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Enhanced B-Cell Receptor Recognition of the Autoantigen Transglutaminase 2 by Efficient Catalytic Self-Multimerization.

Stamnaes J, Iversen R, du Pré MF, Chen X, Sollid LM - PLoS ONE (2015)

Bottom Line: The presence of exogenous substrate such as gluten peptide does not inhibit TG2 self-cross-linking, but rather results in formation of TG2-TG2-gluten complexes.TG2 multimers are superior to TG2 monomer in activating A20 B cells transduced with TG2-specific B-cell receptor, and uptake of TG2-TG2-gluten multimers leads to efficient activation of gluten-specific T cells.Importantly, high avidity of the antigen could explain why TG2-specific plasma cells show signs of an extrafollicular generation pathway.

View Article: PubMed Central - PubMed

Affiliation: Centre for Immune Regulation and Department of Immunology, University of Oslo and Oslo University Hospital, Oslo, Norway.

ABSTRACT
A hallmark of the gluten-driven enteropathy celiac disease is autoantibody production towards the enzyme transglutaminase 2 (TG2) that catalyzes the formation of covalent protein-protein cross-links. Activation of TG2-specific B cells likely involves gluten-specific CD4 T cells as production of the antibodies is dependent on disease-associated HLA-DQ allotypes and dietary intake of gluten. IgA plasma cells producing TG2 antibodies with few mutations are abundant in the celiac gut lesion. These plasma cells and serum antibodies to TG2 drop rapidly after initiation of a gluten-free diet, suggestive of extrafollicular responses or germinal center reactions of short duration. High antigen avidity is known to promote such responses, and is also important for breakage of self-tolerance. We here inquired whether TG2 avidity could be a feature relevant to celiac disease. Using recombinant enzyme we show by dynamic light scattering and gel electrophoresis that TG2 efficiently utilizes itself as a substrate due to conformation-dependent homotypic association, which involves the C-terminal domains of the enzyme. This leads to the formation of covalently linked TG2 multimers. The presence of exogenous substrate such as gluten peptide does not inhibit TG2 self-cross-linking, but rather results in formation of TG2-TG2-gluten complexes. The celiac disease autoantibody epitopes, clustered in the N-terminal part of TG2, are conserved in the TG2-multimers as determined by mass spectrometry and immunoprecipitation analysis. TG2 multimers are superior to TG2 monomer in activating A20 B cells transduced with TG2-specific B-cell receptor, and uptake of TG2-TG2-gluten multimers leads to efficient activation of gluten-specific T cells. Efficient catalytic self-multimerization of TG2 and generation of multivalent TG2 antigen decorated with gluten peptides suggest a mechanism by which self-reactive B cells are activated to give abundant numbers of plasma cells in celiac disease. Importantly, high avidity of the antigen could explain why TG2-specific plasma cells show signs of an extrafollicular generation pathway.

No MeSH data available.


Related in: MedlinePlus

Presentation of gluten peptide by TG2-specific B cells upon incubation with TG2-gluten peptide complexesA20 B cells expressing HLA-DQ2.5 alone or in combination with TG2-specific (679-14-E06) or non TG2-specific (693-2-F02) IgD BCR were incubated with size-fractionated complexes of TG2 and FITC-33mer peptide, and their ability to present deamidated peptide to DQ2.5-glia-α2-specific hybridoma T cells was assessed by measuring release of IL-2. When incubated with the free, deamidated peptide (33merE), all A20 cells were capable of presenting peptide to the T cells. Only TG2-specific cells, however, could take up and present complexes of TG2 and peptide.
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pone.0134922.g006: Presentation of gluten peptide by TG2-specific B cells upon incubation with TG2-gluten peptide complexesA20 B cells expressing HLA-DQ2.5 alone or in combination with TG2-specific (679-14-E06) or non TG2-specific (693-2-F02) IgD BCR were incubated with size-fractionated complexes of TG2 and FITC-33mer peptide, and their ability to present deamidated peptide to DQ2.5-glia-α2-specific hybridoma T cells was assessed by measuring release of IL-2. When incubated with the free, deamidated peptide (33merE), all A20 cells were capable of presenting peptide to the T cells. Only TG2-specific cells, however, could take up and present complexes of TG2 and peptide.

Mentions: Help from gluten-reactive T cells following B-cell uptake of TG2-gluten complexes is likely crucial for the development of the anti-TG2 response in celiac disease. As valency of TG2 had a clear impact on B-cell activation, we next addressed if this also is reflected in increased activation of gluten-specific T cells. Size-fractionated TG2 cross-linked in the presence of FITC labeled 33mer gluten peptide, which harbors multiple copies of the DQ2.5-glia-α2 epitope, was offered to the transduced A20 lymphoma cells and T-cell activation was assessed by IL-2 production of a T-cell hybridoma expressing T-cell receptor specific for the HLA-DQ2.5-glia-α2 epitope. When offering equal amounts of antigen (in μg TG2), TG2-33mer dimer and multimer were more effective at inducing IL-2 production than TG2-33mer monomer (Fig 6). Importantly, T-cell stimulation was dependent on BCR internalization as no T-cell proliferation was observed using TG2 multimers with non TG2-specific cells. Self-crosslinked TG2 multimers harboring gluten T-cell epitopes are thus highly potent B-cell activators that also allow efficient uptake and presentation of gluten peptides to gluten-specific T cells.


