNγ, IL-2, and TNF were increased in SPE-C-stimulated PBMCs, but IL-4 was not. From these results, we conclude that the stimuli of SPE C preferentially causes the TH1 responses in human T cells bearing TCR Vβ2.Key words: streptococcal pyrogenic exotoxin C, Streptococcus pyogenes, T cells, cytokine, superantigen.

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