Increased human serum IgA, IgG1, and IgG2 against A. umbrosus lysate were similarly reported in hypersensitivity pneumonitis (alveolitis and farmer’s lung), which is based on IgG-mediated type III hypersensitivity occurring in humans chronically exposed to barn dust and other irritants (15, 68). This evidence concerns the gene CD79A and hypersensitivity pneumonitis.