The triggering receptor expressed on myeloid cells-1 (TREM-1), a member of the immunoglobulin superfamily, is upregulated on phagocytic cells in the presence of bacteria or fungi infection and weakly expressed in samples from patients with noninfectious inflammatory disorders. In addition, TREM-1 is shed from the membrane of activated phagocytes and can be found in a soluble form (sTREM-1) in body fluids. The level and serial change of a serum sTREM-1 from cirtical ill patients has been shown to be a good diagnostic and prognostic indicator of ventilation associated pneumonia (VAP) and severe sepsis.