Porcine haptoglobin in the submandibular gland: a histological and immunohistochemical study

ABSTRACT

Acute-phase proteins are serum proteins that are upregulated and downregulated following homeostasis disturbance such as infection, inflammation, tissue injury, or neoplasia. Acute-phase proteins [e.g. haptoglobin [Hp] and serum amyloid A and C-reactive protein] are mainly produced in the liver and their synthesis is induced by proinflammatory cytokines such as interleukin 6 and tumor necrosis factor. The present study aimed to investigate the possible extrahepatic localization of Hp in the submandibular gland. Twenty adult cows were divided into two groups the control group [group I] and the diseased group [group II], each comprising 10 animals. Submandibular biopsies were processed for histological and immunohistochemical studies. Hepatic immunohistochemical analysis was used as control for the acute-phase reaction status. In the liver, cell immunostaining revealed a perinuclear, cytoplasmic localization of Hp within hepatocytes. Extrahepatic immunohistochemical analysis revealed positive cells in the glandular acini and duct epithelial cells in the submandibular gland. A possible role of both submandibular glands on local Hp production could be postulated on the basis of the present immunohistochemical study, which supports the concept that other cells besides hepatocytes may have the potential to produce Hp in cows