The bacterial artificial chromosome, RP24-227B3, containing the entire Il22 gene plus upstream (30 kb) and downstream (2 kb) regulatory sequences was modified to insert EGFP cDNA downstream of the Il22 exon 1 followed by an FRT-flanked neomycin cassette. The neomycin cassette was later removed using FLP recombinase leaving one FRT site. (J:286232)