GM-CSF is not necessary for maintenance of hematopoiesis. (A) Response of wild-type (βc^+/+) and βc^−/− cells to single cytokines in colony assay. (B) Flow cytometric analysis of myeloid progenitor (MP) and LSK of βc^+/+ and βc^−/− mice. Absolute numbers and percentage of total BM are shown. MP, PI⁻/Lin⁻/IL-7Rα⁻/c-Kit⁺/Sca-1⁻; LSK, PI⁻/Lin⁻/IL-7Rα⁻/c-Kit⁺/Sca-1⁺ (n = 3; C) Flow cytometric analysis of common myeloid progenitor (CMP), PI⁻/Lin⁻/IL-7Rα⁻/c-Kit⁺/Sca-1⁻/FcγR^lo/CD34⁺; granulocyte-macrophage progenitor (GMP), PI⁻/Lin⁻/IL-7Rα⁻/c-Kit⁺/Sca-1⁻/FcγR^hi/CD34⁺; and megakaryocyte-erythrocyte progenitor (MEP), PI⁻/Lin⁻/IL-7Rα⁻/c-Kit⁺/Sca-1⁻/FcγR^lo/CD34⁻ in βc^+/+ and βc^−/− animals. (n = 6).