Cytokine production by resting and anergic T cells upon challenge with Ag-loaded APCs. Production of (A) IL-4, (B) IL-6, (C) IL-10, (D) IL-2, and (E) IFN-γ by resting and anergic Fel d 1 p4 T cells as measured by cytometric bead array. (F) Supernatant IFN-γ and IL-2 for resting and anergic 7P.73 T cells incubated with Ag-loaded APCs was assessed by ELISA and CTLL proliferation, respectively. Error bars depict the SD of triplicates in a single experiment. (G) Intracellular cytokine staining for IFN-γ and IL-2 by resting and anergic T cells was assessed by flow cytometry. Dot plots and the percentage of cells in each quadrant for IL-2 and IFN-γ staining of resting and anergic Fel d 1 p4 T cells after mixing with Ag-loaded APCs are shown. Unexpectedly, anergic cells produce IFN-γ upon rechallenge. All data are representative of at least 2 independent experiments.