C3D OF COMPLEMENT AS A MOLECULAR ADJUVANT - BRIDGING INNATE AND ACQUIRED-IMMUNITY

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