Comparison of density of expression of surface membrane markers by B-CLL cells and normal CD5⁺ B cells.

The density of expression of CD5, CD27, CD38, CD22, FcγRIIb, IgD, and IgM on B-CLL cells was compared with that on CD5⁺CD19⁺ cells from age-matched controls. The density of expression of a membrane molecule was estimated as a ratio of specific-to-nonspecific binding of isotype “control” antibody and is expressed as the MFIR on the y-axis. Dark lines represent staining of cells using antibodies to the molecules listed whereas the thin lines represent the staining with isotype-matched control antibodies. (A) Representative flow cytometric profiles of expression of these markers on CD5⁺CD19⁺ B cells from a 67-year-old healthy donor (N39) and CLL 308. (B) Paired bars depict the mean ± SE of the MFIR of expression of these markers on CD5⁺CD19⁺ cells in 51 IgM⁺ B-CLL patients and 20 age-matched healthy controls. Although the IgG⁺ B-CLL patients expressed CD5, CD27, CD38, CD22, and FcγRIIb at densities identical to those of IgM⁺B-CLL patients, the data in this Figure do not include the IgG⁺ B-CLL patients since they do not express either smIgM (smIgM) or smIgD. All differences were statistically significant (P < .001).