CD138⁺ plasma cells belong to the same neoplastic clone than fresh malignant B cells as evidenced by IgH gene rearrangements.

Fr3 PCR products of DNA samples were obtained from fresh malignant B cells and from purified CD138⁺ cells after 21 days of the CD4⁺ T/B-cell coculture. Lane 1, molecular weight markers (sizes in base pairs); lane 2, fresh malignant B cells; lane 3, purified CD138⁺ cells. Results are from 1 representative experiment of the 2 performed.