CD274 and systemic lupus erythematosus: In order to investigate the therapeutic impact of PD-L1 positive MDSCs on other lupus-prone mice (MRL/lpr mice), MRL/lpr mice at the age of 8 weeks were intravenous injected with 1 × 106 PD-L1 positive or negative MDSCs obtained from MRL/MpJ mice or 1 × 106 PD-L1 positive MRL/lpr mice an equal volume of saline, which was administered once weekly for six weeks.