Interferon gamma (IFN g ) & interleukin-4 (IL-4) gene variants & cytokine levels in pulmonary tuberculosis.

Vidyarani, M.; Selvaraj, P.; Prabhu Anand, S.; Jawahar, M.S.; Adhilakshmi, A.R.; Narayanan, P.R.

Indian Journal of Medical Research; 2006; 124; 403-410.

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 g +874A and IL-4 -590T polymorphisms were associated with susceptibility to pulmonary tuberculosis as well as the level of IFN g and IL-4 in south Indian population.

Methods : Interferon g +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 g 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 g genotypes and IFN g 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 g +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.

Keywords: Cytokine - IFN g - IL-4 - polymorphism – tuberculosis

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