Regulation of innate immunity within the bovine endometrium during infection.

Abstract

Abstract The innate immune response of the endometrium is crucial to achieve early and quick defence against pathogenic organisms that invade the reproductive tract and the uterus, before the adaptive immune response which develops much later. This early innate response is important to avoid the development of uterine disease that impacts negatively on fertility. This review is focused on the regulation of innate immunity within the bovine endometrium during infection. Although a phagocytic barrier to infection is provided by leucocytes, many recent studies have increasingly recognized the important roles of endometrial epithelial and stromal cells in early microbial detection, cellular and inter-cellular signalling, and secretion of immune/inflammatory mediators that can promote leucocyte recruitment and migration to the uterus and endometrium. Components of the endometrial innate immune response involve an increase in the expression of inflammatory products and innate immune mediators including antimicrobial peptides, mucins, pro-inflammatory cytokines including chemokines, acute phase proteins, type I interferons and prostaglandins. However, endometrial innate immunity can be influenced by many factors including infection with a number of pathogenic bacteria, viruses such as bovine viral diarrhoea virus and bovine herpes virus-4; fluctuating levels of the ovarian steroid hormones oestradiol and progesterone; and periparturient changes in body metabolism involving energy substrates and metabolites, metabolic hormones and protein metabolites. This review highlights the recent understandings on how these factors may regulate the endometrial innate immunity, although some of the underlying mechanisms are not yet clearly defined.