Co-cross-linking of surface immunoglobulin Fcγ receptors on B lymphocytes uncouples the antigen receptors from their associated G protein
✍ Scribed by Kevin P. Rigley; Margaret M. Harnett; G. B. Klaus
- Publisher
- John Wiley and Sons
- Year
- 1989
- Tongue
- English
- Weight
- 524 KB
- Volume
- 19
- Category
- Article
- ISSN
- 0014-2980
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✦ Synopsis
Co-cross-linking of surface immunoglobulin Fcy receptors on B lymphocytes uncouples the antigen receptors from their associated G protein
Cross-linking of surface Ig receptors (sIg) by mitogenic forms of anti-Ig antibodies (e.g. F(ab')2 fragments of rabbit anti-Ig) causes the rapid, and prolonged breakdown of phosphatidylinositol 4,5-bisphosphate. This response involves an unidentified guanine nucleotide regulatory protein (termed G,), which couples sIg to the polyphosphoinositide-specific phosphodiesterase. Intact (IgG) rabbit anti-Ig antibodies, which co-cross-link sIg and Fcy receptors on B cells, only induce short-lived inositol phospholipid breakdown and abortive B cell activation. We show here that in permeabilized B cells intact anti-Ig inhibits the reconstituted breakdown of inositol phospholipids given by a combination of F(ab')2 anti-Ig and the non-hydrolyzable GTP analogue guanosine-5'-0-(3-thiiotriphosphate) (GTPyS), but not the basal stimulation of G, induced by GTPyS alone. These results therefore indicate that cocross-linkage of sIg and Fcy receptors on B cells uncouples the antigen receptors from the associated G protein, but does not affect coupling between G, and the phosphodiesterase. These observations therefore provide further insight into the mechanisms whereby engaging Fc receptors on B cells, by antigen-antibody complexes for example, could modulate antigen-induced B cell activation.