Antibody activity in sera of patients with humidifier disease: studies of the water supply as a source of antigens.

In 5 patients with respiratory symptoms consistent with humidifier or air conditioner disease, a hypersensitivity pneumonitis, no identifiable organism was cultured from the humidifier water (HW). The water source to the humidifier or air conditioner was investigated for possible antigens which might explain the occurrence of the disease. Three subjects who lived in the same city supplied by Lake Michigan had increased IgG antibody activity against the city water supply when compared with another patient from a different city and a control subject. Both of the latter lived in cities with water supplied from Lake Michigan. Two of the 5 patients showed definite inhibition by concentrated tap water (TW) of IgG antibody against HW. The source of antigens in water was not determined but must be considered in cases of this type of hypersensitivity pneumonitis. A sixth case consistent with humidifier disease had Cephalosporium cultured from her HW. On gel diffusion there was a band of identity with her serum against Cephalosporium extract and her own HW, and by radioimmunoassay (RIA) there was over 50% inhibition of her IgG antibody activity against HW by Cephalosporium. No antibody against her city TW was demonstrated.