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IgG Suppresses Antibody Responses in Mice Lacking C1q, C3, Complement Receptors 1 and 2, or IgG Fc-Receptors.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
2015 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, no 11Article in journal (Refereed) Published
Abstract [en]

Antigen-specific IgG antibodies, passively administered to mice or humans together with large particulate antigens like erythrocytes, can completely suppress the antibody response against the antigen. This is used clinically in Rhesus prophylaxis, where administration of IgG anti-RhD prevents RhD-negative women from becoming immunized against RhD-positive fetal erythrocytes aquired transplacentally. The mechanisms by which IgG suppresses antibody responses are poorly understood. We have here addressed whether complement or Fc-receptors for IgG (FcγRs) are required for IgG-mediated suppression. IgG, specific for sheep red blood cells (SRBC), was administered to mice together with SRBC and the antibody responses analyzed. IgG was able to suppress early IgM- as well as longterm IgG-responses in wildtype mice equally well as in mice lacking FcγRIIB (FcγRIIB knockout mice) or FcγRI, III, and IV (FcRγ knockout mice). Moreover, IgG was able to suppress early IgM responses equally well in mice lacking C1q (C1qA knockout mice), C3 (C3 knockout mice), or complement receptors 1 and 2 (Cr2 knockout mice) as in wildtype mice. Owing to the previously described severely impaired IgG responses in the complement deficient mice, it was difficult to assess whether passively administered IgG further decreased their IgG response. In conclusion, Fc-receptor binding or complement-activation by IgG does not seem to be required for its ability to suppress antibody responses to xenogeneic erythrocytes.

Place, publisher, year, edition, pages
2015. Vol. 10, no 11
National Category
Microbiology in the medical area
Identifiers
URN: urn:nbn:se:uu:diva-270784DOI: 10.1371/journal.pone.0143841ISI: 000365889800078PubMedID: 26619292OAI: oai:DiVA.org:uu-270784DiVA: diva2:890536
Funder
Swedish Research Council, K2012-57X-07492-25-6
Available from: 2016-01-04 Created: 2016-01-04 Last updated: 2017-12-01Bibliographically approved
In thesis
1. A Search for the Masked Mechanism Behind IgG-Mediated Suppression of Antibody Responses
Open this publication in new window or tab >>A Search for the Masked Mechanism Behind IgG-Mediated Suppression of Antibody Responses
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Antibodies passively administered together with their specific antigen can enhance or suppress the specific antibody response. This phenomenon is known as antibody feedback regulation. Whether this modulation causes up- or downregulation of the antibody response depends both on the antibody isotype and the antigen used. IgG antibodies passively administered together with particulate antigens, e.g. erythrocytes, can completely prevent the induction of an antibody response to the antigen. The suppressive capacity of IgG has been routinely used in the clinic since the 1960’s in RhD-prophylaxis to prevent hemolytic disease of the fetus and newborn. Although studied for decades, the underlying mechanism of IgG-suppression has remained elusive. The main focus of this thesis has been to elucidate the mechanism behind IgG-suppression of antibody responses in vivo in mouse models using intravenous immunization with specific IgG together with native or haptenated sheep red blood cells, SRBC. We show that IgG-suppression of IgM and long-term serum IgG-responses operates independently of activating FcγRI, III, IV, or the inhibitory FcγRIIB, thus confirming and extending previous findings. Moreover, we demonstrate for the first time that C1q, C3 and CR1/2 are dispensable for IgG-suppression of antibody responses. These findings strongly argue against the involvement of Fc-dependent mechanisms as the explanation for IgG-suppression. Interestingly, GC formation occurs in IgG-suppressed mice although the antibody response to surface SRBC epitopes are completely suppressed. The data suggests that these GCs develop in response to intracellular SRBC epitopes as well as to the passively administered suppressive IgG. Moreover, we demonstrate that passively administered IgG suppresses several parameters of an antibody/B cell response including antigen specific GC and non-GC B cells, extra-follicular antibody secreting cells, long-lived plasma cells and induction of immunological memory. Before the onset of the present study, two mechanisms appeared compatible with the majority of experimental findings: IgG-mediated antigen clearance and epitope masking. Herein we show that the contribution of IgG-mediated antigen clearance is negligible and that suppression of IgG-responses is strictly epitope specific. This provides compelling evidence that a very important mechanism underlying IgG-suppression is epitope masking.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 67 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1315
Keyword
FcγR, complement, sheep erythrocytes, IgG-mediated immune suppression, rhesus prophylaxis, rhesus D antigen, germinal center
National Category
Immunology in the medical area
Research subject
Immunology
Identifiers
urn:nbn:se:uu:diva-317480 (URN)978-91-554-9853-5 (ISBN)
Public defence
2017-05-11, C8:301, BMC, Husargatan 3, Uppsala, 09:15 (Swedish)
Opponent
Supervisors
Available from: 2017-04-13 Created: 2017-03-16 Last updated: 2017-04-21

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