A macrophage Fc receptor for IgG is also a receptor for oxidized low density lipoprotein

Abstract

The internalization of oxidized low density lipoprotein (OxLDL) by macrophages is hypothesized to contribute to foam cell formation and eventually to atherosclerotic lesion formation. OxLDL is a ligand for the acetylated low density lipoprotein (AcLDL) receptor, however, our data show that this receptor accounts for less than half of OxLDL uptake by mouse macrophages, suggesting additional receptors for OxLDL. We have developed a novel expression cloning strategy in order to isolate clones encoding OxLDL receptors. In addition to the AcLDL receptor, we isolated a molecular clone for a structurally unrelated receptor capable of mediating the high affinity uptake of OxLDL following transfection into cells. This receptor has been identified as the mouse Fc gamma RII-B2, a member of a family of receptors known to mediate immune complex uptake through recognition of the Fc region of IgG. The uptake of OxLDL by cells transfected with the Fc gamma RII-B2 clone is not blocked by AcLDL but is blocked by the anti-Fc gamma RII monoclonal antibody, 2.4G2.