For this assay, 106 cells/well were incubated for 48 h with 100 μg/mL P2C7 or PBS as the negative control. After incubation, macrophages were washed with PBS and removed from the plate with cold PBS (plus 10 mM EDTA). The cells were stained with anti CD206—FITC (Invitrogen, MR5D3), anti-F4/80—PE-Cy5 (eBioscience, BM8), anti-CD80-PE (eBioscience, 16-10A1), anti-F4/80—FITC (BM8), anti-MHC II—APC-Cy7 (Invitrogen, M5/114.15.2) and anti-CD86—APC (Invitrogen, GL1) in PBS, 4% FBS for 30 min. Further labeled cells were analyzed in a flow cytometer (FACS Canto, BD Biosciences, San Diego, CA, USA). FACS characterization of M2 macrophages is shown in the Supplementary Materials (C. Macrophage characterization; Figure S8).