Enhanced B-Cell Receptor Recognition of the Autoantigen Transglutaminase 2 by Efficient Catalytic Self-Multimerization.

Stamnaes J, Iversen R, du Pré MF, Chen X, Sollid LM - PLoS ONE (2015)

Presentation of gluten peptide by TG2-specific B cells upon incubation with TG2-gluten peptide complexesA20 B cells expressing HLA-DQ2.5 alone or in combination with TG2-specific (679-14-E06) or non TG2-specific (693-2-F02) IgD BCR were incubated with size-fractionated complexes of TG2 and FITC-33mer peptide, and their ability to present deamidated peptide to DQ2.5-glia-α2-specific hybridoma T cells was assessed by measuring release of IL-2. When incubated with the free, deamidated peptide (33merE), all A20 cells were capable of presenting peptide to the T cells. Only TG2-specific cells, however, could take up and present complexes of TG2 and peptide.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4526674&req=5

pone.0134922.g006: Presentation of gluten peptide by TG2-specific B cells upon incubation with TG2-gluten peptide complexesA20 B cells expressing HLA-DQ2.5 alone or in combination with TG2-specific (679-14-E06) or non TG2-specific (693-2-F02) IgD BCR were incubated with size-fractionated complexes of TG2 and FITC-33mer peptide, and their ability to present deamidated peptide to DQ2.5-glia-α2-specific hybridoma T cells was assessed by measuring release of IL-2. When incubated with the free, deamidated peptide (33merE), all A20 cells were capable of presenting peptide to the T cells. Only TG2-specific cells, however, could take up and present complexes of TG2 and peptide.
Mentions: Help from gluten-reactive T cells following B-cell uptake of TG2-gluten complexes is likely crucial for the development of the anti-TG2 response in celiac disease. As valency of TG2 had a clear impact on B-cell activation, we next addressed if this also is reflected in increased activation of gluten-specific T cells. Size-fractionated TG2 cross-linked in the presence of FITC labeled 33mer gluten peptide, which harbors multiple copies of the DQ2.5-glia-α2 epitope, was offered to the transduced A20 lymphoma cells and T-cell activation was assessed by IL-2 production of a T-cell hybridoma expressing T-cell receptor specific for the HLA-DQ2.5-glia-α2 epitope. When offering equal amounts of antigen (in μg TG2), TG2-33mer dimer and multimer were more effective at inducing IL-2 production than TG2-33mer monomer (Fig 6). Importantly, T-cell stimulation was dependent on BCR internalization as no T-cell proliferation was observed using TG2 multimers with non TG2-specific cells. Self-crosslinked TG2 multimers harboring gluten T-cell epitopes are thus highly potent B-cell activators that also allow efficient uptake and presentation of gluten peptides to gluten-specific T cells.

Bottom Line: The presence of exogenous substrate such as gluten peptide does not inhibit TG2 self-cross-linking, but rather results in formation of TG2-TG2-gluten complexes.TG2 multimers are superior to TG2 monomer in activating A20 B cells transduced with TG2-specific B-cell receptor, and uptake of TG2-TG2-gluten multimers leads to efficient activation of gluten-specific T cells.Importantly, high avidity of the antigen could explain why TG2-specific plasma cells show signs of an extrafollicular generation pathway.

View Article: PubMed Central - PubMed

Affiliation: Centre for Immune Regulation and Department of Immunology, University of Oslo and Oslo University Hospital, Oslo, Norway.

ABSTRACT
A hallmark of the gluten-driven enteropathy celiac disease is autoantibody production towards the enzyme transglutaminase 2 (TG2) that catalyzes the formation of covalent protein-protein cross-links. Activation of TG2-specific B cells likely involves gluten-specific CD4 T cells as production of the antibodies is dependent on disease-associated HLA-DQ allotypes and dietary intake of gluten. IgA plasma cells producing TG2 antibodies with few mutations are abundant in the celiac gut lesion. These plasma cells and serum antibodies to TG2 drop rapidly after initiation of a gluten-free diet, suggestive of extrafollicular responses or germinal center reactions of short duration. High antigen avidity is known to promote such responses, and is also important for breakage of self-tolerance. We here inquired whether TG2 avidity could be a feature relevant to celiac disease. Using recombinant enzyme we show by dynamic light scattering and gel electrophoresis that TG2 efficiently utilizes itself as a substrate due to conformation-dependent homotypic association, which involves the C-terminal domains of the enzyme. This leads to the formation of covalently linked TG2 multimers. The presence of exogenous substrate such as gluten peptide does not inhibit TG2 self-cross-linking, but rather results in formation of TG2-TG2-gluten complexes. The celiac disease autoantibody epitopes, clustered in the N-terminal part of TG2, are conserved in the TG2-multimers as determined by mass spectrometry and immunoprecipitation analysis. TG2 multimers are superior to TG2 monomer in activating A20 B cells transduced with TG2-specific B-cell receptor, and uptake of TG2-TG2-gluten multimers leads to efficient activation of gluten-specific T cells. Efficient catalytic self-multimerization of TG2 and generation of multivalent TG2 antigen decorated with gluten peptides suggest a mechanism by which self-reactive B cells are activated to give abundant numbers of plasma cells in celiac disease. Importantly, high avidity of the antigen could explain why TG2-specific plasma cells show signs of an extrafollicular generation pathway.

No MeSH data available.


Related in: MedlinePlus