Cellular and Organismal Responses to Infections in Caenorhabditis elegans

The nematode Caenorhabditis elegans has emerged as a powerful model system to study cellular responses to microbial infections in the context of a whole animal. Like other free-living nematodes, the one-millimeter-long nematode C. elegans lives in the soil and on rotting fruit, where it is in contact with several microbes, including human microbial pathogens. While it lacks an adaptive immune system and professional phagocytes involved in defense against pathogens, it possesses mechanisms to recognize different microbes and to respond accordingly. C. elegans does not seem to have conserved pattern recognition receptors (PRRs) for pathogen detection through known microbe-associated molecular patterns (MAMPs). Still, it can recognize pathogen attacks through different mechanisms, including the neuronal sensation of bacterial cues and detection of disturbances of cellular homeostasis. The immune response mounted by C. elegans upon pathogen infection comprises evolutionarily conserved signaling pathways that result in avoidance of pathogens and the induction of immune effector mechanisms to combat infections.