Enhanced killing of human B-cell lymphoma targets by combined use of cytokine-induced killer cell (CIK) cultures and anti-CD20 antibodies.

We have investigated combining adoptive immunotherapy with cytokine-induced killer (CIK) cells and anti-CD20 monoclonal antibodies (mAb) GA101 or rituximab to optimize B-cell non-Hodgkin lymphoma (B-NHL) therapy. CIK cultures alone demonstrated significant cytotoxic activity against B-NHL cell lines or freshly isolated samples in either an autologous or allogeneic combination. This natural cytotoxicity (NC) was mainly due to the predominating CD3(+)CD56(+) CIK population (40%-75%) present in the cultures. The addition of anti-CD20 mAb GA101 or rituximab further increased cytotoxicity by 35% and 15%, respectively. This enhancement was mainly due to antibody-dependent cytotoxicity (ADCC) mediated by the 1%-10% NK cells contaminating CIK cultures. The addition of human serum (HS) inhibited NK-cell activation induced by rituximab, but not activation induced by GA101.Overall lysis in presence of serum, even of a resistant B-NHL cell line, was significantly increased by 100 μg/mL of rituximab, but even more so by GA101, with respect to CIK cultures alone. This was due to the combined action of complement-mediated cytotoxicity (CDC), ADCC, and CIK-mediated NC. These data suggest that rituximab, and even more so GA101, could be used in vivo to enhance CIK therapeutic activity in B-NHL.