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Updated: May 19, 2026

Methods for Quantitative Detection of Antibody-induced Complement Activation on Red Blood Cells
Published on: January 29, 2014
Regulation of humoral immunity by complement
Michael C Carroll1, David E Isenman
1Immune Disease Institute and Program in Molecular and Cellular Medicine, Children's Hospital and Department of Pediatrics, Harvard Medical School, Boston, 02115 MA, USA. carroll@idi.harvard.edu
Abstract:
The complement system of innate immunity is important in regulating humoral immunity largely through the complement receptor CR2, which forms a coreceptor on B cells during antigen-induced activation. However, CR2 also retains antigens on follicular dendritic cells (FDCs). Display of antigen on FDCs is critical for clonal selection and affinity maturation of activated B cells. This review will discuss the role of complement in adaptive immunity in general with a focus on the interplay between CR2-associated antigen on B cells with CR2 expressed on FDCs. This latter interaction provides an opportunity for memory B cells to sample antigen over prolonged periods. The cocrystal structure of CR2 with its ligand C3d provides insight into how the complement system regulates access of antigen by B cells with implications for therapeutic manipulations to modulate aberrant B cell responses in the case of autoimmunity.
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