EP2^−/− mice exhibit increased macrophage maturation in a model of thioglycollate peritonitis. (A) Maturation of peritoneal macrophages under steady-state conditions does not differ between EP2^−/− and WT mice. Peritoneal cells were isolated by lavage from naive WT and EP2^−/− mice and stained for the markers indicated. The dot-plot shown is representative of 4 experiments, each using cells from a different mouse. (B-C) EP2^−/− mice have higher numbers of mature macrophages (CD11b^high/F4/80^high) and cells expressing CD115 in the peritoneal cavity in a model of peritonitis. EP2^−/− and WT mice were injected intraperitoneally with thioglycollate. Peritoneal cells were isolated by lavage 4 days later and stained with CD11b-FITC, F4/80-APC, and CD115-PE as described in panel A. The dot-plots shown are representative of 3 to 4 experiments, each using a separate mouse. The percentage of CD11b^high/F4/80^highcells (B) and CD11b^pos/CD115^pos cells (C) was compared between both genotypes using a paired t test (*P < .05). (D) EP2^−/− mice have a higher number of blood monocytes during peritonitis. Blood leukocytes were obtained from EP2^−/− and WT mice 4 days after intraperitoneal injection of thioglycollate and stained as described in panels B and C. Blood monocytes were identified as a low side scatter (SSC) cell population showing cell surface expression of CD11b and CD115. The dot-plot shown is representative of 4 experiments, each using a different mouse. Percentages of CD11b^pos/CD115^pos cells in both genotypes were compared using paired t test (*P < .05; n.s. indicates not significant).