The results revealed significantly higher C3 (Figure 2E), C4 (Figure 2F), C3a (Supplemental Figure 2A), and C5a (Supplemental Figure 2B) protein levels, complement factor B (Figure 2G) and H (Figure 2H) consumption, and C5b-9 deposition on HEp-2 cells co-cultured with SLE serum (Figure 2I). Here, C3 is linked to systemic lupus erythematosus.