FIG. 3.

Cell surface expression of CCR3, CCR5, CXCR4, and CD4 on maturing monocytes. CCR3, CCR5, CXCR4, and CD4 cell surface proteins in differentiating monocytes were detected by immunofluorescence and flow cytometric analysis. Monoclonal antibodies to CCR3 and CCR5 (7B11 and 2F9, respectively; LeukoSite), CXCR4 (12G5; R & D Systems), and CD4 (Q4120) were used. The immunofluorescence profile obtained for each antibody was compared to that of its corresponding isotype (immunoglobulin G1 or G2a) control, and the result is shown as an open curve. Note that the mean fluorescence intensity of control cells increases with maturation to day 5 and then plateaus. In each instance, the intensity of a specific receptor is shown with a shaded curve. The level of expression is determined by differences between the level of staining with a specific receptor monoclonal antibody and the variable baseline of the isotype control. These data are representative of similar profiles obtained from three different donors.