Evolution of host innate defence: insights from Caenorhabditis elegans and primitive invertebrates

The soil nematodeCaenorhabditis elegans is easy to manipulate genetically and is therefore a useful model organism. But C. elegansdoes not use its Toll-like receptor homologue for immune defence. So what can it tell us about the origins and functions of other immune defence pathways in higher organisms? The genetically tractable model organism Caenorhabditis elegans was first used to model bacterial virulence in vivo a decade ago. Since then, great strides have been made in identifying the host response pathways that are involved in its defence against infection. Strikingly, C. elegans seems to detect, and respond to, infection without the involvement of its homologue of Toll-like receptors, in contrast to the well-established role for these proteins in innate immunity in mammals. What, therefore, do we know about host defence mechanisms in C. elegans and what can they tell us about innate immunity in higher organisms?