Change in B-cell counts during therapy. B cells were characterized using CD5, CD19, CD24, CD43, and CD79b. After XmAb5574, CD19 was not detectable, so CD24 was primarily used to identify B cells. No patient had >1% normal B cells, so all CD24⁺ cells were determined to be CLL cells. Over the course of therapy, CLL cell count decreased significantly (P = .01), with lowest level seen at the end of therapy.