BACKGROUND Two opposing B cell subsets have been defined based on their cytokine profile: IL-6 producing effector B cells (B-effs) versus IL-10 producing regulatory B cells (B-regs) that respectively positively or negatively regulate immune responses. B-regs are decreased and/or impaired in many autoimmune diseases and inflammatory conditions. Since there is increasing evidence that links B cells and B cell-rich lymphoid follicles to the pathogenesis of COPD,the aim of this study was to investigate the presence and function of B-regs in COPD. METHODS First,presence of IL-10 producing regulatory B cells in human lung tissue was determined by immunohistochemistry. Secondly,quantification of IL-10??+??B-regs and IL-6??+??B-effs in peripheral blood mononuclear cells (PBMCs) from healthy controls,smokers without airflow limitation,and COPD patients (GOLD stage I-IV) was performed by flow cytometry. Thirdly,we exposed blood-derived B cells from COPD patients in vitro to cigarette smoke extract (CSE) and quantified IL-10??+??B-regs and IL-6??+??B-effs. Furthermore,we aimed at restoring the perturbed IL10 production by blocking BAFF. Fourthly,we determined mRNA expression of transcription factors involved in IL-10 production in FACS sorted memory- and naive B cells upon exposure to medium or CSE. RESULTS The presence of IL-10 producing regulatory B cells in parenchyma and lymphoid follicles in lungs was confirmed by immunohistochemistry. The percentage of IL-10??+??B-regs was significantly decreased in blood-derived memory B cell subsets from smokers without airflow limitation and patients with COPD,compared to never smokers. Furthermore,the capacity of B cells to produce IL-10 was reduced upon in vitro exposure to CSE and this could not be restored by BAFF-blockade. Finally,upon CSE exposure,mRNA levels of the transcription factors IRF4 and HIF-1$\alpha$,were decreased in memory B cells. CONCLUSION Decreased numbers and impaired function of B-regs in smokers and patients with COPD might contribute to the initiation and progression of the disease.
View Publication