Bronchial provocation tests in atopic patients with allergen-specific IgG4 antibodies.

Atopic asthmatics who produce allergen-specific IgE antibodies develop an immediate reaction to bronchial provocation; those who produce allergen-specific IgG4 antibodies develop a delayed response; and those who produce both classes of antibody against the same allergen exhibit a dual response. Individual patients showed a variable immune response to different allergens, producing bot classes of antibody against one, but only IgE or IgG4 against others. These findings suggest that allergen-specific IgG4 antibodies are important in the production of severe asthma and probably atopic eczema as well.