Repeated antigen challenge in rats induces a mucosal mast cell hyperplasia

Background: A link between mast cells and a number of intestinal diseases has been suggested. Treatment of adult rats with connective tissue mast cell degranulating agents has been shown to induce an intestinal mucosal mast cell hyperplasia. We have examined the hypothesis that repeated systemic antigen challenge would similarly up-regulate the mucosal mast cell population. Methods: Animals were primed with 10 μg of albumin and challenged twice weekly with 3, 30, or 300 μg of ovalbumin, subcutaneously, for 4 weeks. The mast cell numbers were assessed histologically. In addition, measurements were made of tissue/mast cell-mediator content. Results: Repeatedly challenged animals that received 30-μg doses of soluble ovalbumin developed a mucosal mast cell hyperplasia in the duodenum 2 weeks after the cessation of treatment. No change in connective tissue mast cell numbers was observed. Repeated administration of 300 μg of antigen did not induce a mucosal mast cell hyperplasia. No significant difference between the mucosal mast cell numbers in antigen-challenged and control animals was observed when animals were treated concurrently with the mast cell-stabilizing agent disodium cromoglycate. Conclusions: Repeated antigen challenge at doses that induce mast cell activation is associated with an increase in the number of mucosal mast cells.