ICAM1+ neutrophils promote chronic inflammation via ASPRV1 in B cell–dependent autoimmune encephalomyelitis
Ryder F. Whittaker Hawkins, … , Martin Pelletier, Luc Vallières
Ryder F. Whittaker Hawkins, … , Martin Pelletier, Luc Vallières
Published December 7, 2017
Citation Information: JCI Insight. 2017;2(23):e96882. https://doi.org/10.1172/jci.insight.96882.
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Research Article Neuroscience

ICAM1+ neutrophils promote chronic inflammation via ASPRV1 in B cell–dependent autoimmune encephalomyelitis

Abstract

Neutrophils contribute to demyelinating autoimmune diseases, yet their phenotype and functions have been elusive to date. Here, we demonstrate that ICAM1 surface expression distinguishes extra- from intravascular neutrophils in the mouse CNS during experimental autoimmune encephalomyelitis (EAE). Transcriptomic analysis of these 2 subpopulations indicated that neutrophils, once extravasated, acquire macrophage-like properties, including the potential for immunostimulation and MHC class II–mediated antigen presentation. In corroboration, super-resolution (3D stimulated emission-depletion [STED]) microscopy revealed neutrophils forming synapses with T and B cells in situ. Further, neutrophils specifically express the aspartic retroviral-like protease ASPRV1, which increases in the CNS during EAE and severe cases of multiple sclerosis. Without ASPRV1, mice immunized with a new B cell–dependent myelin antigen (but not with the traditional myelin oligodendrocyte glycoprotein peptide) develop a chronic phase of EAE that is less severe and even completely fades in many individuals. Therefore, ICAM1+ macrophage–like neutrophils can play both shared and nonredundant roles in autoimmune demyelination, among them perpetuating inflammation via ASPRV1.

Authors

Ryder F. Whittaker Hawkins, Alexandre Patenaude, Aline Dumas, Rajiv Jain, Yodit Tesfagiorgis, Steven Kerfoot, Takeshi Matsui, Matthias Gunzer, Patrice E. Poubelle, Catherine Larochelle, Martin Pelletier, Luc Vallières

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Figure 1

The spinal cord of EAE mice contains 2 subsets of neutrophils distinguishable by ICAM1 surface expression.

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The spinal cord of EAE mice contains 2 subsets of neutrophils distinguis...
(A) Flow cytometry gating strategy used to analyze neutrophils (CD45+CD11b+Ly6G+CD19–CD3ε–) from the spinal cord or blood of mice euthanized 15 days after immunization either with or without MOG35–55 (EAE or sham, respectively). Naive mice were used as additional controls. Dead cells and doublets were excluded. (B) Quantification of the data in A revealing an increase of neutrophils in the spinal cord and blood of EAE and sham-treated mice. For the spinal cords, counts were normalized to CD45– cells as an internal control. Stars indicate significant increases from both the naive and sham-treated mice (closed star) or from the naive mice only (open star), as determined by 2-way ANOVA and post hoc 2-tailed Student’s t test (P ≤ 0.0089). Sample size for spinal cord: 21 (EAE), 10 (sham, naive). Sample size for blood: 13 (EAE), 7 (sham), 6 (naive). (C) Cytometric analysis of ICAM1 on neutrophils from the spinal cord or blood of EAE and control mice. Data were gated as in A. (D) Quantification of the data in C revealing a strong increase of ICAM1 expression on neutrophils isolated from the spinal cord of EAE mice. Left charts, counts of ICAM1+ and ICAM1– neutrophils in the spinal cord and blood. Right charts, median fluorescence intensity (MFI) obtained for ICAM1 when gated on the whole population of neutrophils or only on those positive for ICAM1. Stars indicate significant increases of ICAM1+ neutrophils from both the naive and sham-treated mice (closed star) or from the naive mice only (open star), as determined by 2-way ANOVA and post hoc 2-tailed Student’s t test (P ≤ 0.0016). Sample size as in B.