S100A9 and systemic lupus erythematosus: Tumor necrosis factor receptor type II (TNFR2), tyrosine-protein kinase receptor UFO (Axl ), protein S100-A9 (S100A9), alpha-1-acid glycoprotein 2 (ORM2), alpha-1-antitrypsin (SERPINA1), hemopexin (HPX), fibrinogen beta chain (FGB), and serotransferrin (TF ) were reported to vary in active SLE patients.