A loss of antigen-specific T-cell responses due to defective cytokine signaling during infections has not been reported. We hypothesize that tuberculosis can destroy signaling effects of selective cytokine(s) and induce exhaustion of antigen-specific T cells. To test this hypothesis, mechanistic studies were performed to examine whether and how tuberculosis blocked interleukin 23 (IL-23) and interleukin 2 (IL-2) signaling effects on a major human γδ T-cell subpopulation, phosphoantigen HMBPP-specific Vγ2Vδ2 T cells. IL-23 and IL-2 significantly expanded HMBPP-stimulated Vγ2Vδ2 T cells from subjects with latent tuberculosis infection, and IL-2 synergized the effect of IL-23. IL-23-induced expansion of Vγ2Vδ2 T cells involved STAT3. Surprisingly, patients with tuberculosis exhibited a selective destruction of IL-23-induced expansion of these cells. The tuberculosis-driven destruction of IL-23 signaling coincided with decreases of expression and phosphorylation of STAT3. Interestingly, impairing of STAT3 was linked to marked increases in the microRNAs (miRNAs) hsa-miR-337-3p and hsa-miR-125b-5p in Vγ2Vδ2 T cells from patients with tuberculosis. Downregulation of hsa-miR-337-3p and hsa-miR-125b-5p by miRNA sponges improved IL-23-mediated expansion of Vγ2Vδ2 T cells and restored the ability of these cells to produce anti-tuberculosis cytokines. These results support our hypothesis that tuberculosis can selectively impair a cytokine effect while sparing another and can induce exhaustion of T cells in response to the respective cytokine.
Keywords: JAK2/STAT3; T-cell exhaustion; Vγ2Vδ2 T cells; cytokine signaling; miRNA; tuberculosis.
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