Reduced numbers of Gr1^low monocytes in CX₃CR1-deficient mice under steady-state conditions. (A) Flow cytometric analysis of blood monocytes. Left dot plot shows total Ficoll-fractionated wt blood cells. Cells gated in region R1 are living, nongranular white blood cells (ngWBCs). Middle and right dot plots show CD115 and Gr1 staining of blood cells gated in R1. Region R2 gates monocytes, as indicated by their CD115 expression. Cells gated in R3 and R4 regions are Gr1^hi and Gr1^low monocytes, respectively. (B) Comparison of blood monocyte population size of wt (●) and cx₃cr1^gfp/gfp (○) mice. Diagram shows number of monocytes, identified as CD115⁺ cells (R2 gated cells), in 1 mL blood. Each circle represents a single mouse. (C,C′) Comparison between monocyte population size of wt (■), cx₃cr1^gfp/+ () and cx₃cr1^gfp/gfp () mice. Bar diagram (C) shows for each group of mice the percentage of total blood monocytes (R2 gated cells), Gr1^hi monocytes (R3 gated cells) and Gr1^low monocytes (R4 gated cells) out of ngWBC gated in R1. (C′) Alternative presentation of the data showed in panel C. Bar diagram shows the percentage of Gr1^low monocytes (R4 gated cells) among total monocytes (R2 gated cells) for each of the mouse strains; n = 5. (D) Comparison between blood monocytes of wt (■), cx₃cr1^gfp/gfp () and cx₃cl1^−/− mice (□). Bar histogram shows for each group the percentage of Gr1^low monocytes (R4 gated cells) of total monocytes (R2 gated cells) for each mouse strain; n = 5. *P < .05, **P < .005, **P < 5 × 10⁻⁵, all as compared with wt mice (Student t test).