STAT4 and infection: The impaired ability of hybrid Th1/Tfh to help antibody production is likely due to an antagonism regulating Tfh effector functions through the network of STAT4 and T-bet expression and the effects of IL-2, IL-12, IFN-γ, and/or TNF, depending on the infection (Fang et al., 2018; Weinstein et al., 2018).