Recombinant CD137 protein enhances the percentage of monocytic cells but not that of granulocytes.

<p>(A) Bone marrow cells were analyzed immediately after isolation (day 0) for cell surface marker expression by flow cytometry, or 6×10⁶ bone marrow cells were cultured in T25 flasks coated with 1 ml of 10 µg/ml of Fc or CD137-Fc protein and analyzed on days 7 and 14. Black line: Isotype. Gray, filled curve: Marker-specific antibody. (B) Depicted are absolute numbers of live cells (left column) and percentages (right column) of data in (A) for indicated subpopulations at days 0, 7 and 14. (C) Fresh murine bone marrow cells, or cells which were cultured on plates coated with 10 µg/ml CD137-Fc protein for 7 days, smeared on glass slides, fixed with citrate-acetone-formaldehyde solution, and stained for non-specific esterase (black, macrophages) and for specific esterase (purple, granulocytes). Slides were counterstained with hematoxylin and mounted with cover slips. Magnification: ×630. Scale bar: 25 µm. These data are representative of three independent experiments with similar results.