The T-bet model was developed by Laurie H. Glimcher at Harvard University. The model was creeated by targeting the Tbx21 gene in TC-1 ES cells and injecting the targeted cells into blastocysts. Resultant chimeras were backcrossed to C57BL/6J for nine generations. Taconic received stock in 2004. The line was backcrossed to C57BL/6JBom for embryo transfer derivation (N10). The colony was maintained through incrossing homozygous mice.