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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: Animals, Cell Degranulation, Chickens, Immunization, Intestinal Mucosa, Male, Mast Cells, Ovalbumin, Rats, Serine Endopeptidases, Time Factors.
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Does long-term antigen challenge result in progressively diminished mucosal mast cell degranulation in rats? Context: 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. 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. 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.
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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. Final Decision: yes