TLR4 and infection: In Drosophila the Toll pathway is activated upon infection via the proteolytic cleavage of the cytokine Spätzle (Chasan and Anderson, 1989; Weber et al., 2003; Stein et al., 1991), which triggers a signal transduction cascade that leads to the nuclear translocation of the NFκB transcription factors Dorsal and Dif (Drier et al., 1999).