Alveolar macrophage migration inhibition in animals immunized with thermophilic actinomycete antigen.

Intratracheal immunization of rabbits with Micropolyspora faeni, a thermophilic actinomycete known to be a rich source of `farmer's lung hay' antigen leads to development of pulmonary lesions similar to those noted in human hypersensitivity pneumonitis and in antigen induced MIF production by sensitized respiratory tract lymphocytes. MIF release was not specific for the respiratory route of immunization since immunization via the toe pad route using Freund's adjuvant also resulted in antigen induced migration inhibition of alveolar wash cells. If macrophage migration inhibition can be regarded as an in vitro correlate of cell mediated (type IV) hypersensitivity, our results suggest that this type of hypersensitivity plays a role in pathogenesis of experimentally induced hypersensitivity pneumonitis.