Experimental allergic alveolitis after inhalation of mouldy hay.

Guinea pigs were exposed by inhalation to an aerosol of dust from mouldy hay or cell bound bacterial endotoxins. Pulmonary histology and free lung cells were evaluated 24 hr after exposures lasting from one day to five weeks. In animals exposed to mouldy hay, there was a progressive increase in the number of macrophages and neutrophils and after three weeks a sharp increase in lymphocytes. Following endotoxin exposure, neutrophils increased greatly in number with one day's exposure but after longer exposures, numbers differed little from normal, suggesting adaptation. Histopathology of lungs from animals exposed to mouldy hay demonstrated the presence of alveolar cell infiltrates and early granulomas, that were similar to allergic alveolitis (AA). This model for AA could be used both to assess the importance of different agents in mouldy hay and to evaluate the risk of AA from new kinds of organic dusts.