IL-6 contributes to the high level of bone formation in gp130Y757F/Y757F mutant mice. (a) Representative images of von Kossa–stained tibiae from 16-week-old WT, F/F, and F/F:IL-6–/– (F/F:IL-6) mice. Scale bar (white), 500 μm. (b) BV/TV and Tb.N are reduced further in F/F:IL-6–/– mice compared with WT and F/F mice. Tb.Sp, trabecular separation. (c) Deletion of IL-6 rescues the high ObS/BS and reduces the OV/BV of F/F mutant mice but not the high OcS/BS. All values are mean ± SEM from six female mice per group at 14–16 weeks of age. *P < 0.05; **P < 0.01; ***P < 0.001 vs. WT; ++P <0.01, +P < 0.05 vs. F/F.