The Toll-like receptor (TLR) family in mammal comprises a family of trans-membrane proteins characterized by multiple copies of leucine rich repeats in the extracellular domain and 1L-1 receptor motif in the cytoplasmic domain. Like its counterparts in Drosophila, TLRs signal through adaptor molecules. The TLR family is a phylo-genetically conserved mediator of innate immunity that is essential for microbial recognition. Ten human homologs of TLRs (TLR1-10) have been described. Amount this family of receptors, TLR2 and TLR4 have been most studied. These studies have suggested that TLR2 and TLR4 may serve as potential main mediatiors of LPS signaling. The mouse TLR4 cDNA codes for a protein consisting of 839 amino acids, with an approximate molecular weight of 90kD.