Association of rs3212220 G/T single nucleotide polymorphism of IL-12B with tuberculosis in the population of Punjab, India

Many single nucleotide polymorphisms (SNPs) in the cytokine genes are reported to be associated with altered host susceptibility to tuberculosis (TB). Interleukin (IL)-12 has crucial role in immunity against Mycobacterium tuberculosis (MTB), the causative organism of TB. IL-12 is a key cytokine required for the release of IFN-γ by NK and Th1 cells, which is regarded as pivotal cytokine against TB. IL-12 has two subunits IL-p35 and IL-12p40 encoded by IL-12A and IL-12B gene respectively. Present study was designed for evaluating the association of rs3212220 G/T SNP of IL-12B and to check plasma levels of IL-12p40 in TB patients from population of Punjab, India. This case-control study was conducted on 300 TB patients and 150 normal healthy controls (NHCs). Genotyping of selected SNP of IL-12B was done by amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) method. Plasma levels of IL-12p40 were measured by enzyme linked immunosorbent assay (ELISA). Statistical significance level was calculated at 0.05. No statistically significant difference was found between genotypic and allelic frequencies of rs3212220 G/T SNP of IL-12B among TB patients and NHCs. IL-12p40 levels were found to be significantly elevated in TB patients when compared with NHCs ( p  < 0.0001). These levels declined with the course of anti-tuberculosis therapy (ATT). GG and GT genotypes were found to be associated with increased level of IL-12p40 in TB patients when compared to NHCs.