Gut immunity: Its development and reasons and opportunities for modulation in monogastric production animals

Authors: BROOM, LEON - University Of Leeds; Kogut, Michael - Mike

Submitted to: Animal Health Research Reviews
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2018
Publication Date: 4/29/2018
Citation: Broom, L., Kogut, M.H. 2018. Gut immunity: Its development and reasons and opportunities for modulation in monogastric production animals. Animal Health Research Reviews. 19(1):46-52. https://doi.org/10.1017/S1466252318000026.
DOI: https://doi.org/10.1017/S1466252318000026

Interpretive Summary: The development of the immune response in young chicks occurs in the animal's gut. This is because the gut is exposed to not only nutrients, but also many bacteria that live in the gut. What has been found over the last 20 years, is that bacteria that do not cause disease, but normally grow in the gut can work together to make the animal's immune system work better and prevent the harmful germs from growing. This paper shows that the growth of specific bacteria control specific components of the chick's local immune environment in the gut. Understanding the immune response in chicks is important not only to veterinary medicine, but also to human medicine. Poultry play an important role in the spread of emerging infectious diseases, such as salmonellosis and avian influenza, that can have a huge impact on human health. Understanding how the chick responds to these germs can help the medical field better understand how to care for and treat humans that may also get infected. This paper will be beneficial to chicken growers, microbiologists, and nutritionists and will help make better animal feeds that encourage the growth of the normal bacteria in the gut and help the development of a healthy immune system, thus, making it possible to help the immune response without causing damage to the chick.

Technical Abstract: The intestine must perform the critical role of nutrient acquisition whilst preventing the passage of undesirable microbes or microbial products from the external environment to sterile body compartments. Various components contribute to antimicrobial defenses in the intestine. The mucus layer(s), antimicrobial peptides (AMPs), and IgA provide the first line of defense and seek to trap and facilitate the removal of invading microbes. If breached, invading microbes will next encounter a single layer of epithelial cells and below this, the lamina propria with its associated immune cells. Both epithelial and immune cells express pattern recognition receptors (PRRs) that detect microbe- or damage-associated molecular patterns (MAMPs and DAMPs), which then initiate various extracellular activation cascades and intracellular signaling pathways, leading to an inflammatory response, recruitment of phagocytic cells for clearance of the pathogens, and mobilization of professional antigen-presenting cells. The gut immune system has developmental stages and studies from different species, which demonstrates 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’s 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 and/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 (TLR) agonists, cytokines, etc., may provide more specific ways to suitably modulate the response. 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.