IKZF1 binds and activates the enhancer (delta-A element) of the CD3-delta gene. It functions in the specification and the maturation of the T-lymphocyte. It also interacts with a critical control element in the TDT (terminal deoxynucleotidyltransferase) promoter as well as with the promoters for other genes expressed during early stages of B- and T-cell development.