Cre-mediated excision of the parental Il2rbtm1a(EUCOMM)Hmgu allele resulted in the removal of the promoter-driven neomycin selection cassette and critical exon(s) leaving behind the inserted lacZ reporter sequence. Further information on targeting strategies used for this and other IKMC alleles can be found at http://www.informatics.jax.org/mgihome/nomen/IKMC_schematics.shtml.