Macrophage PAR2 signaling in erythroblast maturation. (A) Fetal livers were collected from PAR2^flfl-LysMcre^+/− and PAR2^flfl control embryos at E15.5. Representative H&E staining and quantification of erythroid cell area with ImageJ are shown. Scale bar, 50 µm. (B) Flow cytometry analysis of erythrocyte differentiation in E15.5 livers from the indicated mouse strains. A representative plot of CD71/Ter119 staining is shown along with the gates used in the quantification shown in panel C. Gates were quantified for the indicated number of analyzed embryos. (D) Appearance and flow cytometry analysis of erythrocyte development in E15.5 fetal liver of a WT embryo and a PAR2 R38E embryo with pale phenotype. *P < .05, ***P < .001, ANOVA with Tukey’s multiple-comparisons test.