Cell surface receptor that plays important roles in innate and adaptive immunity by amplifying inflammatory responses (PubMed:10799849, PubMed:21393102). Upon activation by various ligands such as PGLYRP1, HMGB1 or HSP70, multimerizes and forms a complex with transmembrane adapter TYROBP/DAP12 (PubMed:25595774, PubMed:17568691, PubMed:29568119). In turn, initiates a SYK-mediated cascade of tyrosine phosphorylation, activating multiple downstream mediators such as BTK, MAPK1, MAPK3 or phospholipase C-gamma (PubMed:21659545, PubMed:14656437). This cascade promotes the neutrophil- and macrophage-mediated release of pro-inflammatory cytokines and/or chemokines, as well as their migration and thereby amplifies inflammatory responses that are triggered by bacterial and fungal infections (PubMed:17568691, PubMed:17098818). By also promoting the amplification of inflammatory signals that are initially triggered by Toll-like receptor (TLR) and NOD-like receptor engagement, plays a major role in the pathophysiology of acute and chronic inflammatory diseases of different etiologies including septic shock and atherosclerosis (PubMed:21393102, PubMed:11323674). Acts as a decoy receptor, counterbalancing TREM1 pro-inflammatory activity through the neutralization of its lignad. Monomer (PubMed:29568119). Homomultimer; when activated (PubMed:29568119). Interacts with TYROBP/DAP12 (PubMed:10799849, PubMed:15351648). Interacts with TLR4 (PubMed:17098818, PubMed:21393102). Recruited to lipid rafts when activated. Mostly expressed by immune cells of the myeloid lineage, such as monocytes, macrophages, neutrophils and dendritic cells (PubMed:10799849). Expression is associated with a mature stage of myeloid development (PubMed:11922939). Highly expressed in adult liver, lung and spleen than in corresponding fetal tissue. Also expressed in the lymph node, placenta, spinal cord and heart tissues. Isoform 2 was detected in the lung, liver and mature monocytes. Up-regulated by bacteria, fungi and bacterial lipopolysaccharides (LPS). Glycosylated.