An FRT-flanked neomycin resistance cassette with a 5' loxP site was inswerted upstream of exon 2. An additional loxP site was inserted downstream of exon 3. Cre-mediated recombination removed exon 2, exon 3 and the neomycin resistance cassette. Western blot analysis confirmed the absence of protein expression in the spleen. (J:201008)