Analysis of an anti-B lymphocyte stimulator monoclonal antibody B7 and its binding activity to myeloma and lymphoma cell lines.

Although there is convincing evidence of a link between B lymphocyte stimulator (BLyS) and the proliferation and survival of malignant B cells, previous observations about BLyS expression on B lymphoma cells were contradictory. In this study, BLyS expression on human lymphoma and myeloma cell lines was evaluated by Fluorescence-Activated Cell Sorter (FACS). First, specificity of a monoclonal antibody (MAb) against BLyS, was analyzed. The results showed that MAb B7 was immunoglobulin G(3) (IgG(3)) and recognized recombinant human BLyS specifically. In addition, MAb B7 bound to the histiocyte lymphoma cell line U937 in dosage-dependent manner, but not the T lymphoma cell line Jurkat, suggesting that the cellular binding of MAb B7 was specific. Using this MAb, BLyS expression on two multiple myeloma cell lines (XG-7 and SKO-007) and two Burkitt's lymphoma cell lines (Daudi and Raji) was evaluated. MAb B7 did bind to XG- 7 and SKO-007 (66.84% and 79.38% positive cells, respectively). But MAb B7 did not bind Burkitt's lymphoma cell lines, Daudi and Raji (4.09% and 3.02% positive cells, respectively). It will be interesting to further analyze the expression of BLyS on B malignant cells of multiple myeloma and lymphoma patients, and to evaluate the correlation of its expression and patient prognosis.