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Neonatal Fc receptor for IgG (FcRn) regulates cross-presentation of IgG immune complexes by CD8-CD11b+ dendritic cells.

ABSTRACT: Cross-presentation of IgG-containing immune complexes (ICs) is an important means by which dendritic cells (DCs) activate CD8(+) T cells, yet it proceeds by an incompletely understood mechanism. We show that monocyte-derived CD8(-)CD11b(+) DCs require the neonatal Fc receptor for IgG (FcRn) to conduct cross-presentation of IgG ICs. Consequently, in the absence of FcRn, Fc? receptor (Fc?R)-mediated antigen uptake fails to initiate cross-presentation. FcRn is shown to regulate the intracellular sorting of IgG ICs to the proper destination for such cross-presentation to occur. We demonstrate that FcRn traps antigen and protects it from degradation within an acidic loading compartment in association with the rapid recruitment of key components of the phagosome-to-cytosol cross-presentation machinery. This unique mechanism thus enables cross-presentation to evolve from an atypically acidic loading compartment. FcRn-driven cross-presentation is further shown to control cross-priming of CD8(+) T-cell responses in vivo such that during chronic inflammation, FcRn deficiency results in inadequate induction of CD8(+) T cells. These studies thus demonstrate that cross-presentation in CD8(-)CD11b(+) DCs requires a two-step mechanism that involves Fc?R-mediated internalization and FcRn-directed intracellular sorting of IgG ICs. Given the centrality of FcRn in controlling cross-presentation, these studies lay the foundation for a unique means to therapeutically manipulate CD8(+) T-cell responses.

SUBMITTER: Baker K

PROVIDER: S-EPMC3116387 | biostudies-literature | 2011 Jun

REPOSITORIES: biostudies-literature

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Neonatal Fc receptor for IgG (FcRn) regulates cross-presentation of IgG immune complexes by CD8-CD11b+ dendritic cells.

Baker Kristi K Qiao Shuo-Wang SW Kuo Timothy T TT Aveson Victoria G VG Platzer Barbara B Andersen Jan-Terje JT Sandlie Inger I Chen Zhangguo Z de Haar Colin C Lencer Wayne I WI Fiebiger Edda E Blumberg Richard S RS

Proceedings of the National Academy of Sciences of the United States of America 20110531 24

Cross-presentation of IgG-containing immune complexes (ICs) is an important means by which dendritic cells (DCs) activate CD8(+) T cells, yet it proceeds by an incompletely understood mechanism. We show that monocyte-derived CD8(-)CD11b(+) DCs require the neonatal Fc receptor for IgG (FcRn) to conduct cross-presentation of IgG ICs. Consequently, in the absence of FcRn, Fcγ receptor (FcγR)-mediated antigen uptake fails to initiate cross-presentation. FcRn is shown to regulate the intracellular so ...[more]

PMID: 21628593

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Project description:Preclinical and clinical studies have established that autoreactive immunoglobulin G (IgG) can drive neuropathic pain. We recently demonstrated that sciatic nerve chronic constriction injury (CCI) in male and female mice results in the production of pronociceptive IgG, which accumulates around the lumbar region, including within the dorsal root ganglia (DRG) and spinal cord, facilitating the development of neuropathic pain. These data raise the intriguing possibility that neuropathic pain may be alleviated by reducing the accumulation of IgG. To this end, we tested whether biologic inhibition or genetic deletion of the neonatal Fc receptor (FcRn) would attenuate mechanical hypersensitivity (allodynia) and IgG deposition induced by CCI. FcRn are prominently expressed on myeloid and endothelial cells and extend the half-life of IgG via pinocytosis and recycling into the extracellular milieu. We show here that administration of the FcRn blocker efgartigimod either 7- or 28-days post-CCI relieved allodynia among both male and female mice, compared to the Fc fragment control. Efgartigimod, administered systemically (intraperitoneal) or to the lumbar region (intrathecal), attenuated mechanical allodynia for at least one month. CCI-induced allodynia was similarly reduced in FcRn-deficient (FcRn-) mice compared to wild-type mice. Biologic inhibition or genetic deletion of FcRn also reduced CCI-induced accumulation of IgG on macrophages and neurons in lumbar DRG, as well as microglia in the lumbar dorsal spinal cord. Expression of the Fc receptor γ subunit (FcRγ) was reduced in efgartigimod-treated or FcRn- mice post-CCI compared to controls. The FcRγ subunit is a key component of Fc gamma receptors (FcγRs), which are activated by IgG immune complexes. In macrophage cultures stimulated by IgG immune complexes, FcRn blockade also dampened FcγR-dependent production of proinflammatory cytokines. Collectively, our study demonstrates that FcRn blockade or deletion alleviates mechanical allodynia and reduces IgG accumulation after CCI, attenuating pronociceptive IgG-FcγR signaling around the lumbar region. Strategies to block FcRn and reduce IgG recycling warrant further investigation as potential treatments for IgG-mediated neuropathic pain.

Dataset Information

Neonatal Fc receptor for IgG (FcRn) regulates cross-presentation of IgG immune complexes by CD8-CD11b+ dendritic cells.

Publications

Neonatal Fc receptor for IgG (FcRn) regulates cross-presentation of IgG immune complexes by CD8-CD11b+ dendritic cells.

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