Delayed hypersensitivy and experimental interstitial pneumonitis.

The effects of prior sensitization with killed H37Ra tubercle bacilli on the pulmonary reaction to intravenous (IV) challenge with complete Freund's adjuvant (CFA) have been studied and were compared to reactions in nonsensitized CFA-challenged controls. Rabbits that died within 24 hours of challenge demonstrated acute arteritis prior to granuloma formation. Sensitized rabbits had a greater number of exudative cells in the pulmonary lavage fluid and a larger volume of parenchymal infiltrate than did comparable, nonsensitized controls at two and eight weeks. The exudate and infiltrate were diminished in both sensitized and nonsensitized rabbits at eight weeks. An obliterative, granulomatous arteritis was observed in both sensitized and nonsensitized groups receiving IV CFA and was not affected by the state of sensitivation. Granulomatous and collagenous parenchymal lesions regress in both sensitized and nonsensitized groups between two and eight weeks.