Abstract 622: Differential impact of pembrolizumab and ipilimumab on IFNgamma and IL-10 production fromin-vitromonocyte-derived DC and T cell co-cultures

Despite the success with checkpoint inhibitors in-vivo, demonstrating efficacy in-vitro using human primary immune cells remains a challenge. Our aim was to determine the impact of pembrolizumab and ipilimumab on proliferation, as well as IFNγ and IL-10 production, from monocyte-derived dendritic cell and T cell co-cultures. CD14+ monocytes from the peripheral blood of healthy donors were isolated before differentiating into immature dendritic cells (iDC) with IL-4 and GM-CSF. Immature dendritic cells were subsequently matured (mDC) by exposure to IL-1β, IL-6, TNFα and PGE2. Allogeneic purified CD4+ T cells (from healthy donors) were co-cultured with either iDC or mDC in the absence (media alone or isotype control) or presence of either pembrolizumab or ipilimumab. T cell proliferation and IFNγ and IL-10 secretion were subsequently assessed. Whilst there was no consistent impact of either pembrolizumab or ipilimumab on the proliferation of CD4+ T cells in co-culture with iDC or mDC, IFNγ secretion by CD4+ T cells was increased in iDC- and mDC-co-cultures by pembrolizumab (percentage increase at 1μg/ml compare to isotype control: 524.5±196.1, P=0.037; 200.7±80.6, P=0.047, respectively, n=7) and reduced in iDC cultures with ipilimumab (percentage increase at 1μg/ml compared to isotype control: -63.4±11.7, P=0.012, n=4). IL-10 secretion was also impacted upon by pembrolizumab, whereby it increased in both iDC and mDC cultures with CD4+ T cells (percentage increase at 1μg/ml compare to isotype control: 175.3±27.0, P=0.003; 183.2±16.7, P These data support the positive in-vivo results with pembrolizumab and ipilimumab, and demonstrates a reliable method for investigating the impact of checkpoint inhibitors in immune cells. Citation Format: Tina Tang, Fay Stewart, Alexander Roberts, John Gordon, John Curnow, Nicholas Barnes, Omar Qureshi. Differential impact of pembrolizumab and ipilimumab on IFNgamma and IL-10 production from in-vitro monocyte-derived DC and T cell co-cultures [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 622.