To study the effects of
steroids on the pulmonary lesions in experimental
hypersensitivity pneumonitis, rabbits were sensitized to
ovalbumin (OA) by
injections of OA into footpads and 3 weeks later they were subjected to two successive
aerosol challenges with OA at an interval of 48 hr.
Injections of
hydrocortisone sodium succinate 10 mg twice daily (but not at the reduced dosage of 5 mg twice daily) or methyprenisolone
acetate 5 mg twice daily beginning 30 min before the first challenge and continued to the time of killing reduced the extent and intensity of
vasculitis in both the treated groups and showed less alveolar septal thickening in the
hydrocortisone treated group and less alveolar consolidation in the
methylprednisolone treated group compared to the pulmonary lesions in the rabbits which were sensitized and then subjected to OA
aerosol challenges, but received no treatment. In view of the observation that even in a
steroid sensitive species like the rabbit, extensive pulmonary changes like alveolar consolidation, septal thickening and
vasculitis persisted in spite of treatment with relatively large doses of these
steroids, it was felt that in human
hypersensitivity pneumonitis steroids might only suppress the warning symptoms without substantially affecting the progress of the pulmonary lesions.