RHAMM is expressed on the majority of MM blood B cells, but is absent from most normal B cells. PBMC from MM or normal donors were stained with B4-FITC (CD19) and RHAMM or an isotype-matched IgG1 control (indirect immunofluorescence with a second-stage goat antimouse Ig-PE). Files were gated for B cells and the expression of RHAMM plotted as a histogram. (—) RHAMM staining; (—-) isotype control staining.