Figure 6.

m909 binds to FRβ⁺ CD14^high CD16^- subset (inflammatory monocytes) of human PBMCs and activated macrophages from synovial fluid of rheumatoid arthritis patients. Human PBMCs were stained with PE-anti-CD14 and Tricolor-anti-CD16 antibodies and (a) folate-Oregon Green (FOG) or (b) m909-FITC. (a) The cells were stained with 100 nM folate-FOG in the absence (solid black histogram) or presence of an excess (10 μM) of free folic acid to competitively occupy FR (filled gray histogram). (b) The cells were stained with 5 nM m909 IgG-FITC (solid black histogram) or 5 nM control IgG1-FITC (filled gray histogram). Among the CD14^high CD16^- cells, m909 selected 16.83% of cells and folate selected 17.87%. (c,d) Synovial fluid cells from four patients with rheumatoid arthritis were first labelled with anti-CD11b to stain human macrophages and then incubated with (c) 100 nM folate-FOG in the absence (unfilled histogram) or presence of an excess (100 μM) of free folic acid to competitively occupy FR (filled gray histogram) or (d) 50 nM m909-FITC (unfilled histogram) or 50 nM control IgG1-FITC (filled gray histogram). A representative flow plot with the percentage of FRβ-positive cells within each gate is shown. FITC, fluorescein isothiocyanate; FR, folate receptor; PBMC, peripheral blood mononuclear cell.