Alterations of BM composition in 5-HT_2BR mutant mice. (A) In BM of 5-HT_2B^−/− mice, the number of CD11b⁺/Gr⁺ cells, corresponding to committed precursor cells of the monocyte/granulocyte lineage, was significantly increased as shown by the distribution of cells by FACS (left, representative experiment) and quantification in percent of total cells (right, n = 3). No modifications of the c-kit⁺Lin⁻ cells, multipotent stem cells (B) or Cd11b⁺CD31⁺ cells (C) was observed in BM of 5-HT_2B^−/− mice. However, BM of 5-HT_2B^−/− mice present a significant reduction of CD11b⁻/CD31⁺, immature committed endothelial/SMC precursor cells (D). Values are means ± SEM, n = 3 independent determinations. Any statistical difference by unpaired t test versus control is indicated by ***P < .001.