Fig. 1

Major differences in immunity of C. elegans, D. melanogaster and mammals. Invertebrates, such as nematodes and insects, represented by C. elegans and D. melanogaster respectively, completely rely on innate immunity upon infection, while vertebrates (represented by mammals) have also evolved an adaptive immune system. Cellular immunity occurs in fruit flies as hemocytes (immune cells in the hemolymph), and as different types of leukocytes in mammals, but is absent in worms. In contrast to this, the germ-line encoded complement system is unique to mammals. Moreover, pattern recognition receptors (PRRs) of the innate immune system – most prominently the Toll- and Toll-like receptors, are incremental for pathogen-recognition in fruit flies and mammals, but whether the single Toll-like receptor homolog in C. elegans fulfils the same function is still under debate. Finally, Nf-κB transcription factors, which regulate the expression of immune-related genes, are central to D. melanogaster and mammalian immunity, but have not been identified in C. elegans. The well-known cross-talk between immune and JNK MAPK signalling is indicated, but notably several other pathway interactions do also exist. Immunity genes and protein complexes also associated with lifespan and ageing are marked in green and bold