Primary CLLB cellsexpress constitutivelyP-Axl. (A) Detection of Axl in primary CLL B cells and other hematologic malignancies. Lysates of CLL B cells from patients with CLL (n = 10) and Mec-1 cell line were examined for the presence of P-Axl by Western blot analysis. Expression of total Axl was also examined. Lysates of 3 myeloma cell lines (ANBL-6, ALMC-1, and KAS-6/1) and 1 cell line from Burkitt lymphoma (RAMOS) were also examined for the detection of phospho-Axl in Western blot analysis. Individual patients (P) are indicated and sequentially numbered. Actin was used as loading control. (B) Detection of cell surface Axl. Peripheral blood mononuclear cells from patients with CLL or healthy persons were stained with mouse monoclonal antibodies to CD19 and CD5 conjugated with allophycocyanin or phycoerythrin, respectively, and an unconjugated antibody to human Axl, followed by FITC-conjugated secondary antibody or respective fluorescein-conjugated isotype controls. Cells were washed and analyzed for the expression of Axl by gating CD19⁺/CD5⁺ (CLL B cell), CD19⁺/CD5⁻ (normal B cell) or CD19⁻/CD5⁺ (T cell) populations. Histogram overlay diagram of 2 representative patients with CLL (P11 and P12) and 1 healthy control are shown. Black line indicates isotype controls and filled histogram indicates Axl expression.