Normal mice and IL-17a−/− mice that received antibody to IL-22 had more rapid bacterial dissemination outside of the lungs [30]. Therefore, we considered that IFN-γ and IL-22 mediated protective immune response to M. tuberculosis. In the present study, soluble IL-17 could not be detected in pleural fluid from patients with TBP. The low levels of IL-17 in patients with TBP might be because of the inhibition of Th1 conditions at the site of disease. Murine studies demonstrated that IFN-γ limited the Th17 lineage formation in vitro [31, 32]. IL-17 in bronchoalveolar lavage fluid and pleural fluid from most subjects,

even this website in the absence of inhibitory Th1 cytokines, was too low to be directly detected by ELISA [33–35]. Other studies showed that in patients with neutrophilic airway inflammation following exposure to organic dust, IL-17 level of bronchoalveolar lavage fluid was also undetectable,

except in those with the most severe inflammation [36]. However, the IL-17 expression by PFMC at both mRNA and protein levels was increased by stimulation with dominant peptides of ESAT-6, CFP-10 or BCG in vitro. This indicated that M. tuberculosis-specific Th17 cells were present at the local site of disease, but pathogen-related factors hampered the ability of the Th17 cells to provide protective immune response. Hence, it was likely that the immune response to M. tuberculosis buy MK-8669 infection was much more complicated in vivo than which was revealed by in vitro stimulation. The mechanisms in this process would be the focus of future studies. Our findings of ESAT-6-, CFP-10- or BCG-specific Th1, Th22 and Th17 cells in tubercular pleural fluid were consistent with studies from Scriba et al. [42]. They found the presence of two mycobacterium-specific CD4+ T cell populations in peripheral blood of persons exposed to or diseased by M. tuberculosis. The presence of these M. tuberculosis-specific T cells in pleural fluid might be because of the selective recruitment of specific cells

to the site of infection. This would be consistent with previous studies, which suggested that low Th1 frequencies at the periphery might result from T cells homing to the site of infection [37–39]. We found second that IL-22 and IL-17 were produced mainly by CD4+ T cells, which was consistent with results from Khader et al. [19] and in contrast to data from a murine model that showed that after mycobacterium infection, γδ T cells were the main source of IL-17 in the lungs [40]. We demonstrated that ESAT-6-, CFP-10- or BCG-specific Th22 and Th17 cells were distinct from each other and from Th1 cells. This was consistent with our previous study showing that IL-22-producing CD4+ T cells specific for Candida albicans were different from Th1, Th2 and Th17 cell subsets [41]. Thomas et al.