Exploring the evolutionary links: Innate immunity in bacteria and eukaryotes

The innate immune system, present in various species, functions as the primary barrier against pathogens, preventing infection and maintaining homeostasis. It consists of mechanical, chemical, and cellular elements across eukaryotic organisms, including physical barriers, physiological processes, pattern recognition molecules, proteins, and cytokines. Despite significant taxonomic differences, both bacteria and complex multicellular organisms exhibit strikingly analogous immune system attributes. Specifically, conserved features in their anti-phage defense mechanisms include the regulation of cellular responses to cytosolic double-stranded DNA and the presence of functional nucleases for viral nucleic acid degradation. Both bacteria and eukaryotes also employ pattern recognition receptors (PRRs) with central nucleoside triphosphatases domains for phage identification and targeting, alongside shared strategies such as gasdermins and pore-forming proteins that confer protection against phages and induce cellular apoptosis. These evolutionary parallels suggest that innate immunity has deep, ancient roots and may reflect the progression of complex life forms from simpler ancestors. Understanding these similarities could inspire new therapeutic strategies and provide deeper insight into the diverse evolutionary pathways of immunity across species. The current article examines these evolutionary connections by comparing innate immune systems in bacteria and eukaryotes, focusing on shared components and molecular insights. Future research should aim to identify and bridge knowledge gaps, further elucidating the evolutionary origins and functional diversity of innate immunity across species.