This delightful Perspective provides an exciting overview of how human innate immunity is based on bacterial systems, pointing to common ancestry, and not to convergent evolution.

Wein, T., Sorek, R. Bacterial origins of human cell-autonomous innate immune mechanisms. Nat Rev Immunol 22, 629–638 (2022).

A series of prominent research papers in the past 4 years has revolutionized insights into shared immunity between prokaryotes and eukaryotes. These build on the identification of the CRISPR-Cas system 15 years ago (Nobel prize 2020), now identifying more than 50 bacterial defence systems, organized in genetic ‘defence islands’ in bacteria.

Figure 2 providing a potential evolutionary scenario how immune mechanisms are conserved between prokaryotes and eukaryotes will undoubtedly find its way into many educational lectures.

Dual authors Tanita Wein and Rotem Sorek importantly state “… it is remarkable that the conservation with bacterial counterparts has only been described recently. This is partially attributed to the rapid evolution of immune genes, which are subject to rapid and frequent ‘selective’ sweeps owing to the arms race between pathogens and their hosts. Likely as a result of many such sweeps over the course of evolution, one cannot detect significant sequence similarity when directly comparing human immune genes such as those encoding cGAS, STING or gasdermin with their bacterial counterparts”.