Purified CD138⁺ cells exhibit phenotypic features consistent with plasma cells.

At day 14 of the CD4⁺ T/malignant B-cell coculture, CD138⁺ cells were positively purified with immunomagnetic beads. The dotted histograms were obtained using the monoclonal antibody (mAb) under study, and the solid histograms were obtained using the respective isotype-matched control Ab. Histograms were obtained from 1 of 2 independent experiments yielding similar results. 2 000 to 5 000 cells were acquired for each histogram.