Toll-like receptors (TLRs) are type I transmembrane signaling receptors characterized by containing leucine-rich repeats (LRR) extracellular domain and IL-1 receptor like intracellular domain. TLRs are responsible for recognizing pathogen-associated molecule patterns (PAMPs). They are primary sensors of both innate and adaptive immune systems. To date a total of 12 TLRs have been indentified. Toll-like receptor 1 (TLR1), known as CD281, is expressed on monocytes/macrophages, dendritic cells, and granulocytes and some lymphocytes at low levels. By association with TLR2, TLR1 is a coreceptor involved in the response to diverse set of pathogens, such as triacylated lipopeptidess (but not diacylated lipopeptides), peptidoglycans, lipoteichoic acid. The GD2.F4 antibody can be used for flow cytometry and for neutralization of TLR1.