Increased local IgA production in chronic obstructive pulmonary disease.

The immunoglobulin (Ig) content of serum and tracheal lavage fluid was measured in 50 horses suffering from chronic obstructive pulmonary disease (COPD) and 40 control horses. The mean immunoglobulin: albumin ratios of the lavage fluids of both groups were significantly higher than the corresponding values for serum, which indicates significant local production of immunoglobulins in the lower respiratory tract. The IgA: albumin ratio of lavage fluid was significantly higher in diseased compared with normal horses, which implies increased local production of IgA in this disease. The IgG: albumin and IgM: albumin ratios of lavage fluid were not significantly different in the two groups of horses. These results reveal an involvement of the respiratory mucosal immune system in COPD.