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

Figures & data

Table 1. Ontogeny of innate immune system cells in chickens.

Tissues	Times lines
	Before hatch (Embryonation day, ED)					Post-hatch (Weeks)
	ED1-4	ED5-8	ED9-12	ED13-16	ED17-21	Week 1	Weeks 2–3	Weeks 4–6
Yolk sac	CD45+ cells
Blood	CD2+ cells					Heterophils, Monocytes	Heterophils
Bursa of Fabricius		CD45+ cells, DCs						Various types of DCs
Thymus					Thymic DCs
Spleen			CD45+ cells, Macrophages	NK cells, γδ T cells		γδ T cells		γδ T cells, various types of DCs
Caecal tonsil			CD45+ cells, γδ T cells
Intestine				γδ T cells	NK cells	Heterophils
Skin		CD45+ cells, Langerhans cells

Notes: First appearance of various cell types in tissues of pre- or post-hatch chickens is indicated in each column. In cases where there are reports of an increase in cell numbers during development in each tissue, cell types are repeated for that tissue. For example, γδ T cells appear in the spleen by ED13-16 and their numbers increase by week 1 and weeks 4-6 post-hatch. The data in this table are obtained from studies that used healthy broiler or specific-pathogen-free chickens.

Table 2. Ontogeny of innate response genes and receptors in chickens.

Tissue	Times lines
	Before hatch (Embryonation days, ED)					Post-hatch (Weeks)
	ED1-4	ED5-8	ED9-12	ED13-16	ED17-21	Week 1	Weeks 2–3	Weeks 4–6
Bursa of Fabricius						CATH1-3
Spleen			IL-4,10,18, IFNγ	IFNα, β IFNλ	IFNγ	CATH2-3, MDA5 TLR3, 7	IFNαR1, αR2, IL-10R2, IFNλR1, IFNλ	IFNα, β, IFNλ
Intestine/Caecum			CATH1-3, Most AvBD		CATH2, AvBD9 TLR21	IFNγ	AvBD1,2,4,6
Lung			Some AvBD		IFNα, β	MDA5, TLR3,7	IFNαR1, αR2, IL-10R2, IFNλR1	TLR7, IFNλ
Whole embryo	All TLRs

Notes: First evidence for expression of innate response or receptor genes in tissues of pre- or post-hatch chickens is indicated in each column. In cases where there are reports of an increase in expression during development in each tissue, gene names are repeated for that tissue. For example, expression of IFNα, β can be recorded as early as ED13-16 but their expression increases over time and there is evidence for enhanced expression of these molecules by weeks 4-6. The data in this table are obtained from studies that used healthy broiler or specific-pathogen-free chickens, with no clinical infections or treatment with TLR ligands.