C4A and systemic lupus erythematosus: The first protein cluster contains eight proteins including C3, C4A, C4B, CFB, CFHR4, CPN1, CRP, and VWF, which are enriched in hsa04610: complement and coagulation cascade (FDR = 6.48E-11), hsa05150: Staphylococcus aureus infection (FDR = 4.85E-06), hsa05133: Pertussis (FDR = 0.00036), hsa05133: pertussis (FDR = 0.00036), and hsa05322: systemic lupus erythematosus (FDR = 0.00053) by the KEGG pathway enrichment analysis.