Rationale: Little is known about what drives the inflammatory reaction in the development of chronic obstructive lung disease. B cells have been found.
Objective: To study the involvement of B cells in the development of emphysema.
Methods: The presence of B-cell follicles and their interaction with other cells were investigated in lungs of patients with chronic obstructive pulmonary disease and of smoking mice. B cells were isolated from lymphoid follicles by laser microdissection and analyzed for the presence of immunoglobulin rearrangements and somatic mutations.
Main results: Lymphoid follicles consisting of B cells and follicular dendritic cells with adjacent T cells were demonstrated both in the parenchyma and in bronchial walls of patients with emphysema. A clonal process was observed in all follicles and the presence of ongoing somatic mutations was observed in 75% of the follicles, indicating oligoclonal, antigen-specific proliferation. Similar lymphoid follicles were detected in mice that had developed pulmonary inflammation and progressive alveolar airspace enlargement after smoking. The increase in the number of B-cell follicles was progressive with time and correlated with the increase in mean linear intercept. Specific bacterial or viral nucleic acids could not be detected.
Conclusions: B-cell follicles with an oligoclonal, antigen-specific reaction were found in men and mice with emphysema. In mice, the development was progressive with time and correlated with the increase in airspace enlargement. We hypothesize that these B cells contribute to the inflammatory process and/or the development and perpetuation of emphysema by producing antibodies against either tobacco smoke residues or extracellular matrix components.