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IgG-mediated suppression of IgG responses to erythrocytes is epitope specific
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology. (Birgitta Heyman)
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology. (Birgitta Heyman)
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology. (Birgitta Heyman)
(English)Manuscript (preprint) (Other academic)
Keyword [en]
IgG-mediated suppression, antibody, B cell
National Category
Immunology
Research subject
Immunology
Identifiers
URN: urn:nbn:se:uu:diva-302596OAI: oai:DiVA.org:uu-302596DiVA: diva2:958381
Available from: 2016-09-07 Created: 2016-09-07 Last updated: 2016-09-09
In thesis
1. Modulation of B cell access to antigen by passively administered antibodies: an explanation for antibody feedback regulation?
Open this publication in new window or tab >>Modulation of B cell access to antigen by passively administered antibodies: an explanation for antibody feedback regulation?
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Antibody responses can be up- or down-regulated by passive administration of specific antibody together with antigen. Depending on the structure of the antigen and the antibody isotype, responses can be completely suppressed or enhanced up to a 1000-fold of what is seen in animals immunized with antigen alone.

IgG suppresses primary antibody responses against erythrocytes. Suppression works well in mice lacking Fc-receptors for IgG, C1q, C3, or complement receptor 1 and 2 (CR1/2). Here, we demonstrate that IgG anti-NP given to mice together with NP-conjugated sheep erythrocytes, suppresses the generation of NP-specific extra-follicular antibody-secreting cells, NP-specific germinal center B cells, induction of memory and long-lived plasma cells. IgG increases antigen clearance but this does not explain the suppressed antibody response. It is demonstrated that IgG-mediated suppression of IgG responses is epitope specific, suggesting that epitope masking is the dominant explanation for IgG-mediated suppression of antibody responses.

Both IgE and IgG3 can enhance antibody responses against soluble antigens. IgE-antigen complexes bind to recirculating B cells expressing CD23, an Fc-receptor for IgE.  Thirty minutes after intravenous administration, IgE-antigen is found in splenic follicles. Subsequently, germinal center responses, antigen-specific T cell proliferation, and antibody responses are enhanced. We show that also antigen conjugated to anti-CD23 can bind to CD23+ B cells and be transported to splenic follicles. CD11+ spleen cells, rather than CD23+ B cells, present IgE-antigen complexes to T cells. Here, it is demonstrated that CD8α conventional dendritic cells is the CD11c+ cell population presenting IgE-antigen to T cells.

IgG3-mediated enhancement is dependent on CR1/2. We find that IgG3-antigen complexes, administered intravenously to mice, bind to marginal zone B cells via CR1/2. These cells then transport IgG3-antigen into splenic follicles and deposit antigen onto follicular dendritic cells. Mice treated with FTY720, a drug which dislocates marginal zone B cells from the marginal zone, impairs this transport. Studies in bone marrow chimeric mice show that CR1/2 on both B cells and follicular dendritic cells are crucial for IgG3-mediated enhancement.

In summary, these observations suggest that antibodies can feedback regulate antibody responses by modulating the access of antigen to the immune system. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 57 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1255
Keyword
IgG, IgG3, IgE, suppression, enhancement, epitope masking, antigen transport, antigen presentation, follicular B cells, marginal zone B cells
National Category
Immunology Immunology in the medical area
Research subject
Immunology
Identifiers
urn:nbn:se:uu:diva-302780 (URN)978-91-554-9697-5 (ISBN)
Public defence
2016-12-01, C8:301, BMC, Husargatan 3, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2016-11-09 Created: 2016-09-09 Last updated: 2016-11-16

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