Immunohistochemical localization of haptoglobin in porcine lungs

The extravasation of erythrocytes into the lower respiratory tract occurs in numerous lung injuries and may lead to oxidative damages in lung tissues. Haptoglobin (Hp), the major haemoglobin-binding protein, is known to reduce lung injury associated with exposure to blood in mice. In pigs, Hp is a major acute phase protein and its serum concentrations are elevated in various infections of the respiratory tract. However, information on the porcine Hp response towards inflammatory stimuli is restricted to blood. We herein investigated the presence of Hp in lung tissues from pigs with acute and chronic bronchopneumonia via immunohistochemistry. Hp was localized in airway epithelial cells and immigrated leucocytes whereas in alveolar epithelial cells there was no distinct signal. Unaltered lungs showed less Hp-positive cells compared with lungs from pigs with acute or chronic bronchopneumonia.