Published in Scientific Works. Series C. Veterinary Medicine, Vol. LX (1)
Written by Tiberiu CONSTANTIN, Ion Alin BÎRȚOIU
The reproductive tractus presents a series of innate defending (nonspecific) mechanisms and adaptative (specific) mechanisms, that can be affected by the endocrine status during pregnancy and puerperium. The conceptus grows under correct function of the immune system of the cow. One cytokine in particular, colony-stimulating factor 2, can promote preimplantation development and cause changes in conceptus function that increase the possibilities the conceptus develops to term. The puerperal period is characterized by an increased risk of uterine infections due to anatomic barriers which remain open for a few days. In this case bacteria are detected by the endometrial specialized immune cells which have toll-like receptors for the bacterial liants like peptidoglycans and lipopolysaccharides. The activation toll-like receptors enhances the synthesis and production of pro-inflammatory cytokins like the α tumoral necrosis factor and nitric oxide, which mobilizes the immunitary cells. There are at least 11 types of toll-like receptors which recognize bacterial and viral particles. Toll-like receptor 2 detects the peptidoglycan associated with lipoteichoic acid, lypopeptides and zimoshan, while toll-like receptor 4 and 9 recognize single liants, lipopolysaccharides and unmetilated bacterial DNA. Polimorphonuclear leukocytes (mainly neutrophils), monocytes and circulant macrophages, represent the first line defence against bacteria. Neutrophilic phagocytant activity is initiated by complement system and antibodies. Interleukin 6 appears in the first inflammatory stage, activates mature neutrophils, helps in their maturation, differentiates monocytes in mature macrophages and, also, differentiates natural killer cells. The role of different immunoglobulines (IgA, IgG, IgM) in local defence mechanisms and the endometrial synthesis rate or in other layers of the bovine reproductive tract has not been sufficiently studied yet. Still, some of these immunoglobulins have been identified in the cervico-vaginal secretions of cows infected with Campylobacter fetus. Preparturtm period is accompanied by peripheral leucocytosis which is followed by peripheric leucopenia during the first week post-partum.
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