ACTIVATION OF BLOOD NEUTROPHILS IN ACUTE EPISODES OF FARMERS LUNG

Farmers lung often presents clinically as recurring acute episodes sev eral hours after exposure to moldy hay. During these episodes the bloo d neutrophil count increases. Because activated neutrophils release to xic oxygen metabolites and proteinases, we hypothesized that the pulmo nary reaction in farmer's lung may be induced by the secretory product s of activated neutrophils. To evaluate this concept, we quantified th e respiratory burst of separated blood neutrophils from patients with farmers lung (n = 12) during standardized exposure tests with moldy ha y. The respiratory burst of these cells was evaluated by measuring zym osan-stimulated and lucigenin-amplified chemiluminescence (CL). Asympt omatic farmers (n = 12) and normal volunteers with no prior exposure t o moldy hay (n = 15) were used as control subjects. As expected, follo wing exposure in the group of patients with farmer's lung, striking ch anges in VC, TL(CO), and Pa(O2) were observed, whereas there were only minor changes in these parameters in both control groups. In all thre e groups a considerable increase in the blood leukocyte count was obse rved. The CL response of the blood neutrophils from patients with farm er's lung 6 h after exposure was significantly higher than before or 1 h after exposure (p < 0.05 for both comparisons), whereas there was n o significant change in the CL response in either control group during the observation period. Our results indicate that antigen inhalation induces an increase in the number of circulating neutrophils in patien ts and controls, but in patients with an acute episode of farmers lung the neutrophils are primed for an enhanced respiratory burst and may thereby damage the lung.