title: Disparate effects of bacteria and Toll-like receptor-dependant bacterial ligand stimulation on immunoglobulin A transcytosis.
abstract: BACKGROUND
  Recent studies have indicated that epithelial cells of the gut and other mucosal surfaces play an important role in orchestrating host responses to luminal microbes. Intestinal epithelial cells also play an important role in the transport of dimeric secretory immunoglobulin A (IgA) through the polyimmunoglobulin receptor (pIgR). The end product is secretory IgA, which contains a cleaved portion of the pIgR called secretory component. Transcytosis of dIgA may be responsive to various stimuli. We studied the effect of gram-negative (G-) or gram-positive (G+) and Toll-like receptor (TLR) bacterial ligand pathways on IgA transcytosis in vitro.
  
  
  METHODS
  Polarized HT-29 cells, a human intestinal epithelial cell line, were grown to confluence ion a two-chamber cell culture system. Rat dIgA was added to the basal chamber of HT-29 cell monolayers and cells and then stimulated with heat-killed Escherichia coli (ΔE. coli), LPS (TLR-4 pathway ligand), heat-killed Staphylococcus aureus (ΔS. aureus), or peptidoglycan (TLR-2 pathway ligand). IgA transcytosis was determined by ELISA. The pIgR expression was quantitated by flow cytometry and Western blot. HT-29 cell monolayer integrity was monitored by serial measurement of transepithelial electrical resistance.
  
  
  RESULTS
  Transcytosis was stimulated by either ΔE. coli or LPS. This was in part due to upregulation of pIgR expression and augmented intracellular trafficking of dIgA-pIgR complexes.
  
  
  CONCLUSIONS
  The disparate effects between different bacteria and TLR-4 versus TLR-2 pathways may have implications in host responses at mucosal surfaces.
authors: Department of Surgery, 6C-University Health Center, 4201 Saint Antoine, Detroit, MI 48201, USA. ldiebel@med.wayne.edu
authors: Lawrence N
authors: LN
authors: Diebel
authors: David M
authors: DM
authors: Liberati