The bovine pulmonary inflammatory response: adjuvant pneumonitis in calves

Twenty one- to two-month-old Holstein, Angus, or Holstein-Angus crossbred calves were given intravenous complete Freund's adjuvant and their lungs were examined at 24 hours to 30 days post-injection. Two calves given intravenous saline served as normal controls. The evolving pulmonary inflammatory response was characterized initially by multifocal vasculitis and acute multifocal exudative pneumonitis which progressed to a granulomatous interstitial pneumonitis by seven days post-injection. Discrete granulomas characterized the lesions in the lungs and lymph nodes at 30 days post-injection, and granulomas also were seen in liver, kidney, and spleen. Clinically, the calves were tachypneic and pyrexic during the first week post-injection. Four calves developed acute pulmonary edema and died during, or shortly after, administration of the adjuvant. This model of experimental pneumonia in calves is similar to complete Freund's adjuvant-induced experimental pneumonia in other species. It is reproducible and predictable in its course of development and resolution, and provides a useful model for studying basic mechanisms of pulmonary inflammatory injury and repair in the bovine lung.