ABSTRACT
This chapter explores the information on complement activation-related pseudoallergy, accelerated blood clearance (ABC phenomenon), and immunosuppression; highlights their common and specific causes; and discusses their mechanisms. The immune effects of liposomes can be stimulatory or inhibitory, weak, moderate or severe, all with a broad individual variation in the time of onset and duration. In addition to viruses, liposomes also resemble ectosomes, i.e., membrane vesicles detached from cells, as well as most other ecto-organelles and cellular debris that form upon cell death. Nanobacteria, the smallest self-replicating pathogens, are also in the liposome size range. Acute hypersensitivity reactions to liposomes have been reported from time to time, ever since 1986, the first clinical study wherein large doses of liposomes were infused in cancer patients. Being built from natural, or natural-like (regarding stereochemistry and composition), synthetic or semisynthetic phospholipids, liposomes are generally not immunogenic.
