Innate immunity in C. elegans

Abstract

In its natural habitat, C. elegans encounters a wide variety of microbes, including food, commensals and pathogens. To be able to survive long enough to reproduce, C. elegans has developed a complex array of responses to pathogens. These activities are coordinated on scales that range from individual organelles to the entire organism. Often, the response is triggered within cells, by detection of infection-induced damage, mainly in the intestine or epidermis. C. elegans has, however, a capacity for cell non-autonomous regulation of these responses. This frequently involves the nervous system, integrating pathogen recognition, altering host biology and governing avoidance behavior. Although there are significant differences with the immune system of mammals, some mechanisms used to limit pathogenesis show remarkable phylogenetic conservation. The past 20 years have witnessed an explosion of host-pathogen interaction studies using C. elegans as a model. This review will discuss the broad themes that have emerged and highlight areas that remain to be fully explored.

Keywords: Antimicrobial peptide; Behavior; Damage responses; Host defence; Intercellular signaling; Model organism; Natural pathogen; Oxidative stress; Proteostasis; Stress responses.

Figure 1.

Cell-autonomous responses to infection. Examples of two canonical immune responses to infection, in the epidermis following infection by the fungus D. coniospora (Pujol et al., 2008a), and in the intestine by the bacterium P. aeruginosa (Troemel et al., 2006). Defence gene induction is observed with the transcriptional reporters, nlp-29p::GFP (left, epidermis) and irg-5p::GFP (right, intestine), the worms are visualised with an constitutive epidermal red fluorescent reporter (left) and in bright field (right).

Figure 2.

Cell-autonomous regulation of innate immunity in C. elegans. Depending on the site of infection and on the pathogen, innate immunity is regulated through diverse pathways and effectors, see text for details.

Figure 3.

Cross-tissue regulation of innate immunity in C. elegans. Innate immunity is regulated cell non-autonomously through direct or indirect communication between tissues.