IFNG and viral infectious disease: The SNP (+874T/A, rs2430561) of IFN-γ gene, a T-to-A transition at +874 loci in the 1st intron of IFN-γ gene, is complete linkage disequilibrium with the12 CA repeat microsatellite and correlated with IFN-γ production.7 Moreover, the transcription factor nuclear factor kappa-B (NF-κB) binds preferentially to the +874T allele, which is known to upregulate the expression of IFN-γ.8 The +874T/A polymorphism generates 3 genotypes (TT, TA, and AA), and TT genotype produces a high level of IFN-γ, helps the host's defense against viral infection.