LSU Health, Department of Microbiology and Immunology, Louisiana State University (LSU), Shreveport, LA 71103, USA.
Int J Mol Sci. 2021 Jul 27;22(15):8004. doi: 10.3390/ijms22158004.
Eosinophils are granulocytes primarily associated with T2 responses to parasites or immune hyper-reactive states, such as asthma, allergies, or eosinophilic esophagitis. However, it does not make sense from an evolutionary standpoint to maintain a cell type that is only specific for parasitic infections and that otherwise is somehow harmful to the host. In recent years, there has been a shift in the perception of these cells. Eosinophils have recently been recognized as regulators of immune homeostasis and suppressors of over-reactive pro-inflammatory responses by secreting specific molecules that dampen the immune response. Their role during parasitic infections has been well investigated, and their versatility during immune responses to helminths includes antigen presentation as well as modulation of T cell responses. Although it is known that eosinophils can present antigens during viral infections, there are still many mechanistic aspects of the involvement of eosinophils during viral infections that remain to be elucidated. However, are eosinophils able to respond to bacterial infections? Recent literature indicates that triggers T2 responses mediated by eosinophils; this promotes anti-inflammatory responses that might be involved in the long-term persistent infection caused by this pathogen. Apparently and on the contrary, in the respiratory tract, eosinophils promote T17 pro-inflammatory responses during infection, and they are, in fact, critical for early clearance of bacteria from the respiratory tract. However, eosinophils are also intertwined with microbiota, and up to now, it is not clear if microbiota regulates eosinophils or vice versa, or how this connection influences immune responses. In this review, we highlight the current knowledge of eosinophils as regulators of pro and anti-inflammatory responses in the context of both infection and naïve conditions. We propose questions and future directions that might open novel research avenues in the future.
嗜酸性粒细胞是主要与寄生虫 T2 反应或免疫超敏反应状态相关的粒细胞，如哮喘、过敏或嗜酸性食管炎。然而，从进化的角度来看，维持一种仅针对寄生虫感染的细胞类型是没有意义的，而这种细胞类型在其他方面对宿主是有害的。近年来，人们对这些细胞的认识发生了转变。嗜酸性粒细胞最近被认为是免疫稳态的调节剂，通过分泌特定的分子来抑制过度活跃的促炎反应，从而抑制免疫反应。它们在寄生虫感染中的作用已经得到了很好的研究，它们在对蠕虫的免疫反应中的多功能性包括抗原呈递以及调节 T 细胞反应。虽然已知嗜酸性粒细胞在病毒感染期间可以呈递抗原，但嗜酸性粒细胞在病毒感染期间的参与仍有许多机制方面需要阐明。然而，嗜酸性粒细胞能否对细菌感染作出反应？最近的文献表明， 触发嗜酸性粒细胞介导的 T2 反应；这促进了抗炎反应，可能参与了这种病原体引起的长期持续感染。显然，相反地，在呼吸道中，嗜酸性粒细胞在 感染期间促进 T17 促炎反应，实际上，它们对于从呼吸道早期清除细菌至关重要。然而，嗜酸性粒细胞也与微生物群交织在一起，到目前为止，尚不清楚微生物群是否调节嗜酸性粒细胞，反之亦然，或者这种联系如何影响免疫反应。在这篇综述中，我们强调了嗜酸性粒细胞作为感染和原始状态下促炎和抗炎反应调节剂的最新知识。我们提出了一些问题和未来的方向，这些问题和方向可能为未来开辟新的研究途径。
