Intestinal eosinophils, homeostasis and response to bacterial intrusion

Abstract

Eosinophils are traditionally considered as end-stage effector cells involved in the pathogenesis of Th2 immune-mediated disorders as well as in the protection against parasite infection. However, this restricted view has recently been challenged by a series of studies revealing the highly plastic nature of these cells and implication in various homeostatic processes. Large numbers of eosinophils reside in the lamina propria of the gastrointestinal tract, at the front line of host defence, where they contribute to maintain the intestinal epithelial barrier function in the face of inflammation-associated epithelial cell damage. Eosinophils confer active protection against bacterial pathogens capable of penetrating the mucosal barrier through the release of cytotoxic compounds and the generation of extracellular DNA traps. Eosinophils also integrate tissue-specific cytokine signals such as IFN-γ, which synergise with bacterial recognition pathways to enforce different context-dependent functional responses, thereby ensuring a rapid adaptation to the ever-changing intestinal environment. The ability of eosinophils to regulate local immune responses and respond to microbial stimuli further supports the pivotal role of these cells in the maintenance of tissue homeostasis at the intestinal interface.

Role of Eosinophils in Intestinal Inflammation and Fibrosis in Inflammatory Bowel Disease: An Overlooked Villain?

“…Lastly, eosinophils have been described to secrete the IL-1 receptor antagonist IL-1Rα thereby inhibiting IL-1β production resulting in decreased Th17 differentiation. As Th17 cells are the main producers of the profibrotic cytokine IL-17A, eosinophils can fulfill an anti-fibrotic role as well ( 172 ).…”

Systematic Characterization of the Disruption of Intestine during Liver Tumor Progression in the xmrk Oncogene Transgenic Zebrafish Model

“…This method has also been previously used to observe these cell types in the zebrafish intestine [ 36 , 37 , 38 ]. Both goblet cells and eosinophils are essential for the maintenance of intestinal epithelial barrier function and intestine homeostasis [ 39 , 40 ], and deregulation in the number or function is associated with diseases such as inflammatory bowel disease (IBD), intestinal cancers and bacterial and parasitic infections of the intestine [ 39 , 41 ]. Compared to wt, xmrk fish showed increased eosinophil and goblet cell counts in all intestinal segments ( Figure 2 B,C).…”

Eosinophils in the Gastrointestinal Tract: Key Contributors to Neuro-Immune Crosstalk and Potential Implications in Disorders of Brain-Gut Interaction

“…During the last decade, Eosinophils are innate immune granulocytes involved in the defense against parasites and in the pathogenesis of Th2 immune-mediated disorders [1]. During the last decade, the prevailing paradigm indicating that eosinophils act as strictly pro-inflammatory end-stage effector cells is being progressively replaced by cumulative observations showing that eosinophils are multifaceted fine-tuned tissue residents that are involved in multiple phases of the immune response, participate in tissue regeneration, and play a role in homeostasis maintenance [2][3][4]. The wide variety of receptors expressed by eosinophils and their ability to produce and release a myriad of mediators enable them to develop tight and complex bi-directional communication with almost every tissular component, including epithelial immune cells and neurons (Figure 1), as recently described in the context of asthma and allergic respiratory inflammation [3,5].…”