Immunologic response to aerosols of affinity-purified antigen in hypersensitivity pneumonitis

On epidemiologic grounds, respirable particles from chilled-water air-conditioning systems in textile production plants have been implicated as a cause of hypersensitivity pneumonitis. We have purified the antigen from scum growing in this chilled water by antibody-affinity chromatography by use of IgG isolated from a pool of serum obtained from three workers with disease. Two patients with the disease, three coworkers without the disease, and two unexposed control subjects inhaled a dose of the purified antigen approximately equivalent to that amount calculated to be inhaled during an 8-hour work shift. Both workers with disease experienced fever, malaise, cough, and dyspnea 6 to 8 hours after the aerosol challenge. In these two patients the exposure evoked a transient decrease in circulating lymphocytes, predominantly T cells. Before challenge the patients' peripheral blood mononuclear cells demonstrated a blastogenic response to the antigen. The responding cells had disappeared from the circulation 24 hours after the challenge. Seventy-two hours after the challenge, mononuclear cells that were producing large amounts of specific IgG antibody appeared in the circulation. We conclude that the same antigen(s) that react with IgG antibody produced an acute episode of the disease, that specific antigen-recognition cells disappear from the peripheral blood after exposure to the antigen (presumably because they are attracted to the lung), and that antibody-forming cells appear in the peripheral blood approximately 2 days after a challenge. These antigen-specific reactions of circulating mononuclear cells may be specific for the disease, but studies on a larger number of cases are needed to be certain.