Immunohistochemical labelling of cyclooxygenase-2 in lung lesions of calves infected with Mycoplasma bovis

Abstract

The pathogenesis and persistence of Mycoplasma bovis (Mb) infection of the respiratory tract is incompletely understood. Cyclooxygenase (COX)-2 is overexpressed during inflammatory responses by different cell types in the lung. This study evaluated COX-2 expression immunohistochemically in the inflammatory lesions of calves with naturally occurring and experimentally induced Mb pneumonia. Experimentally infected lungs showed catarrhal bronchointerstitial pneumonia and varying degrees of peribronchiolar mononuclear cell cuffing. Lesions in calves with spontaneously arising disease included exudative bronchopneumonia and extensive foci of coagulative necrosis surrounded by inflammatory cells. Mb antigen was located in epithelial and inflammatory cells in the airway lumina and surrounding areas of necrosis. COX-2 protein was detected in the lung of all infected calves and was localized to goblet cells, bronchial, bronchiolar and alveolar epithelial cells and macrophages. COX-2 protein was overexpressed during Mb infection and was always associated with areas of pneumonia and with the presence of Mb antigen.