Does citrullination occur in medullary thymic epithelial cells?
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1
University Medicine Rostock, Institute of Immunology, Germany
Introduction
The presence of antibodies against citrullinated peptide antigens (ACPA) is a hallmark of rheumatoid arthritis. However, it is unclear how these autoantibodies develop. It has been proposed, that peripheral citrullination generates neoepitopes that are favored targets of autoreactive immune cells evading central tolerance induction. We investigated the expression of peptidyl arginine deiminases (PAD) in medullary thymic epithelial cells (mTEC).
Methods
Thymic epithelial cells were isolated from 4-5 weeks old mice susceptible (DBA/1) or not susceptible (NMRI, C57BL/6) for collagen-induced arthritis (CIA). After TEC-enrichment by percoll density gradient centrifugation and magnetic depletion of CD45+ cells, immature mTEC (CD45-EpCAM+CD80lowLy-51-) and mature mTEC (CD45-EpCAM+CD80highLy-51-) were FACS-sorted. Cortical TEC were identified as CD45-EpCAM+CD80-Ly-51+. mRNA and protein were isolated from sorted mTEC populations for
subsequent expression analysis.
Results
Flow cytometry analysis revealed a significantly decreased number of mTEC in thymi of CIA-susceptible DBA/1 mice in comparison to NMRI and C57BL/6 mice, whereas the number of T cells and cTEC did not show any differences. Subsequent quantitative PCR confirmed cell identity since mature mTEC showed significantly elevated expression of aire and the tissue restricted gene insulin2 compared to immature ones. Pad expression was higher in mature mTEC compared to immature mTEC and correlated well with the expression of aire. Furthermore, the expression of pad6 was significantly elevated in DBA/1 mature mTEC.
Conclusion
Pad genes are readily expressed at RNA level in murine mTEC. However, it remains to be determined whether PAD protein and citrullination can also be found in mTEC. This is work in progress.
Keywords:
citrullination,
neoepitopes,
collagen-induced arthritis,
Central Tolerance,
Thymus Gland
Conference:
15th International Congress of Immunology (ICI), Milan, Italy, 22 Aug - 27 Aug, 2013.
Presentation Type:
Abstract
Topic:
Immune-mediated disease pathogenesis
Citation:
Engelmann
R,
Biemelt
A,
Johl
A and
Müller-Hilke
B
(2013). Does citrullination occur in medullary thymic epithelial cells?.
Front. Immunol.
Conference Abstract:
15th International Congress of Immunology (ICI).
doi: 10.3389/conf.fimmu.2013.02.00674
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Received:
12 Jun 2013;
Published Online:
22 Aug 2013.
*
Correspondence:
Dr. Robby Engelmann, University Medicine Rostock, Institute of Immunology, Rostock, Germany, robby.engelmann@med.uni-rostock.de