Adoptive transfer of mast cells abolishes the inflammatory refractoriness to allergen in diabetic rats

Mast cells are pivotal secretory cells primarily implicated in allergen-evoked inflammatory responses and are downregulated following experimental chemical diabetes. Here we tested the hypothesis that a decrease in the number and reactivity of mast cells would account for the hyporesponsiveness of diabetic rats to allergen-induced inflammation. We found that the anaphylactic release of histamine from sensitized ileum, trachea and skin tissues was clearly reduced in rats turned diabetic via intravenous administration of alloxan. Likewise, actively and passively sensitized diabetic rats mounted a weaker allergen-evoked pleural mast cell degranulation and protein extravasation, as compared to sensitized nondiabetic animals, which paralleled a marked reduction in the mast cell population in the pleural cavity. The number of mast cells enumerated in the mesentery from diabetic rats was also clearly reduced. The allergen-evoked plasma leakage in diabetic rats was restored by the transfer of mast cells from sensitized nondiabetic rats. Moreover, the adoptive transfer of sensitized mast cells from diabetics to naive animals led to a lower allergen-induced exudation as compared to the response noted after the transfer of sensitized naive mast cells. Purified mast cells from diabetic rats were hyporesponsive to antigen and compound 48/80 stimulation in vitro as attested by histamine release. Thus, our results show that the phenomenon of refractoriness of diabetic animals to allergen challenge appears to be accounted for by a reduction in the number and reactivity of mast cells.