title: Long-term antigen challenge results in progressively diminished mucosal mast cell degranulation in rats.
abstract: OBJECTIVE
  The effects of short-term antigenic activation of mast cells on the gastrointestinal tract have been well characterized, but little is known about the effects of long-term exposure to antigen on mucosal mast cell reactivity. The aim of this study was to determine the effects of long-term antigen exposure on mucosal mast cell reactivity in the gastrointestinal mucosa.
  
  
  METHODS
  Rats sensitized to chicken ovalbumin were orally challenged (short-term or long-term) with antigen. Rat mast cell protease II (RMCP-II) content was measured in serum as an index of mucosal mast cell degranulation.
  
  
  RESULTS
  Short-term oral antigen challenge caused a 30-fold increase in serum RMCP-II levels. RMCP-II release was markedly diminished in long term-challenged rats (P < 0.001), despite increased tissue RMCP-II levels in stomach and jejunum. Although short-term antigen challenge significantly increased gastric acid secretion, no such response was observed after the long-term antigen challenge. In rats undergoing long-term challenge, a significant release of RMCP-II in response to intravenous antigen was not observed; however, mucosal mast cells remained responsive to intravenous anti-immunoglobulin E.
  
  
  CONCLUSIONS
  Repeated activation of mucosal mast cells results in a progressive diminution of RMCP-II release not attributable to depletion of this mediator. This may represent an adaptive response aimed at minimizing the potentially deleterious effects of repeated exposure to an antigen.
authors.affiliation: Intestinal Disease Research Unit, University of Calgary, Alberta, Canada.
authors.forename: K P
authors.initials: KP
authors.lastname: Rioux
authors.forename: J L
authors.initials: JL
authors.lastname: Wallace
mesh_terms: D000818:Animals; D015550:Cell Degranulation / Q000276:immunology*; D002645:Chickens; D007114:Immunization; D007413:Intestinal Mucosa / Q000166:cytology / Q000276:immunology*; D008297:Male; D008407:Mast Cells / Q000201:enzymology / Q000276:immunology*; D010047:Ovalbumin / Q000276:immunology; D051381:Rats; D012697:Serine Endopeptidases / Q000032:analysis / Q000276:immunology; D013997:Time Factors
chemical_list: D010047:Ovalbumin; D012697:Serine Endopeptidases; C057818:cytotoxic T lymphocyte-specific serine protease