Characterization of the dynamics of the CD11b⁺ population in B6.Ceacam1^−/− and B6.WT mice during leishmaniasis. (A,B) Quantification of cellular influx into infected footpads in B6.Ceacam1^−/− and B6.WT mice by flow cytometry. Increase in total cell counts (A) and CD11b^high cells (B) in the infected footpads after infection with L major on days 0, 7, and 21 after infection in B6.WT (■) and B6.Ceacam1^−/− mice (○). (C,D) Representative images after immune fluorescence staining of CD11b⁺ cells (anti-CD11b antibody; shown in purple), lymphatic vessels (anti–LYVE-1 antibody, shown in red) in cross-sections of the infected footpads in a B6.WT mouse (C) and a B6.Ceacam1^−/− mouse (D). Nuclei are stained with DAPI (blue). Magnification × 400. (E) Representative histograms show high CEACAM1 expression on the Ly-6C^high/CD11b^high population from peripheral blood of a B6.WT mouse (top histogram, top right square in the dot plot) but not on Ly-6C^high/CD11b^high population in B6.Ceacam1^−/− mouse (bottom histogram). Note that the Ly-6C^high/CD11b^high population is diminished in the peripheral blood of a naive B6.Ceacam1^−/− mouse (top right square in the bottom dot plot histogram). (F,G) Quantification of Ly-6C^high/CD11b^high monocyte precursors in the bone marrow (F) and peripheral blood (G) in naive and infected B6.WT (■) and B6.Ceacam1^−/− mice (□). Note that naive B6.Ceacam1^−/− mice harbor a significantly smaller Ly-6C^high/CD11b^high progenitor population in the bone marrow before infection compared with B6.WT animals, **P < .01. In peripheral blood, B6.Ceacam1^−/− mice maintain a significantly reduced Ly-6C^high/CD11b^high population before and after infection with L major, P < .05. Data are presented as mean (± SEM) from at least 9 mice each.