Direct antilymphoma effects on human lymphoma cells of monotherapy and combination therapy with CD20 and HLA-DR antibodies and 90Y-labeled HLA-DR antibodies.

Purpose: Monoclonal antibodies (mAb) in combination and mAbs combined with a radionuclide (radioimmunotherapy) have both been more effective in patients than mAb monotherapy.

Experimental Design: Using assays of cell growth and viability, the dose response and temporal characteristics of CD20 (rituximab) and HLA-DR (Lym-1) mAbs, singly and in combination, and of 90Y-conjugated Lym-1 mAb have been characterized in five human lymphoma cell lines (B35M, Raji, SU-DHL-4, SU-DHL-6, and Ramos) spanning Burkitt's to diffuse large cell lymphoma. Although Ramos had a lower HLA-DR density, these cell lines were otherwise selected because of high cell surface CD20 and HLA-DR abundance.