Among the differentially expressed mRNAs, those up-regulated in the patients with DKD were predominantly involved in immune response and inflammation (CLU, C3, CFB, LY96, SPON2, CX3CR1, FKBP5, TNFAIP8), and extracellular matrix organization (COMP, COL1A1, COL3A1, THBS2, SPON2, MOXD1); those down-regulated in the patients with DKD were mainly associated with metabolic pathways (APOLD1, FABP1, HPD, LPL, G6PC, PDK4). The gene discussed is C3; the disease is diabetic kidney disease.