Assessment of trade-offs between feed efficiency, growth-related traits, and immune activity in experimental lines of layer chickens

Table 3 Identification of immune cell populations in chicken blood and putative functions in anti-viral immunity

Immune system	Blood immune cell populations^a	Cell surface markers (labeled with monoclonal antibodies)^b	Functions^c
Innate	Myeloid cells		Immediate non-specific response
	Heterophils	CD45dim population, no specific marker	Inflammation, phagocytosis, anti-microbial activity
	Monocytes	CD45bright population KUL01+	Inflammation, phagocytosis, anti-microbial activity; antigen presentation
Adaptive	Lymphocytes	CD45bright populations	Delayed response, virus-specific memory triggered after vaccination
	T cells^d	Including all CD4⁺, CD8α⁺, TCRγδ⁺
	TCRγδ⁺	CD8α⁺ or CD8α⁻	Interface between innate and adaptive immunity
	TCRγδ⁻		Delayed response, virus-specific memory triggered after vaccination
	Helper	CD4⁺	Help for anti-viral specific antibody and cytotoxic responses
	Cytotoxic	CD8α⁺	Anti-viral specific cytotoxic responses and IFN-γ production
	B cells	BU1⁺	Specific antibody (neutralizing) production

^aFACS analysis was performed according to Seliger et al. [40]. NK cells and myeloid dendritic cells were not tested because they are not well characterized in chicken blood and are assumed to be rare (less than 1% of leucocytes)
^bReferences for monoclonal antibodies are in Seliger et al. [40]
^cFunctions of immune cell populations are indicative. More details are available in the book Avian Immunology [96]
^dExpressions of the T cell receptor (TCR) αβ and γδ are mutually exclusive. TCRαβ is involved in antigen peptide recognition after presentation via MHC I/II molecules. TCRγδ is involved in recognition of a variety of antigens (including peptides, lipids, glycol-lipids, and phospho-antigens). The FACS strategy to separate helper and cytotoxic T cells in chicken blood was based on the expression or the absence of expression of TCRγδ [40]. The CD4⁺ helper T cell subset expresses only TCRαβ (not tested). CD8α⁺ T cells express TCRγδ or TCRαβ (not tested), the latter of which includes anti-viral cytotoxic T cells. TCRγδ⁺ T cells include CD8α⁺ and CD8α⁻ T cell subsets that may display cytotoxic activity against tumor cells and/or IFN-γ production

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