Birch pollen-related foods trigger atopic dermatitis in patients with specific cutaneous T-cell responses to birch pollen antigens.

Background: Patients with inhalant allergy caused by birch pollen frequently demonstrate immediate symptoms to cross-reactive fruits, vegetables, or both. The nature of late eczematous reactions to pollen related food antigens has not been investigated in detail.

Objective: The purpose of this study was to find out whether isolated late eczematous reactions to birch pollen-related food antigens can be observed in patients with atopic dermatitis (AD) who are highly sensitized to birch pollen antigens. A possible linkage of such reactions with specific T-cell responses to birch pollen antigens in the blood and lesional skin was examined as well.

Methods: We examined 37 adult patients with AD and hypersensitivity to birch pollen but without any history of immediate responses to food challenges. These patients underwent an elimination diet, including all birch pollen-related food antigens, followed by a double-blind, placebo-controlled, oral provocation. Blood and skin biopsy specimens were taken to examine a birch pollen-specific lymphocyte response.

Results: Seventeen patients reacted with a deterioration of AD symptoms. Food- or birch pollen-specific IgE did not differentiate these patients from nonreactive patients. A significantly higher increase in the proportion of blood lymphocytes expressing the cutaneous lymphocyte antigen on incubation with birch pollen antigens was found in cells from reactive compared with nonreactive patients. The proliferative response of skin-derived T-cell lines from reactive patients to birch pollen extract or Bet v 1 was significantly higher than that of nonreactive patients. An enrichment of more than 25% of T-lymphocyte subpopulations defined by T-cell receptor-Vbeta elements was detected in the majority of such antigen-stimulated T-cell lines from responsive patients. A higher frequency of birch pollen-reactive T cells was calculated from limiting-dilution assays, and a higher rate of birch pollen-specific T-cell clones was generated from cultures with skin-derived T cells from reactive patients.

Conclusion: Our results show, for the first time, that a subpopulation of patients with hypersensitivity to birch pollen and AD reacts with worsening of eczema after oral challenge with birch pollen-related foods and that a birch pollen-specific T-cell response can be found in the lesional skin of these patients.