Results: We observed reduced secretion of IFN-γ and TNF-α in patients with HIV/TB co-infection compared to patients with HIV and TB mono-infections: IFN-γ—1.7- and 2.3 (p = 0.002); TNF-α—1.6- and 2.1- (p = 0.002), respectively. The gene discussed is IFNG; the disease is tuberculosis.