Triggering Receptor Expressed on Myeloid Cells 1 (TREM-1) is a transmembrane protein with a single Ig-like domain. TREM-1 associates with the adapter protein, DAP12, to deliver an activating signal. TREM-1 is expressed on blood neutrophils and monocytes, and the expression is up-regulated by bacterial LPS. TREM-1 is expressed at high levels on neutrophils of patients with microbial sepsis and in mice with a TREM-1/Fc fusion protein protected mice against LPS-induced shock. It stimulates neutrophil and monocyte-mediated inflammatory responses. Triggers release of pro-inflammatory chemokines and cytokines, as well as increased surface expression of cell activation markers. TREM-1 is amplifier of inflammatory responses that are triggered by bacterial and fungal infections and are a crucial mediator of septic shock.