Considering the role of T-bet, GATA3, FOXP3, and EOMESin T-cell development, differentiation, and memory formation, as well as cytokine production, and the scarcity of studies evaluating their expressions after PRRSV infection, the following work aimed to evaluate the expressions of these TFs in target organs, namely, the lung, tracheobronchial lymph node, and the thymus, and the expressions of different effector cytokines (IFN-γ, TNF-α, and IL-10) and FasL produced by T-cell polarization during the early phase of infection with PRRSV-1 strains of different virulence. The gene discussed is TNF; the disease is infection.