Comparative analysis of spontaneous and mycobacterial antigen-induced secretion of Th1, Th2 and pro-inflammatory cytokines by peripheral blood mononuclear cells of tuberculosis patients

The cytokines produced by T helper (Th)1 cells (IFN‐γ, IL‐2 and TNF‐β) correlate with protection, whereas the cytokines released by Th2 cells (IL‐4, IL‐5) and the anti‐inflammatory cytokine IL‐10 correlate with pathogenesis of tuberculosis (TB). However, the pro‐inflammatory cytokines (IL‐1β, IL‐6, IL‐8, TNF‐α and IL‐12p70) are responsible for both protection and pathogenesis of TB. The aim of this work was to carry out a comparative analysis of cytokines present in early (day 2) and late (day 6) cultures of peripheral blood mononuclear cells (PBMCs) obtained from pulmonary tuberculosis patients. PBMCs were cultured in vitro in the absence and presence of exogenously added complex mycobacterial antigens and RD1 peptide pool. The supernatants were collected on day 2 and day 6 of culture and assayed for secreted cytokines using the flow cytomix assay. All of the cytokines, except for IL‐12p70, were spontaneously secreted by PBMCs of 27–100% TB patients, but only TNF‐α concentration was significantly higher on day 2 than day 6 (P < 0.05). Two days following antigenic stimulation, only IL‐1β, IL‐6, TNF‐α and IL‐10 were secreted in response to some mycobacterial antigens. However, 6 days later, all of the cytokines, except for IL‐2, IL‐4, IL‐5 and IL‐8, were secreted significantly in response to all complex antigens and RD1 peptides, compared with the non‐stimulated cultures (P < 0.05). In conclusion, the study shows that the longer in vitro stimulation time (6 days) was necessary for the optimal induction of IFN‐γ and TNF‐β, and practically convenient for the detection of IL‐10, IL‐1 β, TNF‐α and IL‐6.