IgM and stromal cell-associated heparan sulfate / heparin as complement-independent ligands for CD19
✍ Scribed by Antonin R. de Fougerolles; Facundo Batista; Eskil Johnsson; Douglas T. Fearon
- Publisher
- John Wiley and Sons
- Year
- 2001
- Tongue
- English
- Weight
- 248 KB
- Volume
- 31
- Category
- Article
- ISSN
- 0014-2980
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✦ Synopsis
The more severe phenotype of mice lacking CD19 as compared to CD21 suggests that a complement-independent ligand for the CD19/CD21 complex exists. We sought ligands for CD19 by examining binding reactions with fusion proteins comprised of the extracellular region of CD19 and the Fc region of IgG1. A fusion protein containing the third extracellular domain (D3-Fc) bound to WEHI-231 cells, and this was competed by soluble IgM. This function of IgM was confirmed by the binding of D3-Fc to beads coated with IgM. A second ligand for D3-Fc was found on stromal cells, and was shown to be heparin/heparan sulfate. These two ligands would be considered to reside on follicular dendritic cells, and may account for the observed ability of D3-Fc to bind to sites in germinal centers containing these cells.