TLR5 is an ~100kD type I transmembrane glycoprotein of the Toll-like receptor family. It is expressed on mucosal epithelia in the gastrointestinal tract, airways, and other areas of potential bacterial contact and recognizes bacterial flagellin. Expression is also reported on monocytes, immature dendritic cells, and CD4+ T lymphocytes. The region of human TLR5 used as an immunogen includes the first 2 of 16 leucine-rich repeats and shares 72% aa identity with mouse and rat TLR5. This region is outside of the flagellin binding region. Flagellin engagement induces dimerization and intracellular signaling via MyD88.