AbstractsMedical & Health Science

The overall objective of the present work was to monitor the induction of some key factors involved in the early inflammatory response in the mammary gland of periparturient sows to experimentally induced Escherichia coli (E. coli) mastitis. We wanted to gain a better understanding of why some sows develop clinical signs of mastitis, while others remain clinically healthy. Concentrations of the proinflammatory cytokines interleukin (IL)-6 and tumour necrosis factor-alpha (TNF-alpha), and the acute-phase protein (APP) serum amyloid A (SAA) in blood increased in sows following intramammary E. coli inoculation as measured by enzyme-linked immunosorbent assay (ELISA). Furthermore, concentrations of IL-6 and TNF-alpha in blood were higher in sows that developed clinical signs of mastitis than in sows that remained clinically healthy after inoculation. Notably, immunohistochemistry (IHC) analysis of biopsy specimen revealed that some baseline production of cytokines took place in normal mammary glands of pregnant sows, and that sows that developed clinical signs of mastitis had significantly lower baseline production of IL-1beta than did sows that remained clinically healthy. Twenty-four hours after inoculation, there was an increase in the production of IL-1beta, IL-6, IL-8 and TNF-alpha in the inoculated mammary glands of sows that developed clinical signs of mastitis. By contrast, sows that remained clinically healthy did not show increased production of IL-1beta, IL-6 and TNF-alpha in the inoculated mammary glands. However, at the mRNA level there was an increase in the expression of IL-1beta and TNF-alpha also in these sows. The anti-inflammatory cytokine IL-10 mRNA expression increased in the inoculated mammary glands 24 hours after inoculation, and it was higher in the inoculated mammary glands of sows that developed clinical signs of mastitis compared with sows that remained clinically healthy, while the expression of another anti-inflammatory cytokine, transforming growth factor-beta 1 (TGF-beta1) mRNA was unaltered, as was mRNA expression for the IL-1 receptor type I (IL-1R1). In addition, the pattern-recognition receptor (PRR) Toll-like receptor 2 (TLR2) mRNA expression increased in the inoculated as well as the non-inoculated mammary glands of sows that developed clinical signs of mastitis and of sows that remained clinically healthy. However, TLR2 mRNA expression was higher in the inoculated mammary glands than in the non-inoculated mammary glands of sows that remained clinically healthy. The findings of the present study suggest that IL-6 and/or TNF-alpha in blood could be used as markers for identification of periparturient sows with coliform mastitis, and that development of clinical symptoms of coliform mastitis is associated with the degree of local production of regulatory cytokines in response to intramammary E. coli inoculation.