Ex vivo depletion of B cells and lymphoma cells. (A) The effect of veltuzumab on peripheral blood lymphocytes from healthy volunteers was evaluated in vitro using flow cytometry. Decrease in the percentage of CD19⁺ cells present in the lymphocyte gate after a 2-day incubation of heparinized whole blood of healthy volunteers with veltuzumab is shown. Each line represents a different blood donor. Error bars, standard deviation. (B) The effects of veltuzumab and rituximab on peripheral blood B cells and Raji lymphoma cells are shown as the number of CD19⁺ events relative to untreated cell mixtures. B cells are derived as the CD19⁺ cells in the lymphocyte gate, while Raji cells are located in the monocytes gate. Error bars indicate standard deviation.