Mycobacterium tuberculosis (Mtb) infection remains one of the world’s major causes of illness and mortality. A clear understanding of the host defense against Mtb is imperatively needed forthe control of this epidemic. When tuberculosis (TB) infection occurs, a variety of pro and anti-inflammatory cytokines play a vital role in the pathogenesis of this disease. Interleukin-10 (IL-10) is one of the most important anti-inflammatory cytokines reported to suppress the protective immune response against tuberculosis.AimThe aim of the present study was to evaluate the association of plasma IL-10 levels with various disease stages of TB and the possible effects of treatment on these levels.Materials and methodsA group of 30 patients with active pulmonary TB and a control group of 21 healthy individuals were enrolled in this study. The levels of IL-10 were measured before, during, and after treatment using commercially available enzyme-linked immune-sorbent assay (ELISA). Data were analyzed using GraphPad Prism version 5.0.ResultsThe results showed that the levels of IL-10 had significant differences between the TB and control groups (p<0.05). The patients with abnormal chest X-Ray findings had higher IL-10 levels when compared to patients with normal X-Rays (p=0.03). A subgroup of 18 patients were followed during the treatment and the mean plasma concentration of IL-10 in patients before therapy was higher than in patients at 3 months of therapy and in patients after 6 months of therapy (p=0.01). However, the IL-10 level remained significantly higher in patients at the end of treatment compared with controls.These findings could be used in follow-up as clinical biomarker of the success of tuberculosis therapy.