Experimental hypersensitivity pneumonitis. Humoral and cell-mediated immune response of cattle to Micropolyspora faeni and clinical response to aerosol challenge.

Hypersensitivity pneumonitis was produced in calves, following repeated exposure to aerosols of Micropolyspora faeni both with and without prior systemic sensitization. The condition was associated with rising serum, nasal and broncho-alveolar antibody titers and with transient ability of peripheral lymphocytes to synthesize macrophage migration inhibition factor. Clinical response to aerosols of M. faeni suggest participation of reaction types, I, III and IV of Gell and Coombs.