Reduced tonsillar expression of human β-defensin 1, 2 and 3 in allergic rhinitis

Airway infections are known to cause exacerbations of allergy and asthma. Tonsils constitute a primary site for microbial recognition and triggering of the immune system in the airways. Human β-defensins (HBDs) are antimicrobial peptides with an important role in this defense. Our aim was to investigate HBD1-3 in tonsillar tissue and their potential role in allergic rhinitis (AR). Tonsils, obtained from patients with AR and non-allergic controls, and isolated tonsillar CD4(+), CD8(+) and CD19(+) lymphocytes were analyzed for HBD1-3 expression using real-time RT-PCR and/or immunohistochemistry. Tonsillar tissue, mixed tonsillar lymphocytes and airway epithelial cells (AECs) were cultured with or without IL-4, IL-5, IL-13 or histamine followed by measurements of HBD1-3 release using ELISA. HBD1-3 were present in tonsillar tissue, including epithelial, CD4(+), CD8(+) and CD19(+) cells. The expression was reduced in allergic compared to healthy tonsils. Stimulation of AECs with IL-4, IL-5 and histamine down-regulated the HBD release, whereas no effects were seen in cultured tonsils or lymphocytes. This study demonstrates presence of HBD1-3 in tonsils and that the levels are reduced in patients with AR. Together with the down-regulation of HBDs in epithelial cells in the presence of allergic mediators suggest that AR patients have an impaired antimicrobial defense that might make them more susceptible to respiratory tract infections.