In the present study, the shorter life span and down-regulation of defense-related genes in the S. Typhimurium infected mutant worms (cat-2) suggest a role of the IGF-1/DAF-16 and innate immune signaling pathways mediated by dopamine in the nematode resistance, which is consistent with the report that C. elegans may use a neuronal circuit to regulate protective functions via longevity and innate immune signaling pathways to combat bacterial infection when encountered with bacterial pathogens. Here, IGF1 is linked to bacterial infectious disease.