From expression to signaling: Roles of TREM-1 and TREM-2 in innate immunity and bacterial infection

Triggering receptor expressed on myeloid cells (TREM) proteins play important roles in innate and adaptive immunity. Since the discovery of TREM-1 and TREM-2 in 2000, the field has exploded over the past 8 years and currently TREM-1 is thought of as an amplifier of the immune response, while TREM-2 is believed to be a negative regulator. Here, we discuss the current state of the literature on TREMs, with a focus on TREM-1 and TREM-2 and their expression, signaling in mononuclear phagocytes and roles in innate immunity and bacterial infection.