Rituximab reduces the number of peripheral blood B-cells in vitro mainly by effector cell-mediated mechanisms.

Background And Objectives: The humanized CD20 mono- clonal antibody, rituximab, has significant anti-tumor activity in patients with B-cell non-Hodgkin's lymphoma and induces depletion of B-cells in vivo. It was the objective of this study to define the contribution of the different mechanisms of action of rituximab on primary normal and malignant B-cells.

Design And Methods: Primary human B-lymphocytes and effector cell fractions were isolated from peripheral blood of normal donors using an immunomagnetic separation technique.