IL-19 secreted predominantly by osteocytes regulates granulopoiesis. (A) Immunofluorescence microscopy of femur sections of 12-week-old Dmp1-TSC1, Dmp1-Rheb, and control mice. Cells were stained with anti-Dmp1 (red) and anti–IL-19 (green). Blue, nuclei visualized by DAPI stain. Scale bar, 50 µm. (B) Level of IL-19 or G-CSF in serum of 12-week-old Dmp1-TSC1, Dmp1-Rheb, and control mice was detected by enzyme-linked immunosorbent assay (ELISA) (mean ± SD; n = 10). (C) FACS analysis of CD11b⁺Gr-1⁺ and CD11b^intGr-1^int cell proliferation in the BM of 12-week-old Dmp1-TSC1 and control mice with bilateral intratibial injection into the marrow cavity with purified IL-19 antibody (25 μg/kg per day) for 14 days (mean ± SD; n = 10). (D) FACS analysis of PB CD11b⁺Gr-1⁺ neutrophils in purified IL-19 antibody–treated 12-week-old mice (mean ± SD; n = 10). (E) FACS analysis of CD11b⁺Gr-1⁺ and CD11b^intGr-1^int cell proliferation in the BM of 12-week-old Dmp1-Rheb and control mice IP injected with recombinant murine IL-19 (25 µg/kg per day) for 14 days (mean ± SD; n = 10). (F) FACS analysis of PB CD11b⁺Gr-1⁺ neutrophils in recombinant IL-19–treated 12-week-old mice (mean ± SD; n = 10). (G) FACS analysis of the proliferation of CD11b⁺Gr-1⁺ cells cultured in CM from 12-week-old Rheb- or TSC1-loss osteocyte cultures treated with IL-19 or IL-19 antibody (mean ± SD; n = 10). Data are mean ± SD of 3 independent experiments. **P < .01; ***P < .001. NS, not significant.