CFP-10/ESAT-6-specific CD8 T cells in patients with TB have a short-lived, pro-apoptotic phenotype.

<p>PBMCs from individuals with LTBI (n = 18) and patients with TB disease (n = 20) were stimulated for 6 hours with CFP-10 and ESAT-6 peptide pools; intracellular IFN-γ production was measured in CD8 T cells by flow cytometry. (<b>A</b>) Frequencies of CFP-10 and ESAT-6-specific IFN-γ⁺ CD8 T cells in persons with LTBI and patients with TB disease. Horizontal lines represent the median. Data are shown after subtraction of background cytokine production in the negative control condition. The dotted line separates individuals who met the criteria for a positive CD8 T cell response for further phenotypic analyses (above dotted line: n = 6 LTBI; n = 13 TB disease), and individuals in whom the frequency of IFN-γ⁺ CD8 T cells was too low to meet the criteria for further phenotypic analyses (below dotted line). (<b>B</b>) Representative flow cytometry data from an individual with LTBI and a patient with TB disease, following stimulation of PBMCs with an ESAT-6 peptide pool. Grey cells indicate the total CD8 T cell population (gated on VIVID^l°CD3⁺CD8⁺ cells); black cells indicate ESAT-6-specific CD8 T cells (gated on VIVID^l°CD3⁺CD8⁺IFN-γ⁺ cells). (<b>C</b>) Summary data of the percentage of specific IFN-γ⁺ CD8 T cells expressing Ki67, Bcl-2, CD127, CD57 and CD95 in individuals with LTBI and TB disease. Differences were assessed using the Mann-Whitney test. § indicates p values that did not remain significant after applying the Bonferroni correction for multiple comparisons. (<b>D</b>) Comparison of the expression of intracellular Ki67 and Bcl-2 between the total CD8 T cell population and specific IFN-γ⁺ CD8 T cells within the same individual. Only individuals meeting the criteria for a positive CD8 T cell response in the ICS assay were included in this paired analysis (n = 6 LTBI; n = 13 TB disease). Differences were assessed using the Wilcoxon matched-pairs test.