Host–Microbe Interactions and Gut Health in Poultry—Focus on Innate Responses

Abstract

Commercial poultry are continually exposed to, frequently pathogenic, microorganisms, usually via mucosal surfaces such as the intestinal mucosa. Thus, understanding host–microbe interactions is vital. Many of these microorganisms may have no or limited contact with the host, while most of those interacting more meaningfully with the host will be dealt with by the innate immune response. Fundamentally, poultry have evolved to have immune responses that are generally appropriate and adequate for their acquired microbiomes, although this is challenged by commercial production practices. Innate immune cells and their functions, encompassing inflammatory responses, create the context for neutralising the stimulus and initiating resolution. Dysregulated inflammatory responses can be detrimental but, being a highly conserved biological process, inflammation is critical for host defence. Heterogeneity and functional plasticity of innate immune cells is underappreciated and offers the potential for (gut) health interventions, perhaps including exogenous opportunities to influence immune cell metabolism and thus function. New approaches could focus on identifying and enhancing decisive but less harmful immune processes, improving the efficiency of innate immune cells (e.g., targeted, efficient microbial killing) and promoting phenotypes that drive resolution of inflammation. Breeding strategies and suitable exogenous interventions offer potential solutions to enhance poultry gut health, performance and welfare.

Immune Modulation and the Development of Fowl Typhoid: A Model of Human Disease?

“…Enteritidis [ 2 ]. In highly susceptible gnotobiotic piglets, early neutrophil recruitment prevents Salmonella transmission from the intestine and mortality [ 24 ] and the importance of heterophil recruitment in Salmonella resistance [ 25 ] and the role of CXCLi1 and 2 [ 26 ] has also been reported in chickens. Our study therefore shows reduced iNOS/NO 2 - and CXCLi1/CXCLi2 following S .…”

Dietary Factors as Triggers of Low-Grade Chronic Intestinal Inflammation in Poultry

“…Numerous factors influence gut immune health, including the microbiota, pathogens, host genetics, host age, hygiene, medications, and management practices as described previously [2,14,21,22]. However, one overlooked factor in the overall health of the intestinal immune system is the feed and feed ingredients [2,14].…”

“…The function and mechanisms of an inflammatory response in poultry have recently been described in detail by us in a series of reviews [2,14,21,22]. Briefly, innate immune cells (macrophages, granulocytes, dendritic cells, intestinal epithelial cells) express pattern recognition receptors (PRRs) that recognize and respond to infectious microbial constituents, as microbe-associated molecular patterns (MAMPs) [23][24][25] and to endogenous host molecules released during cell death or stress, called damage associated molecular patterns (DAMPs) [14,[21][22][23][24][25]. During homeostasis, the intestinal immune tissue remains tolerant to microbiota and dietary antigens.…”

“…During homeostasis, the intestinal immune tissue remains tolerant to microbiota and dietary antigens. However, during toxic insult or infection or dysbiosis, the PRRs can activate and initiate a cascade of events that induce an inflammatory response [2,14,21,22].…”

The Control of Intestinal Inflammation: A Major Objective in the Research of Probiotic Strains as Alternatives to Antibiotic Growth Promoters in Poultry

“…Most immune cells in the intestine are distributed throughout the lamina propria and in the lymphoid aggregates. Different immune cell populations, such us heterophils, natural killer (NK) cells, macrophages, dendritic cells (DC), and T and B cells, take up the lamina propria whilst intraepithelial lymphocytes (IEL) (mostly γδ-T cells) are located among the intestinal epithelial cells (IEC) (reviewed in [89]) (Figure 1).…”