"Concomitant to the unravelling of bacterial immune defence was the realisation that some antiphage systems are in fact conserved in eukaryotes [7–9]. For example, cyclic GMP-AMP synthase (cGAS)-like enzymes, which produce cyclic dinucleotide second messengers upon pathogen detection, and viperins, which generate modified nucleotides blocking viral replication, protect bacteria and humans alike. Contrary to the conceptual framework of clade-specific immune mechanisms, a fraction of immune modules (domains or proteins involved in defence) are conserved between prokaryotes and eukaryotes."
https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3002717