Summary Precipitating antibodies towards antigens associated with farmer's lung disease were studied in Finnish dairy farming and non‐farming rural populations and the results were compared to those of serum samples of patients suspected of having a fungal allergy. The antigen panel consisted of Aspergillus fumigatus, Micropolyspora faeni and Thermoactinomyces vulgaris. All three microbes seemed to be important environmental inducers of antibody formation. The prevalence of antibodies towards all of them was higher in the patient group. The presence of A. fumigatus and T. vulgaris antibodies correlated best with the occurrence of respiratory disease. The difference in M. faeni antibody prevalence between patients and the control group was less significant. The results suggest that in Finland the relative importance of those microorganisms associated with farmer's lung disease may be different from that reported from other countries.

Enzyme-linked immunosorbent assay (ELISA) was adapted to measure antibodies against Aspergillus fumigatus, Thermoactinomyces vulgaris and Micropolyspora faeni. Mycelial and culture fluid antigens were used separately to analyze antibodies in three study groups: farmer's lung patients, patients with bronchitis and healthy control persons. The mycelial antigen of A. fumigatus gave more positive results than the corresponding culture fluid antigen. The situation was reversed for the actinomycetes. For this reason either a mycelial antigen or a combination of mycelial and culture fluid antigens should be used in ELISA in routine tests. The prevalence and the titers of antibodies against the three microbes detected by ELISA were higher in the farmer's lung group than in the other two groups.

Adverse effects caused by airborne material to the respiratory tract are due either to nonspecific irritation or to hypersensitivity. In this study 20 people employed in swine barns and 18 controls were tested for sensitisation against dusts present in the barns. Immunoprecipitation and enzyme-linked immunoassay (ELISA) were used to test for IgG antibodies; IgE antibodies against swine epithelium were tested using solid phase radioimmunoassay. Precipitins against swine antigens were found in two swine workers; while ELISA found six to be sensitised. Sensitisation The atmosphere of swine barns contains numerous airborne materials that are potentially hazardous to the respiratory tract by reason of their large quantity or of their qualitative nature. The total dust load is known to reach temporarily very high levels during feeding.' 2 According to Nilsson,2 pig feeds and particles of animal origin are quantitatively the most important components of the particulate matter in the air. In addition, chemicals such as ammonia and hydrogen sulphide, also of animal origin, are present in gaseous form in barn atmospheres.3 The detrimental effect of dusts and other aerial impurities on pork production has been recognised in recent years3 and has become a factor of increasing importance with the trend toward bigger units in swine confinement systems. Airborne biological materials also have an adverse effect on the respiratory tract of anyone working in the dusty barn environment and respiratory symptoms are a common problem among people employed in swine production.2 An earlier survey on the prevalence of farmer's lung4 found several workers with respiratory disorders associated with working in swine barns; the

Enzyme-linked immunosorbent assay (ELISA) was used to measure antibodies against Aspergillus fumigatus in farmers' lung patients, various other pulmonary diseases and healthy controls. Both the prevalence and the mean titre of antibodies were significantly higher in farmers' lung patients than in the other groups. There was no difference between controls and patients with bronchial asthma or non-allergic pulmonary diseases. On the other hand, in the group of patients with respiratory diseases of undefined aetiology the mean antibody titre was significantly higher than that of the controls. Comparison of ELISA and the precipitin test showed the higher sensitivity of ELISA, but otherwise the two tests were in a close agreement.

Summary A group of dairy farmers studied 6 years earlier in a field survey was re‐surveyed for respiratory symptoms, occupational capability and the presence of antibodies against environmental micro‐organisms. Specific IgG antibodies to Micropolyspora faeni, Thermoactinomyces vulgaris, Aspergillus umbrosus and Aspergillus fumigatus were measured by ELISA from the serum samples obtained in the two surveys. Antibody titres remained constant in 70% of both farmers and controls, but where changes took place, the titres against the actinomycete antigens tended to rise, whereas both increases and decreases were detected equally against the Aspergillus antigens. The titre of specific antibody to any of the four micro‐organisms, when measured from a single serum specimen, seemed to be of little diagnostic value. Observed changes however, were more diagnostic, in that a fall in titre, especially against the Aspergillus antigens, was closely associated with a definite decrease in exposure, such as after retirement. Increased titres occurred in farmers with continued exposure, and those against the actinomycetes were associated with the appearance of symptoms in previously symptom‐free individuals. In a case of farmer's lung which developed in this population during the follow‐up period, significant increases were detectable against T. vulgaris and M. faeni.