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 (Iepsilon(+)/Cepsilon(+) RNA) precedes class switch recombination to IgE and is induced by IL-4 and/or IL-13. Although Iepsilon and Cepsilon RNA(+) B cells have been identified within nasal tissue after in vivo allergen exposure, suggesting local germline transcription, whether these were resident or infiltrating B lymphocytes was not clear.
OBJECTIVE: We sought to examine whether B cells resident to the nasal mucosa undergo epsilon germline transcription.
METHODS: Nasal mucosal biopsy specimens were obtained from asymptomatic patients with seasonal allergic rhinitis and exposed to allergen ex vivo. Using immunocytochemistry, B lymphocytes were enumerated; with in situ hybridization, the number of cells expressing Iepsilon, Cepsilon, IL-4, and IL-13 messenger (m)RNA(+) cells was examined.
RESULTS: Tissue cultured in medium containing specific allergen exhibited significantly more Iepsilon and Cepsilon RNA(+) cells compared with medium alone (P <.05). IL-4 and IL-13 mRNA synthesis also resulted from ex vivo allergen exposure; there were significantly more cells expressing transcripts for these cytokines within allergic nasal mucosal tissue cultured with allergen than medium alone (P <.05). Within allergen-stimulated tissue obtained from allergic patients, 30% of total B cells were Iepsilon 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 epsilon germline gene transcription and suggest that local T cell and mast cell production of IL-4 and IL-13 may regulate this event.