Previous studies have shown that three major highly conserved signal transduction pathways, the nsy-1/sek-1/pmk-1 p38 MAP kinase pathway, the daf-2/daf-16 insulin/IGF1 pathway and the dbl-1/TGF-β signaling pathway, play significant roles in the survival of the host during infection (Kim et al., 2002; Mallo et al., 2002; Garsin et al., 2003). This evidence concerns the gene MAP2K4 and infection.