Abstract
Restrictions on antimicrobials demand alternative strategies to improve broiler health, such as supplying feed additives which stimulate innate immune cells like natural killer (NK) cells. The main objective of this study was to characterize intestinal NK cells in broiler chickens during embryonic and early life and compare these to NK cells in spleen, blood and bone marrow. Also T-cell subsets were determined. The majority of intestinal NK cells expressed IL-2Rα rather than 20E5 and 5C7, and showed low level of activation. Within intestinal NK cells the activation marker CD107 was mostly expressed on IL-2Rα+ cells while in spleen and blood 20E5+ NK cells primarily expressed CD107. High percentages of intestinal CD8αα+, CD8αβ+ and from 2 weeks onward also gamma delta T cells were found.Taken together, we observed several intestinal NK subsets in broiler chickens. Differences in NK subsets were mostly observed between organs, rather than differences over time. Targeting these intestinal NK subsets may be a strategy to improve immune-mediated resistance in broiler chickens.
Highlights
Restrictions on the use of antimicrobials in poultry production have made search for other strategies to maintain or improve poultry health, such as enhanced immune responsiveness by feed interventions impor tant (Taha-Abdelaziz et al, 2018)
The majority of intestinal natural killer (NK) cells in the ileum was located in the intraepithelial lymphocytes (IEL) and expressed the IL-2Rα
The high percentage of intestinal IL-2Rα+ NK cells is in agreement with earlier studies in layer chickens and SPF chickens that showed similar per centages at similar ages (Gobel et al, 2001; Jahromi et al, 2018)
Summary
Restrictions on the use of antimicrobials in poultry production have made search for other strategies to maintain or improve poultry health, such as enhanced immune responsiveness by feed interventions impor tant (Taha-Abdelaziz et al, 2018). NK cells share many characteristics with group I innate lymphoid cells; both cells express the transcription factor T-bet and secrete Th1 cell-associated cytokines like IFNγ and TNFα as reviewed in Artis and Spits (2015). These cytokines are involved in killing of infected cells and especially IFNγ plays a role in the induction of subsequent adaptive immune responses (Fuchs et al, 2013). Human NK cells mainly reside in the intestine in frequencies of 40% in IEL, and in lower frequencies of 10–20% in blood and secondary lymphoid tissues like spleen (Caligiuri, 2008; Ferlazzo et al, 2004; Leon et al, 2003; Lynch et al, 2006). The predominantly cytotoxic NK cell subset was shown in humans and mice to be circulating (Farag and Caligiuri, 2006; Lanier et al, 1986), whereas the mainly cytokine-producing subset is observed in tissues in close contact with T cells (Cooper et al, 2001; Farag and Caligiuri, 2006)
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