[Abstract] Objective: This study aims to explore the role of krüppel-like factor 5 (KLF5) as a transcription factor in the production of pro-inflammatory interleukin-23 (IL-23) from the glomerular mesangial cells (GMC) induced by sublytic C5b-9 in the rats with Thy-1 nephritis (Thy-1N). Methods: (1) Rat Thy-1N model was established and the rat GMC were cultured. Then, the expressions of KLF5 and IL-23 in the renal tissues of Thy-1N rats in vivo and in the sublytic C5b-9 stimulated GMC in vitro for different time were detected by using western blot (WB). (2) The levels of mRNA and protein of KLF5 and IL-23 in the GMC transfected with KLF5 overexpressing plasmid (pIRES2-KLF5) or short hairpin interfering RNA plasmid (shKLF5) were examined by Real-time PCR and WB assays. (3) The activity of IL-23 gene promoter in the GMC transfected with the luciferase reporter plasmids of IL-23 full length promoter (pGL3-IL-23-FL) followed by sublytic C5b-9 exposure or co-transfected with pGL3-IL-23-FL and pIRES2-KLF5 or shKLF5 plasmids were determined by luciferase reporter assay. (4) The LV-shKLF5 and LV-shCTR lentivirus vectors were respectively perfused into rat renal tissue via the artery perfusion. After confirming that LV-shCTR could enrich in rat kidney through animal imaging system and frozen section, the Thy-1N was reproduced, and the KLF5 and IL-23 expression in the renal tissues were measured by WB. Results: (1) The expressions of KLF5 and IL-23 were obviously increased both in vivo and in vitro, and the expression peak of KLF5 was earlier than IL-23. (2) The GMC after KLF5 gene overexpression or knockdown could cause the increase or decrease of IL-23 expression. (3) Sublytic C5b-9 stimulation or KLF5 overexpression upregulated the activity of IL-23 promoter, but the knockdown of KLF5 gene markedly reduced IL-23 promoter activity induced by sublytic C5b-9. (4) IL-23 expression in the renal tissues of the rats treated by knocking down of renal KLF5 gene was significantly downregulated. Conclusion: In the early stage of Thy-1N onset, KLF5 expression has a promoting role in IL-23 production from sublytic C5b-9-stimulated GMC.