Development of innate immunity in chicken embryos and newly hatched chicks: a disease control perspective

Abstract

Newly hatched chickens are confronted by a wide array of pathogenic microbes because their adaptive immune defences have limited capabilities to control these pathogens. In such circumstances, and within this age group, innate responses provide a degree of protection. Moreover, as the adaptive immune system is relatively naïve to foreign antigens, synergy with innate defences is critical. This review presents knowledge on the ontogeny of innate immunity in chickens pre-hatch and early post-hatch and provides insights into possible interventions to modulate innate responses early in the life of the bird. As in other vertebrate species, the chicken innate immune system which include cellular mediators, cytokine and chemokine repertoires and molecules involved in antigen detection, develop early in life. Comparison of innate immune systems in newly hatched chickens and mature birds has revealed differences in magnitude and quality, but responses in younger chickens can be boosted using innate immune system modulators. Functional expression of pattern recognition receptors and several defence molecules by innate immune system cells of embryos and newly hatched chicks suggests that innate responses can be modulated at this stage of development to combat pathogens. Improved understanding of innate immune system ontogeny and functionality in chickens is critical for the implementation of sound and safe interventions to provide long-term protection against pathogens. Next-generation tools for studying genetic and epigenetic regulation of genes, functional metagenomics and gene knockouts can be used in the future to explore and dissect the contributions of signalling pathways of innate immunity and to devise more efficacious disease control strategies.

Molecular Characterization and Determination of Relative Cytokine Expression in Naturally Infected Day-Old Chicks with Chicken Astrovirus Associated to White Chick Syndrome

“…To our knowledge, this the first report of early life cytokine gene expression in organs of CAstV chicks affected by WCS, demonstrating the early activation of the innate immune system of embryos and newly hatched chicks against a viral pathogen, as was previously described [45]. The present study showed that CAstV replicates in the epithelium of the intestine, lymphoid organs, and liver, but the mechanism of the generation of an innate immune response against CAstV infection in these tissues has not been fully characterized, and more studies are needed to elucidate and provide more information regarding this important topic.…”

“…These are non-acute, late immune responses. However, the affected studied animals had merely a few hours of life, so it can be speculated that this could be due to the fact that the immune responses are still immature or did not have enough time to develop [45].…”

The Potential of Toll-Like Receptors to Modulate Avian Immune System: Exploring the Effects of Genetic Variants and Phytonutrients

“…The dynamic expression of TLRs may indicate the chances of genetic modulation and production of enhanced immunological response due to higher expression levels of TLRs in chicken. The TLR2 and TLR4 are only expressed on the surface of DCs, natural killer (NK) cells, and monocytes, but intracellular expression has also been noticed in the endothelial cells (Tamiru et al, 2019). Similarly, NK cells use a variety of cellular receptors, such as Ly49 and CD94 to induce immunological responses (Boudreau and Hsu, 2018).…”

Impact of Housing Environment on the Immune System in Chickens: A Review

“…Glucocorticoid exposure to the developing brain induces alterations in gene expression, and causes a hyperresponsive HPA axis and increased anxiety behavior. Moreover, the immune function of the late embryonic and neonatal chickens is also not yet entirely developed and undergoes age-dependent variations in respect of structure and occurrence of lymphoid organs as well as immune cell distribution [200][201][202][203]. It is well known that early life experiences have long-term effects on physiology and behavior later in life in poultry [204,205].…”