Description: The GD2.F4 antibody reacts with human Toll-like receptor 1 (TLR1). TLR1 is expressed in low numbers on the surface of peripheral blood monocytes and even lower numbers on dendritic cells. A very high degree of donor variability has been reported for TLR1 expression. eBioscience manufactured GD2.F4 mAb has been tested by flow cytometry, in parallel with a sample from the developer using cells from healthy donors. eBioscience and the reference antibody gave similar results: donors tested confirmed low levels expression of TLR1 on PBMC (less than 1/4 log shift). While the ligand and exact function of TLR1 are not defined yet, it has been suggested that TLR1 may cooperate with TLR2 in response to certain antagonists. Despite low levels of surface expression as detected by flow cytometric analysis, TLRs are efficient signal transducing molecules in monocytes and dendritic cells. To date, at least ten members of the Toll family have been identified in human. This family of type I transmembrane proteins is characterized by an extracellular domain with leucine-rich repeats and a cytoplasmic domain with homology to the type I IL-1 receptor. Two of these receptors, TLR2 and TLR4, are pattern recognition receptors and signaling molecules in response to bacterial lipoproteins and have been implicated in innate immunity and inflammation.