Finally viral-specific infections may be necessary for NK deficiencies in CFS given that the Human Immunodeficiency Virus type 1 Viral Protein R (HIV-1 Vpr) upregulates TGF-β and decreases macrophage production of IL-12 causing a decline in cytotoxic activity and IFN-γ [54]. Here, TCN1 is linked to myalgic encephalomeyelitis/chronic fatigue syndrome.