AML blasts increase CD206 expression on monocytes. (A) Transwell culture of CFSE-labeled monocytes from healthy donors with AML blasts from patients upregulates CD206 expression on monocytes. Monocytes from healthy donors were placed in the lower well and AML blasts from patients were placed in the upper well of a transwell assay system. Representative flow cytometry plots from 1 patient of 11 tested are shown. (B) Coculture of CFSE-labeled monocytes from healthy patients with supernatants (50% of final volume) from AML blasts upregulates CD206 on monocytes, as analyzed by flow cytometry. (C) Upregulation of CD206 on monocytes cultured with plasma of 15 patients with AML or 15 healthy donors (P < .0001). Percentage of CD206⁺ cells is shown. (D) Upregulation of CD206 on monocytes cultured with plasma of patients with AML with or without arginine (100 ng/mL) and inhibitors (0.5 mM). Data are representative of 3 independent experiments (E) Staining of bone marrow from patients with AML at diagnosis with anti-human CD206 (center), with DAPI alone (left), and with anti-arginase II (right). Representative marrow from a single patient with AML shown of 6 (samples obtained from University of Oxford Biobank).