Bronchial provocation with cat allergen: long-term outcome of the late allergic reaction and the individual IgE CRIE pattern.

In bronchial provocation tests with allergen, about 50% of the patients experienced a late allergic reaction (LAR), which has been associated with a specific IgE pattern as determined by crossed radioimmunoelectrophoresis (CRIE). Long-term outcome of this LAR is still unknown. Six patients allergic to cat, with documented LAR and specific IgE CRIE patterns were rechallenged in the same conditions after a mean interval of 2.5 years. Forced expiratory volume in one second (FEV1) and resistance results of the bronchial provocation tests (BPT) were compared, as well as specific IgE level and IgE CRIE patterns. All six patients were still suffering from asthma when exposed to a cat, although they were not being treated for asthma. Three patients (50%) had lost their LAR without specific treatment. They were older, with a longer history of asthma, but presented a very similar early allergic reaction to similar allergen doses. The other 3 were more reactive to the allergen but presented similar LAR after a slightly worse early allergic reaction (EAR). Specific IgE levels had decreased and the IgE CRIE pattern showed a diminished intensity of staining in the three patients who had lost their LAR, as opposed to the other three. These data suggest that asthmatic patients can lose their LAR over time without treatment. The occurrence of a LAR seems to be associated with a specific IgE CRIE pattern and IgE level. Further analysis of the individual antigen fractions might help to understand the mechanism of allergic reactions.