Novel anti-cholesterol monoclonal immunoglobulin G antibodies as probes and potential modulators of membrane raft-dependent immune functions

Adrienn Bíró¹^,*^,, László Cervenak¹^,, Andrea Balogh¹^,, András L $o$ rincz, Katalin Uray^**, Anna Horváth^*, László Romics^*^,, János Matkó, George Füst^*^, and Glória László²^,

^* Third Department of Internal Medicine, Research Laboratory, Semmelweis University, Budapest, Hungary
Research Group on Metabolism and Atherosclerosis, Hungarian Academy of Sciences-Semmelweis University, Budapest, Hungary
Department of Immunology, Eötvös Lorand University, Budapest, Hungary
^** Department of Organic Chemistry, Eötvös Lorand University, Budapest, Hungary

Published, JLR Papers in Press, October 5, 2006.

^¹ A. Bíró, L. Cervenak, and A. Balogh contributedequally to this work.

^² To whom correspondence should be addressed. e-mail: glorial{at}elte.hu

Natural autoantibodies against cholesterol are present in thesera of all healthy individuals; their function, production,and regulation, however, are still unclear. Here, we managedto produce two monoclonal anti-cholesterol antibodies (ACHAs)by immunizing mice with cholesterol-rich liposomes. The newACHAs were specific to cholesterol and to some structurallyclosely related 3ß-hydroxyl sterols, and they reactedwith human lipoproteins VLDL, LDL, and HDL. They bound, usuallywith low avidity, to live human or murine lymphocyte and monocyte-macrophagecell lines, which was enhanced substantially by a moderate papaindigestion of the cell surface, removing some protruding extracellularprotein domains. Cell-bound ACHAs strongly colocalized withmarkers of cholesterol-rich lipid rafts and caveolae at thecell surface and intracellularly with markers of the endoplasmicreticulum and Golgi complex. These data suggest that these IgGACHAs may serve as probes of clustered cholesterol (e.g., differentlipid rafts) in live cells and thus may also have immunomodulatorypotential.

Supplementary key words membrane cholesterol • lymphocytes • monocyte-macrophage cells • lipoproteins • lipid rafts • caveolae

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