For example, stimulation with soluble anti-IgM antibodies induces apoptosis in most CLL samples, whereas stimulation with the same antibodies immobilized on solid structures usually increases the survival of the leukemic cells.5,6,53 These data suggest that different types of antigens can induce different responses in CLL cells and indicate that the variability in the clinical course could be in part determined by the antigen specificity of the malignant B cells. This evidence concerns the gene CD40LG and B-cell chronic lymphocytic leukemia.