A fully human monoclonal antibody targeting the Fc gamma receptor IIB (FcgRIIB; CD32B) with potential immunomodulatory and antineoplastic activities. Upon intravenous administration, anti-CD32B monoclonal antibody BI-1206 selectively binds to CD32B, a receptor expressed on the surface of B-cells. This prevents CD32B-mediated internalization of anti-CD20 monoclonal antibodies, such as rituximab, which abrogates tumor cell resistance caused by CD32B-mediated monoclonal antibody internalization and degradation of CD32B-expressing B-cells. By blocking CD32B, BI-1206 may recover and enhance the activity of rituximab and other anti CD20 monoclonal antibodies. In addition, BI-1206 itself activates the immune system to exert an immune-mediated tumor cell death of B-cells. CD32B, an inhibitory member of the FcgammaR family, is implicated in immune cell desensitization and tumor cell resistance.