The T cell response to MTB is restricted to a CXCR3⁺CCR6⁺ memory subset.

<p>(A, B) Three CD45RA⁻CD25⁻CD4⁺ memory T cell subsets from four LTBI donors were sorted; 1) CCR6⁺CXCR3⁻; 2) CCR6⁺CXCR3⁺; and 3) CCR6⁻. (A) Representative dot plot from one donor; (B) Median percentages of the T cell subsets on total CD4⁺ memory T cells. Error bars indicate interquartile range (n = 4). (C) T cell libraries were set up from the sorted subsets by polyclonal stimulation and expansion for 3–4 weeks. Libraries were analyzed by stimulation with autologous monocytes with or without MTB whole cell lysate and proliferative response was measured by ³H-thymidine incorporation. Shown is the estimated frequency of MTB-specific T cells per 10⁶ CD4 memory T cells for LTBI donors. (D) Distribution of MTB-specific T cells in the three memory T cell subsets. Data represent median ± interquartile range from four donors. Mann Whitney test, *, <i>p</i><0.05.