Broom Leon J, Kogut Michael H
Gut Health Consultancy,Exeter,Devon,UK.
Southern Plains Agricultural Research Center, USDA-ARS,College Station,TX 77845,USA.
Anim Health Res Rev. 2018 Jun;19(1):46-52. doi: 10.1017/S1466252318000026. Epub 2018 Apr 29.
The intestine performs the critical roles of nutrient acquisition, tolerance of innocuous and beneficial microorganisms, while retaining the ability to respond appropriately to undesirable microbes or microbial products and preventing their translocation to more sterile body compartments. Various components contribute to antimicrobial defenses in the intestine. The mucus layer(s), antimicrobial peptides and IgA provide the first line of defense, and seek to trap and facilitate the removal of invading microbes. If breached, invading microbes next encounter a single layer of epithelial cells and, below this, the lamina propria with its associated immune cells. The gut immune system has developmental stages, and studies from different species demonstrate that innate capability develops earlier than acquired. In addition, various factors may influence the developmental process; for example, the composition and activity of the gut microbiota, antimicrobials, maternally derived antibodies, host genetics, and various stressors (e.g. feed deprivation). Therefore, it is clear that particularly younger (meat-producing) animals are reliant on innate immune responses (as well as passive immunity) for a considerable period of their productive life, and thus focusing on modulating appropriate innate responses should be an intervention priority. The gut microbiota is probably the most influential factor for immune development and capability. Interventions (e.g. probiotics, prebiotics, antibodies, etc.) that appropriately modulate the composition or activity of the intestinal microbiota can play an important role in shaping the desired functionality of the innate (and acquired) response. In addition, innate immune mediators, such as toll-like receptor agonists, cytokines, etc., may provide more specific ways to suitably modulate the response. A better understanding of mucosal immunology, signaling pathways, and processes, etc., will provide even more precise methods in the future to boost innate immune capability and minimize any associated (e.g. nutrient) costs. This will provide the livestock industry with more effective options to promote robust and efficient productivity.
肠道发挥着获取营养、耐受无害和有益微生物的关键作用，同时保持对不良微生物或微生物产物做出适当反应并防止它们转移到更无菌的身体腔室的能力。肠道中的各种成分有助于抗菌防御。黏液层、抗菌肽和免疫球蛋白A构成了第一道防线，旨在捕获并促进入侵微生物的清除。如果第一道防线被突破，入侵微生物接下来会遇到单层上皮细胞，其下方是含有相关免疫细胞的固有层。肠道免疫系统有发育阶段，不同物种的研究表明先天能力比后天获得的能力发育得更早。此外，各种因素可能会影响发育过程；例如，肠道微生物群的组成和活性、抗菌药物、母体来源的抗体、宿主遗传学以及各种应激源（如饲料剥夺）。因此，很明显，特别是年幼的（产肉）动物在其相当长的生产生活期间依赖先天免疫反应（以及被动免疫），因此重点调节适当的先天反应应该是干预的优先事项。肠道微生物群可能是对免疫发育和能力最有影响的因素。适当调节肠道微生物群组成或活性的干预措施（如益生菌、益生元、抗体等）在塑造先天（和后天）反应的理想功能方面可以发挥重要作用。此外，先天免疫介质，如Toll样受体激动剂、细胞因子等，可能提供更具体的方式来适当地调节反应。更好地理解黏膜免疫学、信号通路和过程等，未来将提供更精确的方法来增强先天免疫能力并最小化任何相关（如营养）成本。这将为畜牧业提供更有效的选择，以促进强健而高效生产率。
