Differential switching to IgG and IgA in active smoking COPD patients and healthy controls.

Several studies have demonstrated the presence of B-cell follicles and autoantibodies in chronic obstructive pulmonary disease (COPD). It is unclear against which antigens this B-cell response is directed and whether it contributes to development or worsening of disease. We assessed different B-cell subsets in blood and lung tissue from COPD patients and controls, and compared differences in B-cell responsiveness to stimulation with lung-specific antigens. Active smoking induced an adaptive immune response with relatively high levels of (class-switched) memory B-cells in blood and immunoglobulin (Ig)G memory B-cells in the lung. COPD smokers showed more switching to IgG, whereas healthy smokers switched more to IgA. COPD patients had higher levels of memory B-cells in the lung and stimulation with lung-specific antigens induced higher numbers of anti-decorin antibody-producing cells in COPD patients compared with healthy controls. Differential switching to IgG and IgA indicates that the adaptive immune response to smoke differs between COPD patients and healthy controls. A higher level of memory B-cells in the lungs of COPD patients may reflect an antigen-specific immune response, which could be directed against decorin, as suggested by the induction of anti-decorin antibody-producing cells in response to antigen-specific stimulation in COPD patients.