Tuberculosis is an infectious disease which caused by Mycobacterium tuberculosis
(M. tuberculosis) that infected numerous organ especially the lung. A person's immunity is
very affecting for a person exposed to pulmonary tuberculosis. T-helper-1 cell (Th1) is very
influential in the immune system especially in interfering intracellular bacterial infection. One
of the cytokines known produced by Th1 cell is interferon gamma (IFN-γ) which is in
eliminating M. tuberculosis. The study aims to identify the association between level of IFN-γ
and AFB positivity in pulmonary tuberculosis patients in Medan.It is a case-control study. The
subjects of the study were 60 new cases of pulmonary tuberculosis with AFB sputum smearpositive
that never received ATT consisting 20 cases AFB (+1), 20 cases AFB (+2) and 20
cases AFB (+3).Samples were plasma collected from the venous blood of pulmonary
tuberculosis patients. The plasma then underwent laboratory assay with ELISA techniques.
Independent t-test was p<0.05 considered significant. Level of IFN-γ in TB AFB (+1) is higher
than TB AFB (+2) and (+3), with thesignificant statistical result (p=0.001).