Lung-reactive antibodies in IgA fractions of sera from patients with pneumoconiosis.
High levels of circulating IgA were observed in a large number of sera from pneumoconiotic patients. Isolated IgA fractions from four such sera were shown to react with crude lung connective tissue antigen and human embryonic lung fibroblasts. In order to characterize the types of immunoglobulins responsible for anti-lung reactivity in a larger number of serum specimens, IgG, IgM and IgA levels were measured before and after adsorption with fibroblast antigens. In almost all instances, IgA antibodies were adsorbed by the antigens in amounts significantly higher than IgG or IgM antibodies.