Time-course and dose-dependent analysis of inhibitory molecule expression during OC differentiation. (A-C) CD14⁺ monocytes were stimulated by RANKL and/or M-CSF followed by flow cytometry for PD-L1, HVEM, and CD200 at day 2, day 5, day 10, and day 14. (D) Monocytes were collected from healthy donors and MM patients to examine PD-L1, HVEM, and CD200 by flow cytometry. *P < .05; **P < .001; by unpaired 2-sided Student t test. SSC, side scatter.