A neomycin resistance cassette with a 5' loxP site was inserted upstream of Cd3e. A Rox-flanked hygromycin resistance cassette with a 5' loxP site was inserted downstream of Cd3g. Cre- and Dre-mediated recombination removed Cd3e, Cd3d and Cd3g along with both selection cassettes. (J:243702)