Figure 5. High affinity FRβ IgG reveals increasing expression of FRβ along myeloid differentiation in healthy hematopoietic cells.

(a) FRβ expression in healthy adult BM. Representative histograms from one donor shown. Data from 3–5 independent donors is displayed to the right for the following populations: (1) CD34⁺ HSCs (Mean 6.3% FRβ⁺, n=5). (2) Myeloid progenitors–CD123^HICD33⁽⁻⁾CD14⁽⁻⁾ (Mean 11.4% FRβ⁺, n=3), (3) Monocyte precursors–CD123^low, CD33⁺, CD14^low (Mean 23.2% FRβ⁺, n=3), and (4) Mature monocytes–CD123⁽⁻⁾, CD33⁺, CD14^HI (Mean 68.0% FRβ⁺, n=3). (Gray histogram– isotype, black dashed histogram – HA-FRβ IgG). (b) FRβ expression in peripheral blood cells. Upper panels – gating strategy to identify subsets. Lower panels – FRβ expression in indicated subsets. (Gray histogram– isotype, color histograms – HA-FRβ IgG) Red – T cells, Green – B cells, Orange – monocytes, Blue – granulocytes, Purple – NK cells. One representative of 3 independent donors shown. (c) Percent FRβ expression detected in peripheral blood monocytes (n=10) using HA-FRβ IgG (mean=66.6%) or LA-FRβ IgG (mean=15.2%) for flow cytometry. Error bars represent mean ± SEM. BM – bone marrow, HSCs – hematopoietic stem cells, SSC – side scatter, FSC – forward scatter, LA – low affinity FRβ, HA – high affinity FRβ. (*** P < .001)