The majority of intestinal IgA+ and IgG+ plasmablasts in the human gut are antigen-specific
Julia Benckert, Nina Schmolka, Cornelia Kreschel, Markus Josef Zoller, Andreas Sturm, Bertram Wiedenmann, Hedda Wardemann
Julia Benckert, Nina Schmolka, Cornelia Kreschel, Markus Josef Zoller, Andreas Sturm, Bertram Wiedenmann, Hedda Wardemann
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Research Article Immunology

The majority of intestinal IgA+ and IgG+ plasmablasts in the human gut are antigen-specific

Abstract

Mucosal antibody responses play a major role in mediating homeostasis with the intestinal flora. It has been suggested that imbalance in the IgA+ and IgG+ intestinal B cell repertoire may be associated with the development of diseases such as inflammatory bowel disease. Despite this, little is known about the antibody specificity of human intestinal plasmablasts. Here, we have determined the reactivity profile of single isolated IgA+ and IgG+ plasmablasts from human terminal ileum using antibody cloning and in vitro expression. We found that approximately 25% of intestinal IgA and IgG plasmablast antibodies were polyreactive; the majority were antigen-specific. Antigen specificity was not only directed against enteropathogenic microbes but also against commensal microbes and self antigens. Regardless of their reactivity, all intestinal antibodies were somatically mutated and showed signs of antigen-mediated selection, suggesting that they developed from antigen-specific B cell responses. Together, our data indicate that antigen-specific immune responses to intestinal microbes are largely responsible for the maintenance of intestinal homeostasis and thus provide a basis for understanding the deregulated immune responses observed in patients with inflammatory bowel disease.

Authors

Julia Benckert, Nina Schmolka, Cornelia Kreschel, Markus Josef Zoller, Andreas Sturm, Bertram Wiedenmann, Hedda Wardemann

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Figure 3

Self-reactivity of IgA and IgG lamina propria plasmablasts.

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Self-reactivity of IgA and IgG lamina propria plasmablasts. IgA and IgG ...
IgA and IgG plasma cell antibodies from HD1–HD3 were tested for self-reactivity (A–C) by IFA with HEp-2 cells and (D–F) on intestinal tissue sections. (A) Representative cytoplasmic, cytoplasmic and nuclear, and nuclear HEp-2 cell staining patterns. A non-HEp-2 cell–reactive antibody is shown for comparison. Scale bars: 20 μm. (B) Pie charts summarize the frequency of non-HEp-2 cell–reactive (white) and HEp-2 cell–reactive antibodies, with cytoplasmic (light gray), cytoplasmic and nuclear (dark gray), and nuclear (black) reactivity. The number of tested antibodies is indicated in the pie chart center. Other numbers in each section represent the frequency of antibodies for each condition, respectively. (C) Bar graphs summarize the frequency of antinuclear (black), anticytoplasmic and antinuclear (dark gray), anticytoplasmic (light gray), and non-self-reactive (white) antibodies for HD1–HD3. Hatched areas indicate polyreactive antibodies. Standard deviation of means is indicated. (D) Representative specific and polyreactive intestinal tissue staining patterns (purple). Hoechst-stained nuclei are shown in green. Scale bars: 50 μm. (E) Pie charts show the frequency of non-intestinal tissue–reactive antibodies (white) and intestinal tissue–reactive antibodies (black) for each HD. The number of tested antibodies is indicated in the pie chart center. Other numbers in each section represent the frequency of antibodies for each condition, respectively. (F) Bar graphs summarize the frequency of tissue reactive (black) and non-tissue reactive (white) IgA and IgG antibodies, respectively, for HD1–HD3. Hatched areas indicate polyreactive antibodies. Standard deviation of means is indicated.