In this study, we demonstrated evidence for the induction of CD80+ monocytes by staphylococcal enterotoxin B (SEB) via caspase actions. Pre-treatment with pyrrolidine dithiocarbamate (PDTC), a potent inhibitor of NF-kappaB, resulted in a significant reduction in the percentage of SEB- and interferon-gamma (IFN-gamma) (produced by SEB) -induced CD80+ monocytes. SEB and IFN-gamma activated NF-kappaB, which was inhibited by PDTC. SEB induced the activation of caspase-3 and -8, and pre-treatment with z-VAD-fmk, a broad-spectrum inhibitor of caspases, prevented the induction of apoptosis. Treating with z-VAD-fmk resulted in a reduction of the generation of CD80+ monocytes. These results indicated that CD80 driven by NF-kappaB is regulated by the enzymatic actions of caspases, which allows monocytes to participate in massive T-cell activation.
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