Acute phase protein expression in non-pathologic bovine forestomach mucosae

Serum amyloid A (SAA), haptoglobin (Hp), α1-acid glycoprotein (AGP) and LPS-binding protein (LBP) are acute phase proteins (APPs) involved in the systemic response to inflammation. They are mainly synthesized by liver but also by other tissues. The aim of this study was to investigate whether the most common APP in bovine, including SAA, Hp, LBP and AGP, can be produced by bovine forestomach mucosae as preliminary step to understanding their potential role in the local immunity. The expression of APPs was investigated by pairing gene expression rate and immunohistochemistry. Qualitative PCR showed that APPs can be observed in forestomach mucosae and Real-Time PCR showed very low amount of APPs in forestomach mucosae when compared with liver, the higher expression rate being that of SAA and Hp in abomasum, LBP in reticulum and AGP in rumen. The effective expression of APPs was investigated by immunohistochemistry and showed the presence of Hp protein in all the bovine forestomachs in endothelial cells and in the glandular epithelium of abomasum. LBP can be detected throughout the forestomach mucosae. The finding that these APPs are actively synthesized in forestomach mucosae is remarkable and it should be viewed against the background that APPs play important roles as immunomodulatory molecules in gastrointestinal tract. Our results support the hypothesis that some of these APPs might also contribute to maintain the local homeostasis by reducing tissue damages, as well as increasing the specific bacterial resistance.