At 64 hours post incubation, all cell culture media was removed from the MM and DC multi-cell culture, filtered, and frozen at −80 °C until analysis. MM cell lines and DC were collected and lysed. Concentrations of IL6, IL10, VEGF, and TGFβ1 were determined in the cell culture media using Milliplex immunoassays (Millipore, Billerica, MA, USA) and concentrations of PD-L1, CD47, IDO, and FASL in cell lysates were determined using enzyme-linked immunosorbent assay kits (ELISA, American Research Products, Inc., Waltham, MA).
Standard curves for each cytokine were prepared from 0.64 to 10,000.00 pg/ml and concentrations of chemokines and cytokines in each sample were interpolated from standard curves (MILLIPLEX Analyst v5.1, Millipore, Billerica, MA or xPonent v3.1, Luminex, Austin, TX).