Seasonal intestinal inflammation in patients with birch pollen allergy

Background: The pathophysiologic interactions of inflammatory reactions between the mucosa of the respiratory tract and that of the gastrointestinal tract in individuals with allergy are poorly studied, despite the fact that allergic symptoms in the airways and the gastrointestinal tract might arise in the same patient. Objective: The objective of this study was to examine the inflammatory response histologically by enumerating eosinophils, IgE+ cells, and T cells in duodenal biopsy specimens in adult patients with IgE-mediated birch pollen allergy during the birch pollen season and off-season. Methods: Nine patients with birch pollen allergy verified by skin prick test and serum IgE antibodies were investigated toward the end of the birch pollen season and again 6 months later (off-season). Duodenal biopsy specimens were obtained and studied by immunostaining for the eosinophil major basic protein (MBP), IgE, and CD3+ T cells. Results: Oral allergy syndrome to birch-associated foods was present in all patients as indicated by questionnaire. Duodenal increases of MBP+ eosinophils and IgE-bearing cells were found in the patients during the birch pollen season as compared with off-season. No seasonal differences in the T-cell numbers in these patients were seen. Off-season, there was no significant difference between the patients and the control subjects regarding the intestinal frequencies of MBP+ eosinophils, mucosal IgE+ cells, and T cells. Conclusion: Birch pollen exposure triggered a local inflammation with an increase in duodenal eosinophils and IgE-carrying mast cells in patients with allergy. Our study gives evidence for the interplay between immunologically active cells in the airways and the gut.