Expansion of Vδ1 T cells is also observed in other viral infections, including HIV/SIV42–44, HBV45, CMV46, and human herpesvirus 8 (HHV-8) infections47, likely due to in situ and systemic activation driven by infected cells that can produce cytokines like TNF-α, IL-1, IL-6, and IL-18, as well as IFN signaling during acute and chronic viral infections. Here, TNF is linked to viral infectious disease.