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Biochem Soc Trans. 2003 Feb;31(Pt 1):281-5.

Fc gamma RIIB activation leads to inhibition of signalling by independently ligated receptors.

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Integrated Department of Immunology, National Jewish Medical and Research Center and University of Colorado Health Sciences Center, 1400 Jackson Street, Denver, CO 80206, USA.


The inhibitory IgG receptor, Fc gamma RIIB, blocks signalling by co-aggregated antigen receptors on mature and activated B-cells. Fc gamma RIIB is also expressed by immature B-cells; however, its function on these cells has not been defined. In the present paper, we demonstrate that immature B-cells are highly sensitive to inhibitory signalling mediated by Fc gamma RIIB. Co-aggregation of Fc gamma RIIB with the B-cell antigen receptor (BCR) on immature B-cells leads to near ablation of late phase calcium mobilization. Concomitant with enhanced inhibitory signalling, we found that Src-homology-2-domain-containing inositol 5'-phosphatase (SHIP) is expressed at much higher levels in immature B-cells than in mature B-cells. Perhaps most importantly, we report that SHIP activated by BCR-Fc gamma RIIB co-aggregation inhibits independently ligated receptors whose signalling requires PtdIns(3,4,5) P (3). We found that stromal-derived factor 1 (SDF-1)-induced cell migration is impaired by prior activation of Fc gamma RIIB. This inhibition is reduced in SHIP-deficient B-cells. Therefore receptor-mediated signalling responses that are dependent on PtdIns(3,4,5) P (3) are subject to both direct and indirect inhibition by Fc gamma RIIB-activated SHIP.

[Indexed for MEDLINE]

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