The majority of intestinal IgA+ and IgG+ plasmablasts in the human gut are antigen-specific
Julia Benckert, … , Bertram Wiedenmann, Hedda Wardemann
Julia Benckert, … , Bertram Wiedenmann, Hedda Wardemann
Published April 1, 2011
Citation Information: J Clin Invest. 2011;121(5):1946-1955. https://doi.org/10.1172/JCI44447.
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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 4

Reactivity of IgA and IgG lamina propria plasmablast antibodies with intestinal microbes.

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Reactivity of IgA and IgG lamina propria plasmablast antibodies with int...
IgA and IgG plasma cell antibodies from HD1–HD3 were tested for reactivity with a panel of nonpathogenic and enteropathogenic intestinal microbes. The data shown are representative for at least 2 independent experiments. (A) ELISA graphs show the reactivity profile (black line) of a representative bacteria-polyreactive antibody (HD2g348) with E. coli, M. morganii, E. cloacae, and E. faecalis. High positive (dashed line, ED38; ref. 40), low positive (red line, JB40; ref. 23), and nonreactive (green line, mGO53; ref. 23) antibodies were included in each assay for comparison. Horizontal lines indicate the cutoff OD405 in each assay. (B) Bar graphs summarize the frequency of bacteria polyreactive antibodies (black) and non-bacteria polyreactive IgA and IgG antibodies (white) in each donor as determined by ELISA as in A. (C) Representative ELISA graphs show the reactivity of E. coli, M. morganii, E. cloacae, and rotavirus-specific IgA and IgG plasma cell antibodies from HD1–HD3. Clone names of bacteria-specific antibodies are indicated in the graphs. Additional high positive (dashed line, ED38; ref. 40), low positive (red line, JB40; ref. 23) and nonreactive (green line, mGO53; ref. 23) control antibodies were included in each assay for comparison. Horizontal lines indicate the cutoff OD405 in each assay. (D) Histograms show binding of E. coli–specific (HD3g76, HD3g144) and M. morganii–specific (HD3g71) antibodies to whole bacteria as measured by FACS. Secondary antibody only (neg. control) was included as control in all assays.