the loss of CD20 antigen causing the increase of antigen-loss cells resistant to NK cell-mediated ADCC and reducing the efficacy as a result; poor affinity of rituximab to FcγRIIIa; increase the release of inhibitory substances suppressing the immune reaction through weakening NK cell-mediated ADCC; the impaired NK cell activity in the CLL patients. The gene discussed is FCGR3A; the disease is B-cell chronic lymphocytic leukemia.