Interferon gamma (IFN -gamma) and interleukin -4 (IL-4) gene variants and cytokine levels in pulmonary tuberculosis. Indian Journal of Medical Research

Abstract

Background & objectives: Cytokine gene polymorphisms may alter Th1/Th2 balance with major implications in tuberculosis. The aim of our study was to find out whether Interferon � +874A and IL-4 -590T polymorphisms were associated with susceptibility to pulmonary tuberculosis as well as the level of IFN� and IL-4 in south Indian population. Methods: Interferon � +874A and IL-4 -590T promoter polymorphisms were studied in 129 pulmonary tuberculosis (PTB) patients and 127 normal healthy subjects (NHS) and were associated with culture filtrate and live Mycobacterium tuberculosis induced IFN� and IL-4 production in peripheral blood mononuclear cells (PBMCs). IL-4 gene variants were also associated with IgG antibody levels against M. tuberculosis culture filtrate antigen. Results: The variant IFN� genotypes and IFN� levels between genotypes did not differ significantly in patients and controls. Significantly increased frequency of variant IL-4 ‘CT’ genotype in PTB patients (P<0.05) and ‘CC’ genotype in control group (P<0.01) was observed. IL-4 levels were detectable in very few subjects and the IgG levels did not differ between the three IL-4 genotypes. Interpretation & conclusion: The study suggests a lack of functional association of Interferon � +874A polymorphism in tuberculosis in south Indian population. The higher frequency of IL-4 ‘CT’ genotype in PTB suggests a possible association of IL-4 -590T promoter polymorphism with susceptibility to tuberculosis, and the ‘CC’ genotype may be associated with protection