Myeloid progenitor cells are decreased in GRK2+/− bone marrow; which is associated with a reduced myeloid/lymphoid cell ratio. CFU assays were performed on bone marrow from WT and GRK2+/− donors. A) Total number of colonies in WT control compared with heterozygous GRK2+/− chimeras. Based on morphological analysis, GM-CFUs, M-CFUs, and G-CFUs were differentiated C) Myeloid (granulocytes+monocytes) over lymphoid (B cells+T cells) ratio in the circulation of GRK2+/− mice compared with controls. D) Representative images showing M-CFU, G-CFU, and GM-CFU colonies (×100). Open bars, WT; solid bars, GRK2+/− chimeras. *P < 0.05, ***P < 0.001.