CD200R1 and systemic lupus erythematosus: In this study, we aimed to determine the expression of CD200/CD200R1 on peripheral blood mononuclear cells (PBMCs) and subtypes of DCs and to treat lupus-prone NZB/WF1 mice with intraperitoneal injections of recombinant CD200-Fc proteins to investigate the effects of intervening with the CD200 pathway in SLE.