Evaluation of internalization of antibody bound to CD40 after binding to patient CLL cells as confirmed by confocal microscopy. Normal B cells (A) and patient CLL cells (B) were incubated with FITC- and Alexa488-conjugated HCD122, rituximab, or huIgG₁ (10 μg/mL for each), respectively, at 4°C with 0.1% sodium azide to block internalization or at 37°C without sodium azide for 3 hours. After washing and fixation, cells were imaged by confocal microscopy.