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Interferon gamma (IFNγ) & interleukin-4 (IL-4) gene variants & cytokine levels in pulmonary tuberculosis
Reprint requests: Dr P. Selvaraj, Assistant Director, Department of Immunology, Tuberculosis Research Centre (ICMR), Mayor V.R. Ramanathan Road, Chetput, Chennai 600031, India e-mail: psraj21@hotmail.com
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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 γ +874A and IL-4 -590T polymorphisms were associated with susceptibility to pulmonary tuberculosis as well as the level of IFNγ and IL-4 in south Indian population.
Methods:
Interferon γ +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 IFNγ 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 IFNγ genotypes and IFNγ 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 γ +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.
