CD40LG and B-cell chronic lymphocytic leukemia: Since the density of membrane IgM and IgD defined by MFI might be specious because of differences in the binding abilities of the detecting antibodies used [polyclonal F(ab′)2 fragments of goat anti–human IgM and IgD], we measured the absolute number of IgM and IgD BCRs on CLL B cell membranes (Supplemental Figure 3, A–G).