TBX21 and viral infectious disease: In contrast to a normal T-bet expression in Egr2 or Egr3 single-deficient T cells, as well as Egr2 and 3 double-deficient T cells, a recent report showed defective IFN-γ production by Egr2-deficient T cells that was attributed to direct regulation of the Tbx21 and Ifng loci by Egr2 in T cells in response to viral infection (17).