Sanitary conditions modulate proinflammatory cytokine response of broilers

Sanitary conditions influence the animal's adaptive immune response and body weight. Low sanitary conditions (LSC), defined as the conditions with high (bacterial) antigenic pressure, were shown to reduce body weight gain of pigs and chickens and increase their natural antibody levels in plasma or serum. The aim of this study was to investigate how sanitary conditions can modulate the inflammatory immune response of broilers. To test this, broiler type chickens kept under LSC or high sanitary conditions (HSC) received a respiratory challenge with lipopolysaccharides (LPS), and their in vivo and ex vivo immune responses were compared. We measured cytokine levels in plasma before and after LPS challenge, and in culture supernatants of isolated monocytes after the LPS challenge. We found that broilers kept under LSC, in comparison to HSC, had higher systemic interferon (IFN)-γ levels in plasma from 0 h to 24 h, and lower IL-10 levels at 48 h after LPS challenge. Monocytes from broilers kept under LSC produced more IL-10 and less IL-12p40 than monocytes from broilers kept under HSC, which resulted in higher IL-10:IL-12 ratios in those chickens. In conclusion, LSC modulated the immune response by inducing a stronger anti-inflammatory (IL-10) response towards the LPS challenge. The exact mechanism behind this modulation still needs to be established, as well as possible consequences of this stronger anti-inflammatory responses for the chicken's susceptibility to future infections.