The Toll/interleukin-1 receptor (TIR) homology domain is an intracellular signalling domain found in MyD88, interleukin 1 receptor and the Toll receptor. It contains three highly-conserved regions, and mediates protein-protein interactions between the Toll-like receptors (TLRs) and signal-transduction components. TIR-like motifs are also found in plant proteins thought to be involved in resistance to disease. When activated, TIR domains recruit cytoplasmic adaptor proteins MyD88 (Swiss:Q99836) and TOLLIP (Toll interacting protein, Swiss:Q9H0E2). In turn, these associate with various kinases to set off signalling cascades [3].

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2: A human homologue of the Drosophila Toll protein signals activation of adaptive immunity [see comments] Medzhitov R, Preston-Hurlburt P, Janeway CA Jr; Nature 1997;388:394-397. PMID:9237759

3: Toll-like receptors: a family of pattern-recognition receptors in mammals. Armant MA, Fenton MJ; Genome Biol 2002;3:REVIEWS3011. PMID:12186654