International Immunology, Vol. 14, No. 10, pp. 1179-1191,
October 2002
© 2002 Japanese Society for Immunology
Cooperative interaction of Ig
and Igß of the BCR regulates the kinetics and specificity of antigen targeting
1 Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA 2 Section of Rheumatology, Department of Medicine, University of Chicago, IL 60637, USA
Correspondence to: W. Song; E-mail: ws98{at}umail.umd.edu
Transmitting editor: L. H. Glimcher
Following the binding of antigens, the BCR transduces signals and internalizes antigens for processing and presentation, both of which are required for initiating an effective antibody response. The BCR, consisting of membrane Ig and Ig
/Igß heterodimer, facilitates antigen processing by accelerating antigen targeting to the processing compartment. Previous reports showed that Ig or Igß alone is competent for internalizing antigens. However, both Ig and Igß are required for BCR-enhanced antigen presentation. Using chimeric proteins containing the extracellular and transmembrane domains of human platelet-derived growth factor receptor fused with the cytoplasmic domain of Ig or Igß, we studied the roles of the cytoplasmic tails of Ig and Igß in BCR-mediated antigen transport. The Igß chimera rapidly moves through the endocytic pathway to lysosomes, while the Ig chimera slows down this movement. The Ig, but not the Igß chimera, is required for an increase in the turnover rate of the chimeras in response to stimulation. Only when Ig and Igß chimeras are co-expressed do the chimeras rapidly and specifically target antigens to the processing compartment. These findings suggest that Ig and Igß play distinct roles in BCR trafficking, and the cooperative interaction of Ig and Igß controls and regulates the kinetics and specificity of antigen targeting.
Keywords: antibody/antigen receptor, antigen processing, B lymphocytes, Ig/Igß heterodimer
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