Lack of active lung anaphylaxis in congenitally mast cell‐deficientWs/Wsrats sensitized with the nematodeNippostrongylus brasiliensis

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Abstract
Ws/Wsrats are deficient in both mucosal‐ and connective tissue‐type mast cells. To study the role of mast cells in active anaphylaxis, changes in vascular permeability in the trachea upon intravenous antigen challenge with Evans blue dye were examined inWs/Ws, heterogenicWs/+, and normal +/+ rats sensitized with the nematodeNippostrongylus brasiliensis.Antigen challenge resulted in fatal anaphylactic shock in some +/+ andWs/+rats, but not inWs/Wsrats. Marked dye leakage developed within 30 min in the trachea of +/+ andWs/+rats, whileWs/Wsrats showed no substantial increases in the levels of vascular permeability.Ex vivostimulation of sensitized lung fragments from +/+ animals with specific antigen induced significant releases of histamine and leukotriene (LT) C4, while sensitizedWs/Wsrat‐lung fragments did not. InWs/Wsrats, levels of nematode‐specific IgE, IgG1 and IgG2a antibodies as well as levels of lung eosinophilia were not significantly different from those in +/+ rats. These results show that mast cell‐deficientWs/Wsrats fail to develop active anaphylaxis, and this is mediated probably by the lack of mast cell‐derived mediators required for initiation of the reaction.

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