The T-box gene family consists of transcription factors characterized by a related DNA-binding domain (T-box) of approximately 200 amino acids. The T-box genes exhibit diverse temporal and spatial patterns in the developing embryo. TBX21 is a member of a phylogenetically conserved family of proteins that share a common DNA-binding domain, the T-box. TBX21 is the human ortholog of mouse Tbx21/Tbet protein. Studies in mouse show that Tbx21 protein is a Th1 cell-specific transcription factor that controls the expression of the hallmark Th1 cytokine, interferon-gamma (IFNG). Expression of the human ortholog also correlates with IFNG expression in Th1 and natural killer cells, suggesting a role for this gene in initiating Th1 lineage development from naive Th precursor cells.
