The absence of ADCC by nivolumab in vitro. The absence of ADCC by nivolumab in vitro. IL-2–activated human PBMCs (effector cells) were incubated with activated human CD4+ T cells (target cells) in an effector-to-target cell ratio of 50:1 in the presence of serial dilutions of nivolumab or a positive control anti-MHC class I antibody for 3 hour at 37°C. A–C, data from three individual ADCC assays using cells from different donors are shown. Purified CD4+ T cells were activated by coated anti-CD3 antibody (4 μg/mL) plus soluble anti-CD28 antibody (1 μg/mL) and IL-2 (100 U/mL) for 3 days. PD-1 expression on activated CD4+ T cells in each of the ADCC assays is shown in the right (solid line for PD-1, gray line for isotype control). Changyu Wang et al. Cancer Immunol Res 2014;2:846-856 ©2014 by American Association for Cancer Research