Th17 cells respond to bacterial and fungal antigens. PB lymphocytes from cohorts of HIV-infected and uninfected persons were stimulated with a variety of viral (A) or bacterial antigens (B) overnight in the presence of brefeldin A and stained as in “Intracellular cytokine assay.” Production of IL-17 and IFN-γ by memory CD4 T cells in response to individual antigen-specific stimulation was measured by flow cytometry. (C) The frequencies of memory CD4 T cells from PB lymphocytes of several HIV⁺ (●) and HIV⁻ patients (○) producing either IFN-γ or IL-17 in response to bacterial or fungal antigens are shown.