Alteration of serum inflammatory cytokines in active pulmonary tuberculosis following anti-tuberculosis drug therapy

Active pulmonary tuberculosis (APTB) is associated with a failure of the host immune system to control the invading Mycobacterium tuberculosis (Mtb). The objective of this study was to quantify and assess the role of serum inflammatory cytokines in active pulmonary tuberculosis patients following anti-tuberculosis drug (ATD) therapy. Blood samples were collected from APTB patients and normal healthy subjects (NHS) (total n = 204) at baseline and 2, 4 and 6 months post-therapy and the abundance of serum inflammatory cytokines were measured by cytokine specific ELISA. Compared to NHS, APTB patients at baseline had higher levels of serum pro-inflammatory cytokines IL-12p40 (P < 0.001), IFN-γ (P < 0.001), TNF-α (P < 0.01), IL-1β (P < 0.001) and IL-6 (P < 0.001) and anti-inflammatory cytokines IL-10 (P < 0.001) and TGF-β1 (P < 0.001) while there was no change in the level of IL-4. In APTB patients, the serum levels of IFN-γ, TNF-α, IL-6 and TGF-β1 directly relate to the bacterial load while the TNF-α, IL-1β, IL-6 and TGF-β1 relate to radiological severity. At baseline, the IL-6 level in NHS and APTB patients differed most and following ATD therapy, this level rapidly decreased and stabilized by 4-month in APTB patients. It is concluded that a subtle reduction in the serum level of IL-6 of the APTB patients following ATD therapy might play a vital role in immune-protection of the host against Mtb infection and hence the serum IL-6 level can be a useful marker to diagnose the effectiveness of therapy in the patients.