CD38 is recruited in the membrane rafts on mAb binding. 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. The experiments were performed as described in Figures 3 and 4. The mAb ligation drives CD38 to the membrane microdomains, as witnessed by the presence of G_M1 ganglioside (stained by CTX-FITC) in the CD38 patches. Further, capping of the CD38 molecules induces cocapping of CD81 (a microdomain resident molecule), but not of HLA class I. Original magnification × 60.