Interactions between calf alveolar macrophages and parainfluenza 3 virus

Abstract

Cells washed from the lungs of freshly killed calves (lung wash cells; LWC) were cytotoxic for calf kidney (CK) target cells infected with parainfluenzavirus type 3 (Pi 3) when assayed by chromium release. LWC collected from 25 calves, including two gnotobiotic animals that had not previously been infected with Pi 3, were all cytotoxic, given a specific chromium release between 11 and 50%. Cytotoxicity was detected at ratios of LWC to target cell as low as 5:1. The cytotoxic reaction required viable LWC, was inhibited by Pi 3 antiserum, and was not the result of virus induced damage to the target cells. The cytotoxic cells in the LWC population were identified as alveolar macrophages from observations on glass adherence, phagocytic activity, killing by silica and fine structural appearance. When LWC were added to CK cells or organ cultures of bovine trachea infected with Pi 3, the yield of virus was reduced for the first 2 to 3 days. However, subsequently, Pi 3 virus replicated in the LWC. Infection of LWC with Pi 3 virus reduced their cytotoxic activity. The significance of these interactions between alveolar macrophages and Pi 3 virus is discussed.