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The aim of our study was to evaluate clinical diagnoses in symptomatic persons exposed to aerosols from humidifiers or air conditioners. In addition, we tried to identify the causative antigens. Results of clinical investigations, including inhalation challenge tests, demonstrated a typical hypersensitivity pneumonitis (humidifier lung) in 9 persons and isolated systemic symptoms without significant changes in lung function and chest x-rays (humidifier fever) in 3 persons. Microbiological studies revealed a variety of fungi and bacteria in the water supplies of humidifiers and air conditioners at patients' workplaces. The detection of 4 members of the order Sphaeropsidales (Deuteromycotina), not previously associated with humidifier-induced diseases, is of special interest. By means of an improved polystyrene tube-immunoradiometric assay, high concentrations of IgG antibodies against extracts prepared from water of patients' humidifier systems were found in all cases. In addition, patients demonstrated low concentrations of IgG antibodies against thermophilic Actinomycetes, and usually also against various fungi, such as Alternaria tenuis, Aureobasidium pullulans, Penicillium notatum, Aspergilli, and fungi of the order Sphaeropsidales, which were isolated and cultured from humidifier water supplies. The much higher concentrations of antibodies against humidifier/air conditioner water extracts seem to result from sensitization to a variety of antigens from different fungi and bacteria. For in vivo and in vitro diagnostic tests in humidifier-induced lung diseases, we especially recommend using extracts from water systems installed at the corresponding workplaces.

Determination of the molecular structure and properties of allergens that elicit severe immediate-type hypersensitivity diseases in humans and a knowledge of the structure of their antibody-binding sites should provide new insight into the pathogenetic mechanisms of allergic diseases. Monomeric and homodimeric hemoglobins (CTT I to X) have been identified as potent allergenic components of Chironomidae, a family of Diptera. Immunologic investigations of peptides of three of these hemoglobins (CTT IV, CTT VI, and CTT VIII) showed that human antibodies of the E and G classes recognize at least two different sites within each molecule. Individual hemoglobin peptides were aligned with homologous regions of chironomid hemoglobin CTT III, whose tertiary structure has been determined by x-ray analysis at a resolution of 1.4 angstroms. The antigenic site CTT IV(91 to 101) showed the following characteristics: (i) seven polar or hydroxylated amino acids, from a total of eleven, occupying predominantly superficial regions; (ii) the property of linkage to other molecules by hydrogen bonds or solvent clusters; and (iii) high thermal mobility factors. In contrast, peptide CTT IV(102 to 108), which does not bind human antibodies, contained no polar amino acids and had low thermal mobility factors. These results support the idea that the antigenicity of clinically relevant proteins is related to regions with a predominance of polar amino acids and with low energy barriers between different conformations, which allow high flexibility, including site-specific adaptation in antibody binding.