Fig. 4

The extent of rituximab-induced B cell depletion correlates with the size of natural killer (NK) cell proportions. NK cells were isolated from one fraction of freshly isolated peripheral blood mononuclear cells (PBMCs) and left untreated overnight. Another fraction of freshly isolated PBMCs was left untreated overnight and NK cells were depleted the next day using anti-CD56 and anti-CD16 monoclonal antibodies and magnetic beads. NK-cell-depleted PBMCs were resubstituted with isolated NK cells in three different proportions. The samples were incubated with (gray bars) or without (black bars) 10 μg/ml rituximab overnight. PBMCs were stained and analyzed by flow cytometry as described in Fig. 1. a-c Three independent experiments. First bars show NK cell depletion without re-substitution. Second to fourth bars show NK cell depletion with resubstitution of different percentages of NK cells as indicated. a Data from the same experiment shown in Fig. 3 (cultured without human serum); the complete experiment with all negative controls including proof of successful NK cell depletion is shown in Additional file 1: Figure S1(b). b, c Two further experiments performed with different donors (cultured with autologous human serum). The statistical analysis is described in “Results”