TLR4 and infection: In the Toll immune pathway, Spaetzle is activated by the hydrolysis of an aminoprotease cascade protein upon infection and binds to the transmembrane receptor Toll, leading to the phosphorylation and degradation of the IκB factor Cactus and the nuclear translocation of NF-κB family members Dorsal or Dif, which induce the expressions of downstream antimicrobial peptides (AMPs) such Drosomycin (Drs) and Metchnikowin (Mtk) (Fitzgerald & Kagan, 2020).