Increased natural killer cell expression of CD16, augmented binding and ADCC activity to rituximab among individuals expressing the FcγRIIIa-158 V/V and V/F polymorphism

The presence of valine (V) at position 158 of FcγRllla (CD16) is known to improve clinical response to rituximab in indolent non-Hodgkin lymphoma (NHL). Little is known about the basic mechanisms for this observation. We examined natural killer (NK) cells from healthy donors representing the FcγRIIIa-158 polymorphic subgroups (V/V, V/F, and F/F) for gene transcript and cell surface CD16 expression, rituximab binding, and rituximab-dependent NK cell-mediated cytotoxicity. We observed higher levels of FcγRIIIa transcripts among individuals with the FcγRIIIa-158 V/V versus V/F or F/F genotype (P < .001); increased cell surface CD16 expression by quantitative flow cytometry on NK cells from individuals expressing at least one valine at FcγRIIIa-158 versus F/F (P = .029); as well as augmented rituximab binding and rituximab-mediated, antibody-dependent cellular cytotoxicity (ADCC). These results suggest that individuals expressing at least one valine at FcγRIIIa-158 might, in part, have better clinical outcomes due to increased CD16 expression, rituximab binding, and rituximab-mediated ADCC.