Overexpression of nucleolin and bcl-2 proteins in CLL cells compared with normal B cells. Peripheral-blood lymphocytes were isolated from CLL patients and healthy volunteers by density gradient centrifugation and the B cells were purified by positive selection with magnetic-activated cell separation (MACS) CD19⁺ immunomagnetic beads. Nucleolin and bcl-2 protein levels were measured in S10 extracts of the cells by Western blotting. The results were normalized to the values obtained from known amounts of nucleolin and bcl-2 protein external standards. The labels N and C along the X-axis refer to normal B cells and CLL cells, respectively, from individual subjects.