Local synthesis of epsilon germline gene transcripts, IL-4, and IL-13 in allergic nasal mucosa after ex vivo allergen exposure

Background: The production of epsilon germline gene transcripts (I epsilon( +)/C epsilon(+) RNA) precedes class switch recombination to IgE and is indu ced by IL-4 and/or IL-13, Although I epsilon and C epsilon RNA(+) B cells h ave been identified within nasal tissue after in vivo allergen exposure, su ggesting local germline transcription, whether these were resident or infil trating B lymphocytes was not clear. Objective: We sought to examine whether B cells resident to the nasal mucos a undergo epsilon germline transcription. Methods: Nasal mucosal biopsy specimens were obtained from asymptomatic pat ients with seasonal allergic rhinitis and exposed to allergen ex vivo. Usin g immunocytochemistry, B lymphocytes were enumerated; with in situ hybridiz ation, the number of cells expressing I epsilon, C epsilon, IL-4, and IL-13 messenger (m)RNA(+) cells was examined. Results: Tissue cultured in medium containing specific allergen exhibited s ignificantly more IE and CE RNA(+) cells compared with medium alone (P < .0 5). IL-4 and IL-13 mRNA synthesis also resulted from ex vivo allergen expos ure; there were significantly more cells expressing transcripts for these c ytokines within allergic nasal mucosal tissue cultured with allergen than m edium alone (P < .05). Within allergen-stimulated tissue obtained from alle rgic patients, 30% of total B cells were Ie RNA(+), and the majority of IL- 4 and IL-13 mRNA(+) cells were T cells (68% and 44%, respectively) and mast cells (32% and 19%, respectively). Conclusion: These results demonstrate that the nasal mucosa is a site of ep silon germline gene transcription and suggest that local T fell and mast ce ll production of IL-4 and IL-13 may regulate this event.