The Toll/Toll-like receptor (TLR) family members are type-I single-pass transmembrane receptors with an intracellular Toll IL-1R homology (TIR) domain and extracellular Leucine-rich repeats. The archetypal family member, Tl, was first characterized for its role in embryonic dorsal/ventral patterning. In larval and adult stages, Tl is involved with innate immune response. Tl is activated by binding an endogenous spatzle ligand and activation of NF-κB is the target of canonical Toll/Toll-like receptor signaling. Non-canonical signaling pathways are less well characterized. (Adapted from FBrf0130108, FBrf0212564 and FBrf0239503).