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Annu Rev Immunol. 2000;18:393-422.

Regulation of B lymphocyte responses to foreign and self-antigens by the CD19/CD21 complex.

Author information

1
Wellcome Trust Immunology Unit, Department of Medicine, School of Clinical Medicine, University of Cambridge, United Kingdom. dtf1000@cus.cam.ac.uk

Abstract

The membrane protein complex CD19/CD21 couples the innate immune recognition of microbial antigens by the complement system to the activation of B cells. CD21 binds the C3d fragment of activated C3 that becomes covalently attached to targets of complement activation, and CD19 co-stimulates signaling through the antigen receptor, membrane immunoglobulin. CD21 is also expressed by follicular dendritic cells and mediates the long-term retention of antigen that is required for the maintenance of memory B cells. Understanding of the biology of this receptor complex has been enriched by analyses of genetically modified mice; these analyses have uncovered roles not only in positive responses to foreign antigens, but also in the development of tolerance to self-antigens. Studies of signal transduction have begun to determine the basis for the coreceptor activities of CD19. The integration of innate and adaptive immune recognition at this molecular site on the B cell guides the appropriate selection of antigen by adaptive immunity and emphasizes the importance of this coreceptor complex.

[Indexed for MEDLINE]

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