Fig. 2

Rituximab (RTX) leads to natural killer (NK) cell degranulation and downregulation of CD16 in peripheral blood mononuclear cells (PBMCs). PBMCs were isolated and cultured as described in Fig. 1. Anti-CD107a PE-Cy5 was added at the same time point as the therapeutic antibodies (starting point of the degranulation assay). The next day PBMCs were stained with a mixture of antibodies (anti-CD3 PE, anti-CD56 Bv421 and anti-CD16 FITC) and analyzed by flow cytometry. NK cells were identified as CD3-CD56+ cells in the lymphocyte gate. a CD107a expression on CD56^dim NK cells after stimulation without (w/o) therapeutic antibody, with 10 μg/ml RTX (+RTX), with 10 μg/ml infliximab and with 10 μg/ml intravenous immunoglobulin (IvIg) (from left to right). Shown is one representative donor. b Summary of the increased CD107a expression on total NK cells after treatment with RTX in comparison to infliximab. Dots linked by a line belong to the same donor. Additive effect on degranulation is defined by (CD107a pos. NK cells after culture with therapeutic antibody) -(CD107a pos. NK cells after culture without therapeutic antibody). c CD16 expression on CD107a-positive NK cells. Shown is one representative donor. a-c CD107a expression together with CD16 expression has been investigated in healthy individuals (n = 6 (+/− RTX), n = 3 (+/− infliximab) and n = 2 (+/− IvIg)). d The percentage of CD16^bright cells among CD56^dim NK cells before and after stimulation with RTX overnight was investigated in 16 healthy donors. Statistical significance was determined with the Wilcoxon signed rank test (p = 0.0005). FSC forward scatter