The role of complement in the acquired immune response

Immunology. 2000 May;100(1):4-12. doi: 10.1046/j.1365-2567.2000.00009.x.


Studies over the past three decades have clearly established a central role for complement in the promotion of a humoral immune response. The primary function of complement, in this regard, is to opsonize antigen or immune complexes for uptake by complement receptor type 2 (CR2, CD21) expressed on B cells, follicular dendritic cells (FDC) and some T cells. A variety of mechanisms appear to be involved in complement-mediated promotion of the humoral response. These include: enhancement of antigen (Ag) uptake and processing by both Ag-specific and non-specific B cells for presentation to specific T cells; the activation of a CD21/CD19 complex-mediated signalling pathway in B cells, which provides a stimulus synergistic to that induced by antigen interaction with the B-cell receptor (BCR); and promotion of the interaction between B cells and FDC, where C3d-bearing immune complexes participate in intercellular bridging. Finally, current studies suggest that CR2 may also play a role in the determination of B-cell tolerance towards self-antigens and thereby hold the key to the previously observed correlation between deficiencies of the early complement components and autoimmune disease.

Publication types

  • Review

MeSH terms

  • Antibody Formation / immunology*
  • Antigen Presentation / immunology
  • B-Lymphocytes / immunology
  • Complement System Proteins / immunology*
  • Dendritic Cells, Follicular / immunology
  • Humans
  • Immune Tolerance
  • Lymphocyte Activation / immunology


  • Complement System Proteins