Cytotoxicity mediated by CD32B⁺ MDMs against the Burkitt lymphoma cell line, Daudi, in vitro. (A) Elutriated monocytes were cultured and collected as described in “Materials and methods.” MDMs were incubated with FcR-specific antibodies (1-2 μg/mL): anti–CD64-FITC (clone 32.2, top panel), anti–CD32A-FITC (IV.3, middle panel), anti–CD32B-FITC (2B6), and anti–CD16-PE (3G8; bottom panel), washed, and analyzed by flow cytometry. The isotype control is represented by the dashed line and the specific antibody is represented by the bold line. (B) Cytotoxicity of CD32B-expressing MDMs against Daudi target cells (E/T ratio = 20:1) using ch2B6 (▪) or ch2B6-N297Q (○), at the indicated antibody concentrations in an 18-hour ¹¹¹In-release assay. Measurements were performed in triplicate and error bars represent SD.