The TREM family of receptors regulates the activity of various cell types of the immune system including neutrophils, monocyte/macrophages, microglia, and dendritic cells. The receptors are members of the immunoglobulin superfamily, characterized structurally by a single V-set immunoglobulin (Ig) domain and a short cytoplasmic tail. TREMs associate with the DAP12 signal adapter, an immunoreceptor tyrosine-based activation motif- (ITAM)-containing protein that is phosphorylated and transduces signals when activated.