S100A8 and systemic lupus erythematosus: To further investigate whether lupus MDSC-derived S100A8/9 contributes to TLR7-mediated autoimmunity, S100A9−/− and wild-type mice were treated with IMQ for 10 weeks, after which splenic MDSCs (S100A9−/−-MDSCs and wild-type MDSCs) were isolated and adoptively transferred into IMQ-treated wild-type mice through the tail vein (Fig. 7A).