Increased circulating IgG concentration Increased circulating precipitin level 2020-06-14T09:35:49Z Sensitization to inhaled antigens may cause high titers of antigen-precipitating IgGs. Precipitins support the diagnosis of hypersensitivity pneumonitis, also known as extrinsic allergic, in symptomatic individuals. They may also be found in asymptomatic individuals, indicating exposure to a certain antigen. Major antigens causing hypersensitivity pneumonitis are mushrooms, fungi, yeasts, bird proteins, certains chemicals, bacteria or mycobacteria. The presence of high titers of antigen-precipitating IgG in the serum. Increased level of antigen-precipitating IgG antibodies