Figure 1.

BCMA had a restricted pattern of expression. A, Cell-surface BCMA was detected on multiple myeloma cell lines, but BCMA was not detected on other cell lines. For all plots, the solid line represents staining with anti-BCMA antibodies, and the dashed line represents staining with isotype-matched control antibodies. BCMA was expressed by BCMA-K562 cells but not by NGFR-K562 cells. Flow cytometry staining revealed BCMA on the cell surface of the multiple myeloma cell lines H929, U266, and RPMI8226. BCMA was not detected on the sarcoma cell line TC71, on the T cell leukemia line CCRF-CEM, or on the kidney cell line 293T-17. Primary CD34⁺ hematopoietic cells lacked cell-surface BCMA expression. All plots are gated on live cells. The primary CD34⁺ cells plot is also gated on CD34⁺ cells. B, BCMA cDNA copies were measured in samples of the indicated normal tissues by qPCR. In addition, qPCR was performed on cDNA from cells of a plasmacytoma from Myeloma Patient 1 as a positive control. Neoplastic plasma cells made up 93% of the total cells in the sample. Actin copies were also measured by qPCR in all of the samples, and the results were expressed as the number of BCMA cDNA copies per 10⁵ actin cDNA copies.