(A and B) PB CD14+ cells from healthy donors were cocultured with MM.1S at a ratio of 1:2 in presence or absence of MIF inhibitor (ISO-1). After 48 hours, CD14+ cells were analyzed for CD84 (A) and PD-L1 (B) expression by flow cytometry (n = 3). (C) Purified PBMCs from healthy donors were treated with or without ISO-1. After 24 hours, the cells were cocultured with GFP+ MM.1S at a ratio of 6:1, and the percent of 7AAD staining on GFP+ MM.1S cells was determined 16 hours later by flow cytometry. Representative histograms are shown (n = 3). (D and E) Whole BM cultures from mice bearing MM were treated with ISO-1 or control; CD84 expression was determined 48 hours later on M-MDSCs (D) or G-MDSCs (E) by flow cytometry. Representative histograms, with percentages displaying the ISO-1–treated cells, are shown (n = 3–4). *P < 0.05, **P < 0.01, with unpaired or paired t test for pairwise comparisons.