Ratzka Carolin, Gross Roy, Feldhaar Heike
Department of Microbiology, Biocentre, University of Würzburg, 97074, Germany.
Animal Ecology I, University of Bayreuth, 95440, Germany.
Insects. 2012 Jun 15;3(2):553-72. doi: 10.3390/insects3020553.
Bacterial endosymbioses are very common in insects and can range from obligate to facultative as well as from mutualistic to pathogenic associations. Several recent studies provide new insight into how endosymbionts manage to establish chronic infections of their hosts without being eliminated by the host immune system. Endosymbiont tolerance may be achieved either by specific bacterial adaptations or by host measurements shielding bacteria from innate defense mechanisms. Nevertheless, insect hosts also need to sustain control mechanisms to prevent endosymbionts from unregulated proliferation. Emerging evidence indicates that in some cases the mutual adaptations of the two organisms may have led to the integration of the endosymbionts as a part of the host immune system. In fact, endosymbionts may provide protective traits against pathogens and predators and may even be required for the proper development of the host immune system during host ontogeny. This review gives an overview of current knowledge of molecular mechanisms ensuring maintenance of chronic infections with mutualistic endosymbionts and the impact of endosymbionts on host immune competence.
细菌内共生现象在昆虫中非常普遍，其范围从专性共生到兼性共生，以及从互利共生到致病关联。最近的几项研究为内共生体如何在不被宿主免疫系统清除的情况下成功建立对宿主的慢性感染提供了新的见解。内共生体的耐受性可以通过特定的细菌适应性或通过宿主的调节机制来实现，这些机制可以保护细菌免受先天性防御机制的影响。然而，昆虫宿主也需要维持控制机制，以防止内共生体不受控制地增殖。新出现的证据表明，在某些情况下，两种生物的相互适应可能导致内共生体整合为宿主免疫系统的一部分。事实上，内共生体可能提供针对病原体和捕食者的保护特性，甚至在宿主个体发育过程中，宿主免疫系统的正常发育可能需要内共生体。本综述概述了目前关于确保与互利内共生体维持慢性感染的分子机制以及内共生体对宿主免疫能力影响的知识。
