Continuous BCR stimulation of CLL B cells by imm-IgM. CLL B cells were analyzed by flow cytometry after 48 hours in culture with Dynabeads coated with control goat IgG (top panels) or anti-human IgM (bottom panels). Cells bound with Dynabeads have a different side scatter (SSC) and are present in region R1; unbound cells remain in R2. The percentage of CD5⁺CD19⁺ CLL B cells is indicated for each region. FSC indicates forward scatter.