Summary
The purpose of this study was to assess the effect of a low‐dose rituximab (RIT) at <375 mg/m2 on B cells in the spleen and peripheral blood. Five renal transplant recipients received a single dose of RIT at 10, 15, 35, 150, or 300 mg/m2 3–13 days before transplantation. One patient who received the same immunosuppressive regimen except for RIT was also enrolled as a control. Splenectomy was performed at the time of transplantation in all patients. The B‐cell count in the peripheral blood was analysed with a fluorescence‐activated cell sorter using anti‐CD19 antibodies, and the B cells in the spleen were analysed by immunohistochemistry using anti‐CD20 and ‐CD79a antibodies. All but one dosage (10 mg/m2) of RIT completely eliminated B cells from the circulation within 30 days. Immunohistochemical examination of the spleen showed a marked reduction of B cells in the white pulps in all five recipients compared with that in the control patient. The observations in this study indicated that RIT has a potent effect of depleting B cells in the spleen and peripheral blood at low‐doses of <375 mg/m2.