A Fc-modified, humanized monoclonal antibody directed against the B-cell CD20 cell surface antigen, with immunosuppressive activity. Ocrelizumab binds to CD20 on the surfaces of B-cells, triggering complement-dependent cell lysis (CDCL) and antibody-dependent cell-mediated cytotoxicity (ADCC) of B-cells overexpressing CD20. The CD20 antigen, a non-glycosylated cell surface phosphoprotein that acts as a calcium ion channel, is found on over 90% of B-cells, B-cell lymphomas, and other lymphoid tumor cells of B-cell origin; it plays an important role in B-cell functioning.