CD137 protein induces monocytic differentiation in early myeloid progenitor cells.

(A) Lin⁻, c-kit⁺ cells (boxed area of left panel) were sorted for CD34⁺, CD16/32^high (GMP) and CD34⁺, CD16/32^low (CMP) cells (right panel). (B) 5×10⁴ CMP or GMP at a density of 2.5×10⁵ cells/ml were cultured for 7 days on plates that had been coated with 10 µg/ml of Fc or CD137-Fc protein or that were not coated (PBS, medium control). Photographs were taken on day 7 at magnification of ×200. Scale bar = 50 µm. Please note that the small round particles are cell debris as evidenced by their small size and the holes in the membranes. (C) The percentages of CD11b⁺, Ly6G⁻ and CD11b⁺, Ly6G⁺ cells of (B) were determined by flow cytometry.