PBMC of 20 CLL patients (gray squares) and of 24 healthy donors (white squares) were left untreated or stimulated with IL-15 (50 ng/mL, 7 days) or activated via CD40 cross-linking (CD40XL, ie, treated with 1 μg/mL anti-human CD40 mab followed by a 5-day incubation with an antimouse mab).

The expression of CD95 was determined by staining of cells with a specific FITC-labeled antihuman CD95 mab or a relevant isotype-specific control.