Research Papers: Immunology:
Ectonucleotidase activity and immunosuppression in astrocyte-CD4 T cell bidirectional signaling
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Fabia Filipello1, Davide Pozzi1,*, Michele Proietti2,6,*, Andrea Romagnani2,3, Sonia Mazzitelli1,7, Michela Matteoli1,4,**, Claudia Verderio1,4,** and Fabio Grassi2,5,**
1 Laboratory of Pharmacology and Brain Pathology, Humanitas Clinical and Research Center, Rozzano, Italy
2 Institute for Research in Biomedicine, Bellinzona, Switzerland
3 Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
4 CNR Institute of Neuroscience, Milano, Italy
5 Department of Medical Biotechnology and Translational Medicine, University of Milan, Istituto Nazionale di Genetica Molecolare, Milan, Italy
6 Center of Chronic Immunodeficiency, University Medical Center, Freiburg, Germany
7 Hertie Institute for Clinical Brain Research, University of Tubingen, Department of Cellular Neurology, Tubingen, Germany
* These authors have contributed equally to this work
** Co-senior author
Fabio Grassi, email:
Keywords: astrocyte, ectonucleotidase, calcium, immunosuppression, T cell, Immunology and Microbiology Section, Immune response, Immunity
Received: August 06, 2015 Accepted: January 01, 2016 Published: January 13, 2016
Astrocytes play a crucial role in neuroinflammation as part of the glia limitans, which regulates infiltration of the brain parenchyma by leukocytes. The signaling pathways and molecular events, which result from the interaction of activated T cells with astrocytes are poorly defined. Here we show that astrocytes promote the expression and enzymatic activity of CD39 and CD73 ectonucleotidases in recently activated CD4 cells by a contact dependent mechanism that is independent of T cell receptor interaction with class II major histocompatibility complex (MHC). Transforming growth factor-β (TGF-β) is robustly upregulated and sufficient to promote ectonucleotidases expression. T cell adhesion to astrocyte results in differentiation to an immunosuppressive phenotype defined by expression of the transcription factor Rorγt, which characterizes the CD4 T helper 17 subset. CD39 activity in T cells in turn inhibits spontaneous calcium oscillations in astrocytes that correlated with enhanced and reduced transcription of CCL2 chemokine and Sonic hedgehog (Shh), respectively. We hypothesize this TCR-independent interaction promote an immunosuppressive program in T cells to control possible brain injury by deregulated T cell activation during neuroinflammation. On the other hand, the increased secretion of CCL2 with concomitant reduction of Shh might promote leukocytes extravasation into the brain parenchyma.
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