The Toll-like receptor (TLR) family in mammals comprises a family of transmembrane proteins characterized by multiple copies of leucine rich repeats in the extracellular domain and IL-1 receptor motif in the cytoplasmic domain. Like its counterparts in Drosophila, TLRs signal through adaptor molecules. The TLR family is a phylogenetically conserved mediator of innate immunity that is essential for microbial recognition. Ten human homologs of TLRs (TLR1-10) have been described. TIRAP (TIR domain-containing adaptor protein) is an adaptor protein used by TLR4. Blocking TIRAP inhibits TLR4-mediated signaling events, including DC maturation and cytokine production.