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Budzyńska PM, Kyläniemi MK, Lassila O, Nera KP, Alinikula J. BLIMP-1 is insufficient to induce antibody secretion in the absence of IRF4 in DT40 cells. Scand J Immunol 2018; 87. [PMID: 29430664 DOI: 10.1111/sji.12646] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Accepted: 02/01/2018] [Indexed: 01/18/2023]
Abstract
Differentiation of B cells into antibody-secreting cells (ASCs), plasmablasts and plasma cells is regulated by a network of transcription factors. Within this network, factors including PAX5 and BCL6 prevent ASC differentiation and maintain the B cell phenotype. In contrast, BLIMP-1 and high IRF4 expression promote plasma cell differentiation. BLIMP-1 is thought to induce immunoglobulin secretion, whereas IRF4 is needed for the survival of ASCs. The role of IRF4 in the regulation of antibody secretion has remained controversial. To study the role of IRF4 in the regulation of antibody secretion, we have created a double knockout (DKO) DT40 B cell line deficient in both IRF4 and BCL6. Although BCL6-deficient DT40 B cell line had upregulated BLIMP-1 expression and secreted antibodies, the DKO cell line did not. Even enforced BLIMP-1 expression in DKO cells or IRF4-deficient cells could not induce IgM secretion while in WT DT40 cells, it could. However, enforced IRF4 expression in DKO cells induced strong IgM secretion. Our findings support a model where IRF4 expression in addition to BLIMP-1 expression is required to induce robust antibody secretion.
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Affiliation(s)
- P M Budzyńska
- Department of Medical Microbiology and Immunology, Institute of Biomedicine, University of Turku, Turku, Finland.,Turku Doctoral Programme of Biomedical Sciences and Turku Doctoral Programme of Molecular Medicine, University of Turku, Turku, Finland
| | - M K Kyläniemi
- Department of Medical Microbiology and Immunology, Institute of Biomedicine, University of Turku, Turku, Finland
| | - O Lassila
- Department of Medical Microbiology and Immunology, Institute of Biomedicine, University of Turku, Turku, Finland.,Department of Clinical Microbiology and Immunology, Turku University Hospital, Turku, Finland
| | - K-P Nera
- Department of Medical Microbiology and Immunology, Institute of Biomedicine, University of Turku, Turku, Finland
| | - J Alinikula
- Department of Medical Microbiology and Immunology, Institute of Biomedicine, University of Turku, Turku, Finland
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Budzyńska PM, Niemelä M, Sarapulov AV, Kyläniemi MK, Nera KP, Junttila S, Laiho A, Mattila PK, Alinikula J, Lassila O. IRF4 Deficiency Leads to Altered BCR Signalling Revealed by Enhanced PI3K Pathway, Decreased SHIP Expression and Defected Cytoskeletal Responses. Scand J Immunol 2016; 82:418-28. [PMID: 26173778 DOI: 10.1111/sji.12343] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 07/07/2015] [Indexed: 12/13/2022]
Abstract
The graded expression of transcription factor interferon regulatory factor 4 (IRF4) regulates B cell development and is critical for plasma cell differentiation. However, the mechanisms, by which IRF4 elicits its crucial tasks, are largely unknown. To characterize the molecular targets of IRF4 in B cells, we established an IRF4-deficient DT40 B cell line. We found that in the absence of IRF4, the expression of several molecules involved in BCR signalling was altered. For example, the expression of B cell adaptor for PI3K (BCAP) was upregulated, whereas the SHIP (SH2-containing Inositol 5?-Phosphatase) expression was downregulated. These molecular unbalances were accompanied by increased BCR-induced calcium signalling, attenuated B cell linker protein (BLNK) and ERK activity and enhanced activity of PI3K/protein kinase B (Akt) pathway. Further, the IRF4-deficient cells showed dramatically diminished cytoskeletal responses to anti-IgM cross-linking. Our results show that IRF4 has an important role in the regulation of BCR signalling and help to shed light on the molecular mechanisms of B cell development and germinal centre response.
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Affiliation(s)
- P M Budzyńska
- Department of Medical Microbiology and Immunology, University of Turku, Turku, Finland.,Turku Doctoral Programme of Biomedical Sciences, University of Turku, Turku, Finland
| | - M Niemelä
- Department of Medical Microbiology and Immunology, University of Turku, Turku, Finland
| | - A V Sarapulov
- Institute of Biomedicine, Department of Pathology, University of Turku, Turku, Finland
| | - M K Kyläniemi
- Department of Medical Microbiology and Immunology, University of Turku, Turku, Finland
| | - K-P Nera
- Department of Medical Microbiology and Immunology, University of Turku, Turku, Finland
| | - S Junttila
- The Finnish Microarray and Sequencing Center, Turku Centre for Biotechnology, Turku, Finland
| | - A Laiho
- The Finnish Microarray and Sequencing Center, Turku Centre for Biotechnology, Turku, Finland
| | - P K Mattila
- Institute of Biomedicine, Department of Pathology, University of Turku, Turku, Finland
| | - J Alinikula
- Department of Medical Microbiology and Immunology, University of Turku, Turku, Finland
| | - O Lassila
- Department of Medical Microbiology and Immunology, University of Turku, Turku, Finland
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