Interferon gamma gene +874A/T polymorphism and intracellular interferon gamma expression in pulmonary tuberculosis

We investigated whether IFN-gamma gene +874(A/T) polymorphism influences intracellular interferon gamma expression in T-cell subsets of normal healthy subjects (NHS) and pulmonary tuberculosis patients (PTB). Peripheral blood mononuclear cells were stimulated with live Mycobacterium tuberculosis (MTB) and the intracellular IFN-gamma expression was studied using flow cytometry. Genotyping of IFN-gamma gene +874(A/T) was done using allele specific polymerase chain reaction. Significantly increased IFN-gamma expressing CD3+CD4+ and CD3+CD8+ T cells were observed in NHS with AA genotype compared to TT genotype in unstimulated (p=0.0308 and p=0.0157) and MTB stimulated (p=0.0494 and p=0.0287) cultures and this difference was not observed in PTB patients. The present study suggests that the variant genotypes of IFN-gamma (+874) may be associated with altered expression of IFN-gamma at the intracellular level and play an immunoregulatory role at the site of M. tuberculosis infection.