Genotyping of IL-6 × G-CSFR–deficient mice. (A) Representative Southern blot analysis of Pst1-digested genomic tail DNA isolated from the progeny of IL-6 × G-CSFR double heterozygous mice. The filter was hybridized simultaneously with probe G and probe 6. A 4.2-kb or 1.1-kb band is detected from G-CSFR wild-type or mutant alleles, respectively. A 3.6-kb or 1.8-kb band is detected from IL-6 wild-type or mutant alleles, respectively. (B) Structure of the targeted mutations. The positions of probe G and probe 6 are shown. The structure of the wild-type and mutant IL-6 alleles were derived from Kopf et al.11