Novel model for chronic intestinal inflammation in chickens: (2) Immunologic mechanism behind the inflammatory response

Intestinal inflammation in poultry is a complex response that involves immune and intestinal cells which is still not fully understood. Thus, to better understand the mechanisms that drive the chronic intestinal inflammation in fowl we conducted an experiment applying a previously established nutritional model of low-grade chronic intestinal inflammation to evaluate cytokine and chemokine profiles in the chicken intestine. For this, we placed 90 one-day chickens into two treatments: (1) a control group (CNT) fed a corn-soybean diet, and (2) a group fed a diet high in non-starch polysaccharides (NSP). At days 14, 22, 28 and 36 of age, 6 birds from each treatment were euthanized, jejunal and ileal samples were collected for histological examination and cytokine measurements. The cytokines interferon-alpha (IFN-α), IFN-γ, interleukin-16 (IL-16), IL-10, IL-21, IL-6, macrophage-colony stimulating factor (M-CSF), chemokine C–C motif ligand 20 (CCL20), CCL4, CCL5 and vascular endothelial growth factor (VEGF) were quantified in the intestinal tissue. Histologically, both jejunum and ileum of broilers fed NSP diet showed marked infiltration of mononuclear immune cells into the villi. Further, these birds exhibited a significant (P < 0.05) increase in CCL20 concentration in the jejunum at 14d, but a dramatic reduction of M-CSF at 14 and 21d. Later at 28d and 36d, birds fed the NSP diet exhibited increased IL-16 concentration in the jejunum. Since M-CSF is a monocyte stimulatory cytokine and CCL20 a chemokine of T-cells, the reduced M-CSF and increased production of CCL20 may indicate the involvement of the adaptive immune response, specifically driven by T-cells, occurring around the third week of age in the NSP model. Lastly, as a result of the mononuclear cell infiltration and activation of T-cells, IL-16, a pro-inflammatory T-cell cytokine, increased. Therefore, the current work indicates the importance of adaptive immune cells, especially T-cells, in the chronic intestinal inflammation in broiler chicken.