A targeting vector was designed to insert a cre recombinase cDNA, an frt-flanked neo cassette, and an internal ribosome entry site (IRES) into the Il2 gene just upstream of the first codon. The mice with correct targeted inserts were bred with Actin-FLPe females (on a C57BL/6 congenic background) to remove the neo selection cassette. (J:231266)