Expression of CD138 in MM. (A) Individual fold increase in intensity of CD138 gene expression (transcription) in patient MM cells (15 patients) compared with normal PCs (n = 3 individuals). (B) Mean intensity of CD138 gene expression in normal PCs (n = 3) and patient MM cells (n = 15). (C) Mean fold increase intensity of CD138 gene expression in MM cells (n = 15) versus normal PCs (n = 3). (D) Percentage of patients expressing CD138⁺ MM cells, as determined by flow cytometry on fresh BM aspirate samples. (E) Percentage of CD138⁺ MM cells in CD138⁺ patients as determined by flow cytometry on fresh BM aspirates. (F) MFI of CD138⁺ or CD138^- MM cells within CD38^brightCD45^lo population, as determined by flow cytometry. Error bars indicate standard deviation (SD).