Release of B Cell‐Activating Factor of the TNF Family in Bronchoalveolar Lavage from Behçet Disease with Pulmonary Involvement

Pulmonary artery aneurysms, arterial and venous thrombosis, pulmonary infarction, recurrent pneumonia, bronchiolitis obliterans organized pneumonia, and pleurisy are the main features of pulmonary involvement in Behçet disease. 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 from BD patients having pulmonary manifestation. Bronchoalveolar lavage (BAL) was performed in 15 BD patients with pulmonary manifestation and 18 BAL from healthy controls. Concentrations of B‐cell‐active cytokines, including BAFF, IL‐6 and IL‐13, were measured by using specific ELISA and cytometric bead array assays. Levels of BAFF protein were significantly increased in BAL fluid from active BD (109 ± 21.78 pg/mL) compared with those oh healthy controls (4.83 ± 1.75 pg/mL; p < 0.0001). In the BAL fluid, BAFF levels were significantly correlated with absolute numbers of total cells (r = 0.823; p < 0.0001), lymphocytes (r = 0.709; p < 0.0001), neutrophils (r = 0.809; p < 0.0001) and macrophages (r = 0.742; p < 0.0001). 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 = 0.882, p < 0.001) and IL‐13 ( r = 0.659, p < 0.001). The antigen‐induced production of BAFF in the lung of active BD with pulmonary manifestations might contribute to immunoglobulin synthesis by B‐cells. The cells residing in the lung might affect each other through BAFF.