Identification of M. tuberculosis-specific Th1 cells expressing CD69 generated in vivo in pleural fluid cells from patients with tuberculous pleurisy

Th1 cell-mediated immune responses at the site of active infection are important to restrict the growth of M. tuberculosis (MTB) and for the spontaneous resolution of patients with tuberculous pleurisy (TBP). In the present study, we found that without any stimulation, CD4(+) T cells in pleural fluid cells (PFCs) from patients with TBP expressed significantly higher levels of CD69 than PBMCs from patients with tuberculosis (TB) or healthy donors. CD4(+)CD69(+) T cells expressed T-bet and IL-12Rβ2. After stimulation with MTB-specific antigens, CD4(+)CD69(+) T cells expressed significantly higher levels of IFN-γ, IL-2 and TNF-α than CD4(+)CD69(-) T cells, demonstrating that CD4(+)CD69(+) T cells were MTB-specific Th1 cells. In addition, CD4(+)CD69(+) T cells were mostly polyfunctional Th1 cells that simultaneously produced IFN-γ, IL-2, TNF-α and displayed an effector or effector memory phenotype (CD45RA(-)CCR7(-)CD62L(-)CD27(-)). Moreover, the percentages of CD4(+)CD69(+) T cells were significantly and positively correlated with polyfunctional T cells. Interestingly, sorted CD4(+)CD69(+) but not CD4(+)CD69(-) fractions by flow cytometry produced IFN-γ, IL-2 and TNF-α that were significantly regulated by CD4(+)CD25(+) Treg cells. Taken together, based on the expression of CD69, we found a direct quantitative and qualitative method to detect and evaluate the in vivo generated MTB-specific polyfunctional CD4(+) T cells in PFCs from patients with TBP. This method can be used for the potential diagnosis and enrichment or isolation of MTB-specific Th1 cells in the investigations.