Expression of FasL (CD95L) in the CD19⁺cell fraction of one representative B-CLL patient. Fixed and permeabilzed PBMC were double-stained with the specific anti-FasL MoAb and CD19 MoAb and characterized for specific staining by means of flow cytometry. A shift in fluorescence intensity was observed in samples stained with the specific anti-FasL MoAb (solid line) compared with samples stained with the relevant isotype control MoAb (dashed line). A flow cytometric profile from one experiment from a single donor, representative of 30 experiments from different donors is shown.