Abstract
PEG has been believed a bio-inert polymer which increases bioavailability of therapeutic protein or nanocarrier and decreases immunogenicity of them. PEGylation is still a golden standard in developing protein therapeutic or nanocarrier system. However, we and other groups have reported that PEGylated liposomes or PEGylated proteins induce immune responses against PEG and subsequently produce anti-PEG antibodies, resulting in rapid clearance of second dose PEGylated materials via complement activation. Such immunological responses against PEG should be dependent on animal species to which PEGylated materials are injected. Adverse effects, which might occur during the ABC phenomenon, also should be dependent on animal species. Although there are a few publications regarding effect of animal species on the ABC phenomenon, we try to introduce this issue with our speculation and consideration.
