Cyclic dinucleotides (CDNs) have emerged as ubiquitous signaling molecules in all domains of life. In eukaryotes, CDN signaling systems are evolutionarily ancient and have developed to sense and respond to pathogen infection. On the other hand, dysregulation of these pathways has been implicated in the pathogenesis of autoimmune diseases. Thus, CDNs have garnered major interest over recent years for their ability to elicit potent immune responses in the eukaryotic host. Similarly, ancestral CDN-based signaling systems also appear to confer immunological protection against infection in prokaryotes. Therefore, a better understanding of the host processes regulated by CDNs will be of tremendous value in many areas of research. Here, we aim to review the latest discoveries and recent trends in CDN research with a particular focus on the molecular mechanisms by which these small molecules mediate innate immunity.

中文翻译：

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环状二核苷酸位于先天免疫的最前沿。

环状二核苷酸（CDN）已经在生活的所有领域中作为普遍存在的信号分子出现。在真核生物中，CDN信号系统在进化上是古老的，并且已经发展为能够感知和响应病原体感染。另一方面，这些途径的失调与自身免疫疾病的发病机理有关。因此，近年来，CDN因其在真核宿主中引起有效免疫应答的能力而引起了人们的极大兴趣。同样，基于CDN的祖先信号系统似乎也可以提供免疫保护，防止原核生物感染。因此，更好地理解CDN调控的宿主过程将在许多研究领域中具有巨大的价值。这里，