An FRT- and loxP-flanked neomycin resistance cassette was inserted upstream of exon 2. An additional loxP site was inserted into exon 3 downstream of the coding sequence. Flp-mediated recombination removed the neomycin resistance cassette. Cre-mediated recombination removed the coding sequence of exon 2 and 3. Western blot analysis confirmed the absence of protein expression on CD4+ T cells. (J:204829)