Macrophage receptor that binds to the apolipoprotein B48 (APOB) of dietary triglyceride (TG)-rich lipoproteins (TRL) or to a like domain of APOB in hypertriglyceridemic very low density lipoprotein (HTG-VLDL). Binds and internalizes TRL when out of the context of the macrophage. May provide essential lipids to reticuloendothelial cells. Could also be involved in foam cell formation with elevated TRL and remnant lipoprotein (RLP). Mediates the rapid high-affinity uptake of chylomicrons (CM), HTG-VLDL, and trypsinized (tryp) VLDL devoid of APOE in vitro in macrophages. Homodimer. Binds monocyte-macrophage membrane. Thought to be anchored in the membrane through an interaction with an integral membrane protein. Expressed in peripheral blood leukocytes > bone marrow = spleen > lymph node, and only faintly visible in appendix and thymus. Expressed in the brain, heart, kidney, liver, lung, pancreas, and placenta. Expressed primarily by reticuloendothelial cells: monocytes, macrophages, and endothelial cells. Expressed in atherosclerotic lesion foam cells. Suppressed significantly by PPARA and PPARG in THP-1 and blood-borne monocyte-macrophages. Decreased after pitavastatin treatment in peripheral blood macrophages and remnant lipoprotein (RLP)-induced foam cell formation. There are 2 forms in macrophages, the membrane-binding proteins 200 kDa (MBP 200) and 235 kDa (MBP 235), that can be reduced into a single active ligand-binding species with intermediate mobility (MBP 200R).