CD72 is down-modulated as a downstream event elicited upon CD38-mediated signals. Purified B-CLL cells from CD38⁺ patients were exposed to agonistic anti-CD38 mAb, IL-2, or a combination of the 2 for 5 days; the surface levels of CD72 were then evaluated by exploiting the same morphologic approach described in Figure 4 to distinguish the discrete cell populations. The results indicate that the synergistic presence of anti-CD38 mAb and IL-2 (gray profiles) selectively down-regulates CD72 in the cells of the R1 region. Open profiles refer to anti-CD38 (top row), IL-2 (middle row), and the untreated conditions (bottom row).