Immune system of the uterus in cows and its functions – selected issues.

Phagocytosis is the most important defense mechanism of uterus anti-infective response. This process involves specialized phagocytic cells, mainly polymorphonuclear neutrophils (PMN), monocytes and macrophages belonging to inborn mechanisms, which are constantly present in the uterus, or are transferred from an inflammation site as a specific response. The role of these cells is not only pathogens absorption and their intracellular killing, but also an elimination of dead tissues parts, which is especially important in the uterus in the postpartum period. Additionally, cytokines secreted by them after the contact with pathogens enhance further defense stages. The cells belonging to inborn defense mechanisms, recognize the microorganisms due to a specialized group of non-specific immunity receptors, referred to as pattern recognition receptors (PRRs). A few groups of these receptors have been recognized and described, and the classical and the best recognized example in uterus are toll-like receptors (TLR). These receptors have an ability of recognition of constant microorganisms components, so called group structures referred to as PAMPs (pathogen associated molecular patterns), which despite pathogens mutation stay unchanged, since they are essential for their survival (e.g. cellular membrane or nucleic acids parts). After pathogens penetration to uterus, they are recognized by the TLR system of the immunological system and uterine epithelium cells. Activated cells of non-specific immunity release proinflammatory cytokines, chemokines and defensins, which task is to support infection elimination, chemotaxis of active immune cells (neutrophils, macrophages, dendritic cells, mast cells) and to activate specific immunological response. Moreover, an activation of TLR receptors on the surface of macrophages leads both to an enhanced synthesis of proinflammatory cytokines, interleukin 1, 6, 8 and TNF-α, but they also increase their phagocytic ability and cause an increase in reactive oxygen species formation and nitrogen oxide synthesis. The kind of leucocytes sub-population contributing in immunological response seems to be of a key significance in infections elimination and protection of own organism’s tissues. A significant role in this range has been recently attributed to regulatory cells. Recent studies have also shown that intrauterine administered substances can have a significant effect on local uterine immunity. Understanding the impact of these preparations may contribute to the development of more effective treatments for uterine inflammation.