Liposome-mediated triggering of complement cascade

The complement system is one of the most ancient defense strategies, which serves as an important effector arm of both innate and acquired immunity. Three consequences ensue when liposomes trigger the complement system in the blood. These are priming of the vesicular surface by opsonic complement fragments for recognition and clearance by phagocytic cells, generation of anaphylatoxins, and chemoattractants, which may subsequently initiate pseudoallergy-related anaphylaxis in sensitive individuals, and insertion of the lytic complex C5b-9 into the liposomal bilayer, which may result in substantial leakage of vesicular encapsulated aqueous cargo. Here, we briefly review and discuss the molecular basis of complement activation by phospholipid vesicles and reflect on sensitive and rapid Enzyme-Linked Immunosorbent Assays (ELISA) for assessing and monitoring liposome-mediated triggering of a complement cascade in human serum.