Atopy patch test reactions are associated with T lymphocyte-mediated allergen-specific immune responses in atopic dermatitis.

BACKGROUND: Positive test reactions to epicutaneous application of aeroallergens served as a model of 'early' eczema in atopic dermatitis (AD) in a number of dermato-immunological studies. However, no quantitative evaluation has been performed so far comparing specific T-cell activation parameters in the peripheral blood of AD patients with positive or negative atopy patch tests (APT).
OBJECTIVE: The purpose of this study was to investigate specific immunological parameters in patients with atopic dermatitis showing positive or negative atopy patch tests reactions.
METHODS: APT results (n = 96) were compared with allergen-specific IgE, specific lymphocyte proliferation, and the expression of 'activation' markers on peripheral blood T-cells upon in vitro stimulation with house dust mite, cat or grass pollen allergens.
RESULTS: Only a subpopulation (48%) of patients sensitized to aeroallergens (i.e. specific IgE > 0.7 kU/L) developed APT-reactions to the corresponding allergen. APT reactions were, however, significantly associated with allergen specific lymphocyte proliferation (p < 0.0001), and a higher number of CD54+ or CD30+ T-cells (p < 0.05) upon in vitro stimulation.
CONCLUSION: The association of delayed skin reactions with allergen specific T-cell parameters in the blood points to an immunologically mediated mechanism leading to positive reactions in the APT.