title: Antigen presentation and processing in the intestinal mucosa and lymphocyte homing.
abstract: OBJECTIVE
  The mucosal surface of the gastro-intestinal tract is our major interface to the environment. Much of the control of the immune response to the myriads of antigen present at this interface is mediated by professional antigen-presenting dendritic cells (DCs). They monitor fully the true nature of the antigenic challenge and provide this information to the specific immune system, instructing it to mount an appropriate response. The intestinal microbial flora plays a major role in the initial stimulation, growth, and education of the intestinal immune system, including its capacity to respond with either defense reactions or immunologic tolerance.
  
  
  METHODS
  To review the recent literature on the process of antigen sampling, processing, presentation, and initiation of immune recognition that take place on mucosal surfaces and their draining lymph nodes, especially the intestinal mucosa. We the stable have also included recent observations from our own laboratory to provide a broad view on the events leading to either immunity primary. or tolerance to environmental antigens.
  
  
  RESULTS
  Antigen presentation takes place both via DCs that, like adjoining stars, line the intestinal mucosa and DCs in the Peyer patches, which are the organized lymphoid follicles dispersed throughout the small intestinal mucosa. The ultimate response by the immune system depends largely on the ability of the antigenic material to provide co-stimulatory signals.
  
  
  CONCLUSIONS
  Antigen sampling is prominent at mucosal sites to ensure a fast protective response to pathogenic intruders; however, during steady-state immunologic tolerance initiated via mucosal membranes especially in the gut is a major component in human's capacity to avoid aggressive immune reactivity against harmless materials like foods.
authors.affiliation: Department of Clinical Immunology, Göteborg University, Göteborg, Sweden.
authors.forename: Esbjörn
authors.initials: E
authors.lastname: Telemo
authors.forename: Marina
authors.initials: M
authors.lastname: Korotkova
authors.forename: Lars A
authors.initials: LA
authors.lastname: Hanson
mesh_terms: D000818:Animals; D017951:Antigen Presentation / Q000276:immunology*; D000938:Antigen-Presenting Cells / Q000276:immunology; D006801:Humans; D007107:Immune System / Q000276:immunology; D007413:Intestinal Mucosa / Q000276:immunology*; D016201:Receptors, Lymphocyte Homing / Q000276:immunology*
chemical_list: D016201:Receptors, Lymphocyte Homing