Evidence That Human Fcγ Receptor IIA (CD32) Subtypes Are Not Receptors for Oxidized LDL

Abstract Several lines of evidence suggest that clearance of oxidized LDL (oxLDL) immune complexes by macrophage IgG Fc receptors (FcγRs) plays a role in atherogenesis. OxLDL may also be cleared directly by FcγRs, as shown for murine FcγRII-B2. In humans, the homologous FcγR is FcγRIIA (CD32), which is abundantly expressed on monocytes and macrophages and shares 60% sequence identity with murine FcγRII-B2. As murine FcγRII-B2 and human FcγRIIA also share similar IgG ligand-binding properties, the purpose of this study was to test the hypothesis that human CD32 is a receptor for oxLDL. For these studies we used transfected Chinese hamster ovary (CHO) cells, monocytes, and cell lines that functionally express either of two FcγRIIA subtypes (R131 or H131) and assayed binding or degradation of several preparations of oxLDL. The integrity of all oxLDL preparations was checked by studying their ability to react with CHO cells expressing human type I scavenger receptors and by other characteristics of lipoprotei...