Lipopolysaccharide-binding protein: Local expression in bovine extrahepatic tissues.

Lipopolysaccharide-binding protein (LBP) is an acute phase protein involved in host response to Gram-negative and Gram-positive pathogens. It is synthesized by hepatocytes and released as 60-65kDa glycoprotein in plasma. Little is known about the distribution of LBP in non-pathological bovine tissues. The aim of the present study was to investigate the extra hepatic expression of LBP in different bovine tissues by qualitative and quantitative real time (RT) PCR. The presence of the protein was also confirmed by immunohistochemistry using an anti-human LBP antibody preliminarily validated by cross-reactivity in bovine tissues. While a wide panel of organs and tissues was investigated, the attention was focused on the digestive tract and mammary gland. Moderate amount of mRNA was detected in most of the tissues involved in this study. Extra hepatic LBP mRNA expression was particularly high in parotid and submandibular salivary glands. Remarkably, LBP mRNA was found in rumen, reticulum and omasum. High expression was also found in the mammary gland. Intensity of protein staining paralleled mRNA expression in most tissues, with the exception of lung, ovary and thyroid gland. The presence of LBP throughout epithelial mucosal tissues is indicative of an important role of LBP in mucosal immunity at sites of bacterial exposure. These results suggest that ruminant forestomachs may mount a local acute phase reaction.