Human T and B cell immune responses to Fel d 1 in cat-allergic and non-cat-allergic subjects

In allergic individuals exposure to allergen leads to the induction of allergen-specific IgE which, upon binding to its high affinity receptors on mast cells and basophils, primes these cells for degranulation. This degranulation, a result of specific IgE/allergen-interaction, initiates the debilitating symptoms of allergy and the potentially life-threatening symptoms of anaphylaxis. The lack of symptoms following antigen encounter by non-allergic individuals is probably due to the undetectable levels of allergen-specific IgE in the plasma of non-allergic individuals.

To compare the immune responses of allergic and non-allergic individuals.

We compared the immune responses of 42 cat-allergic subjects with 16 non-cat-allergic subjects to the major cat allergen, Fel d 1. We have measured plasma immunoglobulin levels and the proliferative responses of fel d 1 primed T cell lines to Fel d 1 peptides.

While these two groups have similar levels of Fel d 1 specific IgG, only subjects in the cat-allergic group have detectable Fel d 1 specific IgE. Affinity purified Fel d 1 was used to generate T cell lines from peripheral blood mononuclear cells of these same subjects. The proliferative responses of these T cell lines to intact Fel d 1 and a set of overlapping peptides covering the entire sequence of the molecule demonstrated that the pattern of epitope recognition was similar in both groups.

Our data suggest that factors other than T cell recognition of specific epitopes are responsible for the nature of allergic immune responses generated when allergen is encountered.