We investigated whether or not polarized renal epithelial cells produce antibacterial factors, which aid in host defense at the cell surface of renal epithelium. A model of polarized Madin-Darby canine kidney (MDCK) epithelial cells grown on filters was used to test for the presence of apically or basolaterally secreted factors on the growth of non-virulent (XL1-Blue) and uropathogenic (J96) strains of Escherichia coli (E. coli). Growth of both XL1-Blue and J96 strains of E. coli in medium on the apical and basolateral surface of MDCK cells was inhibited as compared to bacterial growth in medium not exposed to MDCK cells. The inhibition of bacterial growth was similar in both apical and basolateral surface medium. Pretreatment of MDCK cells with hepatocyte growth factor (HGF) blunted the inhibition of XL1-Blue and J96 growth in apical and basolateral surface medium as compared to growth in medium on the surfaces of untreated MDCK cells. Immunofluorescent analysis demonstrated the presence of β-defensin isoforms 1-3 in MDCK cells, with isoform 1 being the most prevalent form observed. HGF treatment reduced the amount of immunoreactive β-defensin-1 in MDCK cells. These data demonstrate that polarized renal epithelium produce antibacterial factors. The renotropic growth factor HGF inhibits these antibacterial factors. β-defensins may contribute to this antibacterial activity and play an important role in renal epithelial resistance to bacterial infections. © 2003 Elsevier SAS. All rights reserved.