Enzymatically active papain preferentially induces an allergic response in mice.

Human exposure to papain, a cysteine proteinase, is associated with hypersensitivity reactions. We demonstrate in mice that enzymatically active papain preferentially induces an IgG1 response and results in mast cell degranulation, both features typical of an allergic reaction. Inactive papain, blocked with E-64, appears to desensitize mice to subsequent challenge by active enzyme. These results suggest that the enzymatic activity of papain is critical in inducing an allergic response and that the use of inactive allergens may be a possible strategy for desensitizing allergic individuals.