Antigen-independent effector function of TCRζ^dim T cells. (A) TCRζ^dim T cells were generated from purified T cells following stimulation for 7 days with IL-2, IL-6, and TNF-α in the absence of antigen or antigen-presenting cells. TCRζ expression is shown compared to that of unstimulated T cells. (B) TCRζ^dim T cells were cocultured with CHO cells expressing empty vector, CD80, or CD86 for 24 hours. Supernatants were harvested and IFN-γ and IL-10 levels determined by ELISA. (C) Resting (TCRζ^bright) or activated TCRζ^dim T cells were fixed prior to coculture at the indicated ratios with purified monocytes. Supernatants were harvested 24 hours later and TNF-α levels determined by ELISA. Supernatants derived from cultures of monocytes or T cells alone or LPS-stimulated monocytes were used as negative and positive controls, respectively. Data are representative of multiple experiments, and represent mean cytokine levels ± SD in panels B and C.