The genetic variations investigated were shown to influence the levels of the cytokines IFN-γ, IL-6, IL-4, and IL-10; however, the genotype and wild-type allele for IFNG +874A/T and the genotype and polymorphic allele for IL4 -590C/T appear to be more relevant in the context of Mtb infection, which has been associated with the development of TB among individuals infected by the bacillus and with susceptibility to active infection but not with susceptibility to latent infection. Here, IL4 is linked to disease arising from reactivation of latent virus.