6). Interestingly, high levels of IL-22 were also detected
in the Ivacaftor cell line serum samples of individuals with latent (P = 0·002) and active TB infection (P = 0·003) compared to healthy controls (Fig. 6). IL-1β concentrations in serum of individuals with latent TB infection were increased significantly compared to healthy individuals (P = 0·02). The levels of IL-1β were also higher in individuals with active TB infection but were not statistically significant. Significantly elevated levels of IL-8 were detected in the serum of individuals with latent TB infection only. Mean IL-8 concentrations were significantly higher in latent TB group compared to healthy controls (P < 0·0001). However, the levels of IL-8 were higher but not statistically significant in individuals with active TB infection when compared to healthy individuals (Fig. 6); there was
no difference in the circulating levels of IL-17, IFN-γ (Fig. 6), IL-12p70, IL-2 and TNF-β (data not shown) in serum samples of healthy, latent and active TB subjects. The mean levels of IL-4 in serum of individuals with latent and active TB infection were significantly higher (P = 0·02) than the levels found in healthy subjects (Fig. 6). Levels of IL-5 and IL-10 cytokines were below the detection limit in both antigen-stimulated PBMC culture supernatants as well as in serum samples in all three groups of individuals (data not shown). The present study demonstrates find more differential induction of IFN-γ-, IL-17- and IL-22-expressing CD4+ T cells in Parvulin circulation and following specific stimulation with mycobacterial antigens in TST-negative healthy controls, TST-positive latent and active TB subjects. While the expression of IFN-γ and other cytokines has been analysed in human plasma and PBMC supernatants ex vivo[32,33], the levels of IL-17- and IL-22-expressing CD4+ T cells
and granulocytes in the whole blood of TB patients is not well reported. Herein, we show that the percentage of individuals with active TB expressing IL-17-, IL-22- and IFN-γ-producing CD4+ T cells were decreased significantly compared to the individuals with latent TB infection and healthy controls (Fig. 1). However, such differences were not found in CD8+ T cells (data not shown). The reasons for the decreased IFN-γ-, IL-17- and IL-22-expressing CD4+ T cells in the circulation remain unclear. The differential expression of cytokines in circulation and in affected tissues such as lungs, spleen and lymph nodes have been described in tuberculosis [23,34]. It is possible that antigen-specific IFN-γ-, IL-17- and IL-22-producing CD4+ T cells are recruited to the affected tissues by chemokines released by infected resident macrophages and dendritic cells.