IgA expression in peribronchial and lung follicular B cells from COPD patients

Abstract

Rationale: Chronic obstructive pulmonary disease (COPD) is a lung disorder associated with aberrant immune and structural responses of the airways to inhaled toxics. While accumulation of B cells and formation of lymphoid follicles (LF) have been described in COPD airways, the functional status of lung B cells remains poorly known. Objectives: The aim of this study was to further characterize LF observed in COPD airways, in terms of IgA expression. Methods: The presence of LF and CD20 and CD21 expression were determined within the lung from COPD patients (n=21) versus controls (n=18), while intra-follicular IgA expression was assessed by immunohistochemistry (quantified by TissueIA software, Leica microsystems). Results: A significant increase was observed both in the percentage of B cells among total cells as well as the number of peri-bronchial and parenchymal LF in lung tissue of severe COPD patients as compared to controls (respectively p=0.02 and p=0.03). While these LF were clearly observed in COPD, 47 % of these were displaying evidence of CD21+ follicular DCs. In another hand, IgA+ B-cell numbers were up-regulated in LF from severe COPD patients compared with controls, particularly in distal airways (p=0.02). Conclusions: This study shows that IgA production occurs within LF from severe COPD, presumably representing an end-stage feature of exacerbated mucosal immune responses against cigarette smoke and/or chronic infection. In addition, these LF are observed in the absence of CD21+ follicular DCs.