Abstract
Simple SummaryThe article reviews the defence mechanisms and the relevant processes that occur in the udder of sheep. Due to the importance of the udder in milk production, animals display many defences to protect the organ. These include the teats, the epithelial and the white-blood cells in the udder, the immunoglobulins and chemical substances that all participate in the various processes. These are influenced by many factors, animal- or management-regulated, which must be taken into account in the formulation of prevention schemes against mastitis in sheep.The objectives of this review paper are to present udder defences, including teat of the udder, mammary epithelial cells, leucocytes, immunoglobulins, complement system and chemical antibacterial agents, to describe cooperation and interactions between them and to elaborate on potentials regarding their significance in mammary immunisation strategies. The teat of the udder provides initial protection to the mammary gland. The mammary epithelial cells synthesise antibacterial proteins and the leucocytes produce various inflammation mediators (cytokines or chemokines), phagocytose bacteria and recognise antigenic structures. In the mammary gland, four immunoglobulins (IgG1, IgG2, IgM and IgA) have important roles against bacterial pathogens. The complement system is a collection of proteins, participating in the inflammatory process through various pathways. Other components contributing to humoral mammary defence include lactoferrin, lysozyme and the lactoperoxidase/myeloperoxidase systems, as well as oligosaccharides, gangliosides, reactive oxygen species, acute phase proteins (e.g., haptoglobin and serum amyloid A), ribonucleases and a wide range of antimicrobial peptides. Management practices, genetic variations and nutrition can influence mammary defences and should be taken into account in the formulation of prevention strategies against ovine mastitis.
Highlights
Many specific or non-specific mechanisms of varying significance and involvement, which include humoral and cellular immune processes, are responsible for the defence of the mammary gland
In the case of S. aureus, which is an important mammary pathogen in ewes [52], activation of the mammary gland in its entirety was found to be necessary for clearance of the infection [49]
Recent work performed in ewes, has indicated that presence of lactoferrin genotype AA was associated with lower prevalence of subclinical mastitis [106]
Summary
Many specific or non-specific mechanisms of varying significance and involvement, which include humoral and cellular immune processes, are responsible for the defence of the mammary gland. Non-specific or specific defence mechanisms active in the mammary gland are part of the innate or adaptive immune systems, respectively. The objectives review paper werewere to present mammary defences The objectives ofofthis this review paper to present mammary defences (teat of the udder, epithelial cells, leucocytes, immunoglobulins and complement system, chemical antibacterial agents) mammary epithelial cells, leucocytes, immunoglobulins and complement system, chemical and to describe cooperation and interactions between them. Teat closure after milking, effected by the local teat musculature, is paramount (“keratin flush”) [1,4]. Teat closure after milking, effected by the local teat musculature, is paramount forinhibiting inhibitingbacterial bacterialentrance. During the during dry-period, accumulation of keratin atof the teat orifice teat mammary. The dry-period, accumulation keratin at theseals teat the orifice preventing entrance. The inducible present at the border between teat duct cistern, Further, the induciblelymphoid lymphoidnodules, nodules, present at the border between teat and ductteat and teat play a pivotal role in udder defence [3,10]
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