TGFB1 and infection: Sabsabi et al., using γδ+ T knockout chickens, demonstrated that the absence of γδ+ T cells in MDV-infected chickens resulted in increased viral load in spleen and thymus as well as increased tumor incidence, suggesting an antiviral role early in the infection [57] However, Matsuyama et al., detected two distinct functional subsets of chicken γδ+ T cells (IFN-γ+ and TGF-β+).