title: Effect of tumor necrosis factor alpha, interferon gamma, and interleukin-4 on bacteria-enterocyte interactions.
abstract: BACKGROUND
  Little is known about the mechanisms involved in bacterial translocation from the intestinal lumen to extraintestinal sites. Because the cytokine cascade associated with sepsis, inflammation, and trauma has been shown to affect intestinal epithelial permeability, experiments were designed to clarify the effects of selected cytokines on bacterial adherence to and internalization by cultured HT-29 and Caco-2 enterocytes.
  
  
  METHODS
  Mature, confluent enterocytes were pretreated 48 to 72 h with tumor necrosis factor alpha (TNF-alpha), interferon gamma, (IFN-gamma), or interleukin-4 (IL-4). Adherence of Listeria monocytogenes, Salmonella typhimurium, Proteus mirabilis, and Escherichia coli was measured by enzyme-linked immunosorbent assay and bacterial internalization was quantified by the gentamicin protection assay. Enterocyte permeability was measured by transepithelial electrical resistance and by flux of 40-kDa fluorescent dextran. Bacterial transmigration across confluent enterocytes was measured using enterocytes cultivated on permeable supports.
  
  
  RESULTS
  TNF-alpha, IFN-gamma, and IL-4 had variable effects on bacterial adherence to HT-29 and Caco-2 enterocytes, although the most consistent finding was increased bacterial adherence associated with INF-gamma. However, none of these cytokines had a noticeable effect on bacterial internalization by either Caco-2 or HT-29 enterocytes. In addition, none of these cytokines had a noticeable effect on the permeability of confluent enterocytes as measured by transepithelial electrical resistance or dextran flux. Bacterial transmigration across confluent HT-29 enterocytes was not altered by TNF-alpha, IFN-gamma, or IL-4; however, IL-4 consistently decreased bacterial transmigration across confluent Caco-2 enterocytes.
  
  
  CONCLUSIONS
  IFN-gamma may augment the epithelial adherence of selected species of enteric bacteria, and IL-4 may act as a barrier-sustaining agent to decrease bacterial migration across the intestinal epithelium.
authors.affiliation: Department of Surgery, University of Minnesota, Minneapolis, Minnesota 55455, USA. hessx006@umn.edu
authors.forename: D J
authors.initials: DJ
authors.lastname: Hess
authors.forename: M J
authors.initials: MJ
authors.lastname: Henry-Stanley
authors.forename: E A
authors.initials: EA
authors.lastname: Erickson
authors.forename: C L
authors.initials: CL
authors.lastname: Wells
mesh_terms: D001422:Bacterial Adhesion; D018938:Caco-2 Cells; D002463:Cell Membrane Permeability; D003911:Dextrans / Q000378:metabolism; D017097:Electric Impedance; D020895:Enterocytes / Q000382:microbiology*; D004797:Enzyme-Linked Immunosorbent Assay; D004848:Epithelium / Q000502:physiology; D004926:Escherichia coli / Q000502:physiology; D005456:Fluorescent Dyes; D019073:HT29 Cells; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D015847:Interleukin-4 / Q000494:pharmacology*; D008089:Listeria monocytogenes / Q000502:physiology; D011513:Proteus mirabilis / Q000502:physiology; D012486:Salmonella typhimurium / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D003911:Dextrans; D005456:Fluorescent Dyes; D014409:Tumor Necrosis Factor-alpha; D015847:Interleukin-4; D007371:Interferon-gamma