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Biomaterials. 2014 Apr;35(11):3688-96. doi: 10.1016/j.biomaterials.2013.12.085. Epub 2014 Jan 23.

Mediation of a non-proteolytic activation of complement component C3 by phospholipid vesicles.

Author information

1
Institute of Applied Physics and Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), Wolfgang-Gaede-Str. 1, 76131 Karlsruhe, Germany; Carl Gustav Carus-Institute, Association for the Promotion of Cancer Therapy, Am Eichhof 30, 75223 Niefern-Öschelbronn, Germany; Department of Immunology, Genetics and Pathology, Rudbeck Laboratory C5:3, Uppsala University, 75185 Uppsala, Sweden.
2
Department of Immunology, Genetics and Pathology, Rudbeck Laboratory C5:3, Uppsala University, 75185 Uppsala, Sweden.
3
Department of Immunology, Genetics and Pathology, Rudbeck Laboratory C5:3, Uppsala University, 75185 Uppsala, Sweden; Department of Bioengineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo 113-8656, Japan.
4
Carl Gustav Carus-Institute, Association for the Promotion of Cancer Therapy, Am Eichhof 30, 75223 Niefern-Öschelbronn, Germany.
5
Institute of Applied Physics and Center for Functional Nanostructures (CFN), Karlsruhe Institute of Technology (KIT), Wolfgang-Gaede-Str. 1, 76131 Karlsruhe, Germany; Department of Physics, University of Illinois at Urbana-Champaign, 1110 W. Green Street, Urbana, IL 61801, USA; Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
6
Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
7
Department of Immunology, Genetics and Pathology, Rudbeck Laboratory C5:3, Uppsala University, 75185 Uppsala, Sweden; Linnæus Center of Biomaterials Chemistry, Linnæus University, 39182 Kalmar, Sweden.
8
Department of Immunology, Genetics and Pathology, Rudbeck Laboratory C5:3, Uppsala University, 75185 Uppsala, Sweden. Electronic address: bo.nilsson@igp.uu.se.

Abstract

Liposomes are becoming increasingly important as drug delivery systems, to target a drug to specific cells and tissues and thereby protecting the recipient from toxic effects of the contained drug. Liposome preparations have been described to activate complement. In this study, we have investigated complement activation triggered by neutral dimyristoyl-phosphocholine (DMPC) liposomes in human plasma and whole-blood systems. Incubation in plasma led to the generation of complement activation products (C3a and sC5b-9). Unexpectedly, investigations of surface-bound C3 revealed contact activated, conformationally changed C3 molecules on the liposomes. These changes were characterized by Western blotting with C3 monoclonal antibodies, and by incubating liposomes with purified native C3 and factors I and H. Quartz crystal microbalance analysis confirmed binding of C3 to planar DMPC surfaces. In addition, we demonstrated that DMPC liposomes bound to or were phagocytized by granulocytes in a complement-dependent manner, as evidenced by the use of complement inhibitors. In summary, we have shown that C3 is activated both by convertase-dependent cleavage, preferentially in the fluid phase, by mechanisms which are not well elucidated, and also by contact activation into C3(H2O) on the DMPC surface. In particular, this contact activation has implications for the therapeutic regulation of complement activation during liposome treatment.

KEYWORDS:

Complement; Contact activation; Immune response; Liposome

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