Investigation of immune response to Eimeria maxima in broilers

Body: Xylooligosaccharides (XOS) represent a prebiotic candidate demonstrated to increase bifidobacteria in mice feces when supplemented in the diet. As this bifidogenic effect has only been demonstrated in fecal samples, the aim of this study was to investigate if XOS changes the microbiota throughout the entire intestine and examine its effects on mucosal and systemic immune parameters in mice. A 10% XOS supplemented diet revealed a significant increase in the Bifidobacterium group throughout all segments of the intestine with the highest relative increase in ileum. In intestinal epithelial cells (IEC), most genes involved in innate immune responses were unaffected, while the expression of the defensin RegIII (cid:534) , known to limit bacterial colonization of the mucosal surface, was significantly up-regulated in the small intestine. The up-regulation of RegIII (cid:534) may explain the unaffected innate immune response seen in this study, as the homeostatic spatial relationship between the gut microbiota and the host is maintained regardless of the increase in the Bifidobacterium group. We hypothesized that the XOS diet increases SCFA production, and when absorbed, this leads to increased SCFA in the blood. Here, SCFAs bind to the SCFA receptor GPR43 on neutrophils, causing a down-regulation of the pro-inflammatory cytokine IL1 (cid:533) . Indeed, the Il1 (cid:533) and also Ifn (cid:534) expression were significantly decreased by XOS diet, in-dicating that SCFAs modulate the systemic immune response. In vitro treatment of whole blood with propionate led to a decrease in the Il1 (cid:533) expression, thus supporting that increased SCFA production was involved in the Il1 (cid:533) down-regulation observed in the XOS fed mice. A decreased proportion of IFN- (cid:534) producing CD4 T cells were detected in mesenteric lymph nodes of XOS fed mice, but not in spleen. Together with the Il1 (cid:533) and Ifn (cid:534) reduction in blood, this supports an anti-inflammatory effect of XOS diet in both mucosal and systemic immune compartments. Taken together, our results show that XOS feeding decreases systemic and mucosal inflammation and this effect is likely to be due to an increase in bifidobacteria in the small intestine leading to up-regulation of RegIII (cid:534) and increased SCFA production. Abstract Body: Background: Immature dendritic cells (DC) engulf large volumes of extracellular fluid through macropinocytosis. This may be increased further upon ligation of single TLR ligands such as LPS and PAM3CSK4 to TLR on DC (West et al. 2004). In contrast, phagocytosis of bacteria is dependent on specific sequential interactions between the surface of the bacteria and receptors on the DC. How these two different modes of uptake affect the immune response is not well understood. Lactobacillus acidophilus induces a strong IFN- (cid:533) response in bone-marrow derived DC (BMDC) . The induction is dependent on internalization as well as on spleen tyrosine kinase (Syk) signalling (Weiss et al. 2010). Syk is also known to play a role in different types of endocytosis (Y. Tohyama and H.Yamamura 2009). We hypothesise that L. acidophilus uptake via phagocytosis is a prerequisite for IFN- (cid:533) induction. Objective : In the present work the aim is to study the nature of endocytosis involved in uptake of L. acidophilus by DC and how this affects the induction of IFN- (cid:533) . Methods: Endocytosis in DC was quantified by measuring the uptake of fluorescence-labelled dextran or bacteria by flow cytometry and visualised by confocal microscopy. Induction of IFN- (cid:533) and other cytokines in BMDC was measured by QPCR and ELISA. Results: Increased macropinocytosis was induced upon stimulation with the TLR ligands LPS, Pam3CSK4 and the Gram negative E. coli , but not by L. acidophilus . Addition of LPS, Pam3CSK4, or E. coli to the BMDC 30 minutes prior to L. acidophilus increased the uptake of L. acidophilus