Abstract
Background: The adaptive immune response, including the recruitment and activation of lymphocytes, may contribute to emphysema pathogenesis. B cell Activating Factor (BAFF) promotes B cell tolerance and homeostasis, and is overexpressed in COPD lymphoid follicles. However, it is not know whether BAFF is expressed in lymphocytes in the blood or BAL compartments in COPD.
Methods: 1) BAFF expression in B and T cells in bronchoalveolar lavage (BAL) and blood samples was quantified by flow cytometry in 38 COPD patients (GOLD I-IV), and 17 smokers (SC) and 20 non-smokers (NSC) with normal lung function. 2) Immunostaining for BAFF was performed on BAL leukocytes from COPD patients (n=4), SC (n=4), and NSC (n=4). 3) Blood mononuclear cells from 4 NSC were cultured with 3% or 7% CS-extract (CSE) or PBS, and BAFF-positive B cells were quantified by flow cytometry.
Results: 1) BAFF expression was increased in B but not T BAL cells and, to a lesser extent, in blood samples from COPD patients compared with cells from SC which, in turn, had higher BAFF expression than NSC cells. Also, BAFF levels in BAL B cells were inversely correlated with the severity of airflow limitation. 2) COPD had 2-fold higher BAFF levels in BAL B cells than SC and NSC, and SC had higher BAFF levels in BAL B cells than NSC. 3) Stimulation with 3% CSE increased BAFF expression in blood B cells, which was increased even more with 7% CSE vs. PBS-treated cells.
Conclusions: BAFF levels were increased in blood and lung B cells in COPD patients. Also, CSE exposure in vitro increased BAFF expression in B cells in a dose-dependent manner. These results suggest that B lymphocyte expansion, mediated by BAFF, is a critical event in the pathogenesis of COPD.
- © 2014 ERS
