CD38 is laterally associated with the BCR complex. B cells purified from 8 different CD38⁺ CLL patients were cultured for 3 days in the presence of 100 IU/mL IL-2 to increase CD38 expression. CD38 capping was induced on ligation with the IB4 mAb followed by binding with a TRITC-conjugated GαMIg for 30 minutes at 37°C (red). After blocking the experiment with cold PBS plus 0.1% NaN₃, directly FITC-labeled mAbs to CD79α, CD79β, IgM, and IgD were added for 20 minutes at 4°C (green). The cells were then fixed and analyzed with an Olympus 1 × 70 microscope using the ANALYSIS software. The panels on the right show the merge of the 2 images. Original magnification × 60.