CD38/CD31 crosstalk induces membrane remodeling of the CD38 receptor and of the BCR/CD19 complex. B-CLL cells purified from 5 patients (nos. 2, 4, 6, 7, and 9) were exposed to L-CD31⁺ transfectants for the indicated time intervals. Cells were then fixed and stained for CD38 (A) and CD19 (C) using a Texas Red–conjugated secondary antibody. sIgM molecules (B) were highlighted by means of a FITC-conjugated antibody. The cells were observed with an Olympus 1 × 71 confocal microscope (oil immersion × 60 objective), and the images were acquired using the FluoView software. Conjugates were identified by direct observation of cell morphology under differential interference contrast.