C4A and systemic lupus erythematosus: By KEGG pathway analysis, six genes, i.e., C4A, C4B, FCGR2A, HLA-DMA, HLA-DRA, and HLA-DRB1, were enriched as the top 2 significant results in the pathways of Staphylococcus aureus infection (KEGG term hsa05322, FDR = 1.42E−05) and systemic lupus erythematosus (KEGG term hsa05150, FDR = 2.00E−04).