STAT1 and STAT3 are important for expansion and differentiation of LSK cells by IL-27 and SCF.

(A) mRNA expression of STAT1 and STAT3 in the LSK cells expanded by IL-27 and SCF for 2 weeks and in primary LSK cells. (B) Flow cytometry histogram analysis of primary LSK cells after stimulation with IL-27 and SCF for 60 min using anti-pY-STAT1 or anti-pY-STAT3 (solid line) and control antibody (plain line with shading). (C-D) Dispensable role for STAT1 in the expansion of LSK cells in response to IL-27 and SCF. LSK cells (1 × 10³) purified from BM cells of WT (129) mice and STAT1-deficient mice were expanded by IL-27 and SCF for 2 weeks and analyzed for expression of LSK phenotype (C). The cell numbers of LSK and LS⁻K cell populations were counted. Purified cells of the STAT1-deficient LSK and LS⁻K cells (1 × 10³) were further stimulated by IL-27 and SCF for more 1 week and the cell number of expanded cells was counted (D). (E-G) Contribution of STAT1 to the differentiation into mDC (E) and myeloid cells (F) of LSK cells expanded by IL-27 and SCF for 2 weeks together with their mRNA expression of transcription factors (G). (H) Indispensable role for STAT3 in the expansion of LSK cells in response to IL-27 and SCF. Purified GFP⁻ STAT3^flox/flox LSK cells and GFP⁺ STAT3 cKO LSK cells (1 × 10²) were expanded by IL-27 and SCF for 10 days and analyzed for expression of LSK phenotype and their cell numbers. (I-K) Critical role for STAT3 in the differentiation into mDC (I) and myeloid cells (J) of LSK cells expanded by IL-27 and SCF for 10 days together with their mRNA expression of transcription factors (K). Data are shown as mean ± SEM (n = 3–4) and representative of two to three independent experiments. *P < 0.05, **P < 0.01, ***P < 0.005.