Quantitative proteomics identifies ferritin in the innate immune response of C. elegans.

When encountering a pathogen, all organisms evoke a protective response by inducing defense mechanisms to help fight off the invader. The invertebrate model organism Caenorhabditis elegans has proven to be valuable for studies of the host response and the small nematode mounts a substantial transcriptional response to numerous pathogens. Here, we use global quantitative proteomics to profile the response to infection with E. coli strain LF82 isolated from patients suffering from Crohn's disease, an inflammatory bowel disease. We show that LF82 infection induces more than one hundred proteins. The response share many functional categories with other innate immunity studies in C. elegans, but also identifies novel host immune effector proteins. We demonstrate functional relevance for four LF82 induced proteins, including a lysozyme and a C-type lectin. The ferritin homolog FTN-2 was shown to be necessary for the full protective response against the Gram-negative LF82 and the Gram-positive pathogen Staphylococcus aureus. This study is the first to demonstrate a role for ferritin in the innate immune response of C. elegans, and our results suggests that quantitative proteomics is an attractive approach for identifying additional components in the complex immune response of the nematode.