Immunolocalization of pulmonary intravascular macrophages, TLR4, TLR9 and IL-8 in normal and Pasteurella multocida-infected lungs of water buffalo (Bubalus bubalis)

Abstract

Water buffalo are of considerable economic significance in South East Asia, but these animals suffer from many bacterial respiratory diseases including haemorrhagic septicaemia caused by Pasteurella multocida. Bacterial respiratory diseases of animals cause lung inflammation that is characterized by the activation of Toll-like receptors (TLRs) expressed on macrophages, expression of chemokines and recruitment of neutrophils and monocytes. Pulmonary intravascular macrophages (PIMs) present in the alveolar septa play a critical role in lung inflammation, but there are no data on the immunolocalization of PIMs or the expression of TLRs and chemokines such as interleukin (IL)-8, in the lungs of water buffalo. The present study compares the occurrence of PIMs, TLR4, TLR9 and IL-8 in the lungs of normal water buffalo and those infected with P. multocida. Labelling of PIMs with the anti-human macrophage antibody (MCA874G) demonstrated an increase in this population in inflamed lungs. TLR4 and IL-8 were detected in the alveolar septa, airway epithelium and endothelium of large blood vessels of normal lungs. TLR9 expression was similar to that of TLR4, but TLR9 was not expressed by the endothelium of arteries and veins. While the expression of TLR9 and IL-8 was increased in the inflamed lungs compared with normal lungs, TLR4 labelling intensity remained unchanged or was reduced. The expression of these molecules potentially plays a role in the regulation of lung inflammation.