C3d of Complement as a Molecular Adjuvant: Bridging Innate and Acquired Immunity

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Science  19 Jan 1996:
Vol. 271, Issue 5247, pp. 348-350
DOI: 10.1126/science.271.5247.348


An optimal immune response should differentiate between harmful and innocuous antigens. Primitive systems of innate immunity, such as the complement system, may play a role in this distinction. When activated, the C3 component of complement attaches to potential antigens on microorganisms. To determine whether this alters acquired immune recognition, mice were immunized with a recombinant model antigen, hen egg lysozyme (HEL), fused to murine C3d. HEL bearing two and three copies of C3d was 1000- and 10,000-fold more immunogenic, respectively, than HEL alone. Thus, C3d is a molecular adjuvant of innate immunity that profoundly influences an acquired immune response.

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