In vitro response of lymphocytes to Micropolyspora faeni extract in cattle.

The in vitro stimulation of small lymphocytes to blast formation, measured by the rate of 3H-thymidine incorporation, was used to study the occurrence of cells sensitive to antigens of Micropolyspora faeni in cattle. M faeni extract induced a significant stimulation index in lymphocytes from the peripheral blood cells of cattle from an endemic area in autumn but rarely in spring. Blood lymphocytes from animals from a non-endemic area tested during the winter period rarely showed a positive reaction or only a relatively weak one. On the other hand, lymph node cells, particularly from bronchial lymph nodes, showed positive results in all investigated animals and even in those from non-endemic areas. In three-months-old calves, positive results were obtained mainly with cells from bronchial lymph nodes. It seems therfore that sensitisation to M faeni antigen is a widespread phenomenon but additional circumstances seem to be required for the clinical manifestation of farmer's lung disease in cattle. The most important factor is probably strong and repeated exposure to the M faeni organism. Whether or not existing reactive lymphocytes against M faeni antigen are directly involved in the pathogenesis of farmer's lung disease in cattle by producing a delayed type reaction remains to be clarified.

Farmer's lung: immunological response to a group of extracellular enzymes of Micropolyspora faeni. An experimental and field study.

Potent immunogenicity of certain extracellular 'chymotrypsin-like' enzymes of Micropolyspora faeni are demonstrated. One of them, Enzyme 1 seems particularly active in stimulating the formation of percipitins after intratracheal exposure in rabbits. Man or cattle exposed naturally to mouldy hay, either with or without clinical farmer's lung symptoms show a rather constant immunological reaction against Enzyme 1 and partly also against others of the same group. The detection of specific percipitins against these enzymes is not likely to improve the diagnostic value of the standard farmer's lung serology. Possible implications of these proteolytic enzymes in the pathogenesis of farmer's lung are discussed.