IL-19 promotes granulopoiesis through IL-20Rβ/STAT3 signaling. (A) FACS analysis of IL-20Rβ levels in Gr-1⁺, Ter119⁺, B220⁺, and F4/80⁺ cells in the BM of 12-week-old mice (mean ± SD; n = 6). (B) Expression levels of IL-20Rβ in skin cells and BM Gr-1⁺ cells in 12-week-old mice were detected by western blotting. (C) FACS analysis of IL-20Rα in Gr-1⁺, Ter119⁺, B220⁺, and F4/80⁺ cells in the BM of 12-week-old mice (mean ± SD; n = 6). (D) Expression levels of IL-20Rα in colon cells and BM Gr-1⁺ cells in 12-week-old mice were detected by western blotting. (E) Immunofluorescence microscopy of femur sections of 12-week-old Dmp1-TSC1, Dmp1-Rheb, and control mice. Cells were stained with anti–Gr-1 (red) and anti–p-STAT3 (green). Blue, nuclei visualized by DAPI stain. Scale bar, 30 µm. (F) FACS analysis of BM and PB Gr-1⁺p-STAT3⁺ cells in 12-week-old Dmp1-TSC1 and control mice (mean ± SD; n = 10). (G) FACS analysis of BM and PB Gr-1⁺p-STAT3⁺ cells in 12-week-old Dmp1-Rheb and control mice (mean ± SD; n = 10). (H) Immunofluorescence microscopy of femur sections of 12-week-old Dmp1-Rheb and control mice IP injected with recombinant murine IL-19 (25 µg/kg per day) for 14 days. Cells were stained with anti–Gr-1 (red) and anti–p-STAT3 (green). Blue, nuclei visualized by DAPI stain. Scale bar, 30 µm. (I) FACS analysis of BM and PB Gr-1⁺p-STAT3⁺ cells in recombinant IL-19–treated 12-week-old mice (mean ± SD; n = 10). (J) Dmp1-TSC1 and control mice with bilateral intratibial injection into the marrow cavity with IL-20Rβ or negative control (NC) siRNAs for 10 days. The efficiency of IL-20Rβ siRNAs for IL-20Rβ in BM cells was measured by western blotting. (K) FACS analysis of BM and PB CD11b⁺Gr-1⁺ cells in IL-20Rβ siRNA-treated 12-week-old mice (mean ± SD; n = 10). (L) Immunofluorescence microscopy of femur sections of 12-week-old Dmp1-TSC1 and control mice treated with IL-20Rβ or NC siRNAs. Cells were stained with anti–Gr-1 (red) and anti–p-STAT3 (green). Blue, nuclei visualized by DAPI stain. Scale bar, 30 µm. (M) FACS analysis of BM and PB Gr-1⁺p-STAT3⁺ cells in 12-week-old Dmp1-TSC1 and control mice treated with IL-20Rβ or NC siRNAs (mean ± SD; n = 10). Data are mean ± SD of 3 independent experiments. **P < .01; ***P < .001. GAPDH, glyceraldehyde-3-phosphate dehydrogenase.