The battle between microbes and their viruses is ancient and ongoing. Clustered regularly interspaced short palindromic repeat (CRISPR) immunity, the first and, to date, only form of adaptive immunity found in prokaryotes, represents a flexible mechanism to recall past infections while also adapting to a changing pathogenic environment. Critical to the role of CRISPR as an adaptive immune mechanism is its capacity for self versus non-self recognition when acquiring novel immune memories. Yet, CRISPR systems vary widely in both how and to what degree they can distinguish foreign from self-derived genetic material. We document known and hypothesized mechanisms that bias the acquisition of immune memory towards non-self targets. We demonstrate that diversity is the rule, with many widespread but no universal mechanisms for self versus non-self recognition.

微生物与其病毒之间的斗争是古老而持续的。聚集规则间隔短回文重复 (CRISPR) 免疫是在原核生物中发现的第一种也是迄今为止唯一一种适应性免疫，它代表了一种灵活的机制，可以回忆过去的感染，同时适应不断变化的致病环境。CRISPR 作为一种适应性免疫机制的关键作用在于其在获得新的免疫记忆时进行自我与非自我识别的能力。然而，CRISPR 系统在区分外来遗传物质和自身遗传物质的方式和程度方面存在很大差异。我们记录了已知和假设的机制，这些机制使免疫记忆的获得偏向非自我目标。我们证明多样性是规则，