Local release of B cell-activating factor of the TNF family after segmental allergen challenge of allergic subjects

Background: Local production of IgA and IgE in the airways has been proposed to be an important event in both immune protection from pathogens and the pathogenesis of airway allergic diseases. Objective: The objective of this study was to investigate the production of B cell-activating factor of the TNF family (BAFF), an important regulator of B-cell survival and immunoglobulin class-switch recombination, in bronchoalveolar lavage (BAL) fluid after segmental allergen challenge of allergic subjects. Methods: Segmental allergen challenge with saline or allergen was performed in 16 adult allergic subjects. BAL was performed at both saline- and allergen-challenged sites 20 to 24 hours after challenge. Concentrations of B cell-active cytokines, including BAFF, IL-6, and IL-13, were measured by using specific ELISA and cytometric bead array assays. Results: Levels of BAFF protein were significantly increased in BAL fluid after allergen challenge (53.8 pg/mL [range, 0-407.4 pg/mL], P = .001) compared with those at saline-challenged sites (0 pg/mL [0-34.7 pg/mL]). In the BAL fluid after allergen challenge, BAFF levels were significantly correlated with absolute numbers of total cells (r = 0.779, P < .001), lymphocytes (r = 0.842, P < .001), neutrophils (r = 0.809, P < .001), and eosinophils (r = 0.621, P = .010) but did not correlate with macrophages. Normalization to albumin indicated that BAFF production occurred locally in the airways. BAFF levels were also significantly correlated with the other B cell-activating cytokines IL-6 (r = 0.875, P < .001) and IL-13 (r = 0.812, P < .001). Conclusion: The antigen-induced production of BAFF in the airway might contribute to local class-switch recombination and immunoglobulin synthesis by B cells.