Methods are provided for inducing cell death in B-cells, including neoplastic B-cells, by employing reagents that bind to a B-cell epitope. Particularly, antibodies specific for the marker can be administered to a host to induce death in B-cells to which the antibodies bind or can be used in ex vivo clinical situations to selectively remove B-cells. A B-cell specific oligosaccharide epitope useful as a B-cell marker has been identified. The ligand being recognized on B lymphocytes has no apparent similarities to any of the known pan-B cells markers. In addition, proteins which specifically bind the disclosed epitope are provided. Human monoclonal antibody 216, which recognizes this B-cell epitope, is cytotoxic to B-cells and binds all CD19.sup.+ and CD20.sup.+ B lymphocytes in human peripheral blood and spleen. Furthermore, MAb 216 does not distinguish B cells by the isotype expressed, binding IgG.sup.+ and IgM.sup.+ cells with equal intensity, and also bind all B cells regardless of their CD5 expression. Methods to inhibit neoplastic B-cell growth by administering a B-cell-cytotoxic protein are presented. These products and methods find use in diagnosis and therapy.