A loxP site was inserted upstream of exon 2 (at site 10310) and an FRT flanked neo cassette and loxP site were inserted downstream of exon 4 (at site 12190) via homologous recombination. Recombinase mediated recombination removed the neo cassette and exons 2-4. PCR of a spontaneous mutation in the C57BL/6J Cd1d2 gene confirmed integration in the C57BL/6J allele. (J:210436)