SMAD7 and cytomegalovirus infection: HCMV infection of precursor monocytes leads to the generation of toll-like receptors (TLRs) responsive inflammatory macrophages resistant to down-regulatory stromal TGF-β, allowing the macrophages to react to invading pathogens and immunostimulatory products with inflammation mediated by the Smad7 cytokine response 61.Within the innate immune system, natural killer (NK) cells act as the first line of defense and play an important role in limiting early cytomegalovirus (CMV) infection 62.