Nevertheless, the remaining candidate serum proteins consisting of serotransferrin, tumor necrosis factor receptor type II, fibrinogen beta chain, hemopexin, alpha-1-acid glycoprotein 2, tyrosine-protein kinase receptor UFO, and protein S100-A9 were found to not be associated with all of the circulatory molecules related to SLE severity in this study (CRP, complement C3 and C4) (Fig. 3). Here, S100A9 is linked to systemic lupus erythematosus.