γδ T cell subsets play opposing roles in regulating experimental autoimmune encephalomyelitis
Introduction
MS and its murine model, EAE, are characterized by perivascular T cell and mononuclear cell infiltration in the central nervous system (CNS) with subsequent primary demyelination of axonal tracts leading to progressive paralysis. Autoreactive CD4+ T cells in MS patients and in EAE respond to a variety of myelin membrane constituents including myelin basic protein, myelin proteolipid protein (PLP), and/or myelin-oligodendrocyte glycoprotein, [1], [2] which induce CNS inflammation and demyelination. With the recent revelation that IL-17-mediated inflammation, rather than IFN-γ responses, are most critical during autoimmunity, the research focus has centered on understanding the differentiation and effector functions of CD4+ Th17 cells in EAE and MS [3], [4], [5]. However, conventional Th17 cells are not the sole producers of IL-17. γδ T cells secrete large amounts of IL-17, perhaps even without the clonal expansion or additional TCR stimulation required for the adaptive response [6], [7], [8]. Interestingly, IL-17 producing γδ T cells have been shown to be pathogenic in models of autoimmunity including collagen induced arthritis and protective for airway hyper-reactivity, indicating a pleiotropic role for γδ T cells in immune-mediated pathology [9], [10], [11].
Significant numbers of γδ T cells have been identified in the cerebral spinal fluid and the CNS demyelinating lesions of MS patients. In addition to clonally expanded αβ T cell populations, which use a restricted set of gene segments, γδ T cells also display a restricted repertoire that is over-expressed in MS plaques [12], [13]. Junctional sequence analysis of these expanded cells suggests they are oligoclonal in nature, perhaps indicating specific antigen stimulation. It has been proposed that γδ T cells respond to heat shock proteins, which could be released in response to inflammatory CNS tissue damage [14]. Although the antigen specificity and regulation of these cells is not well understood, it is clear γδ T cells are involved in the autoimmune CNS inflammation in MS.
Past attempts utilizing murine models of MS to study the role of γδ T cells in the pathogenesis of autoimmune demyelination have been contradictory [reviewed in [15]]. On the one hand, γδ T cells have been shown to play a protective role or no role at all during disease. It has been proposed that γδ T cells regulate autoimmune inflammation via Fas–FasL mediated killing of CNS antigen-specific T cells based on the observation that γδ T cell-deficient mice on the B10.PL background develop a chronic disease compared to the monophasic acute disease course seen in the control animals [16], [17]. However, an additional study concluded that regulation of autoreactive inflammation in EAE is specifically the role of T regulatory cells and not γδ T cells [18]. To further complicate the situation γδ T cells have been reported to enhance autoimmunity by restraining Treg responses [19]. Similarly, adoptive transfer of autoreactive CD4+ T cells into γδ-deficient recipient mice on the C57BL/6 (B6) background elicited similar disease as seen in the WT recipient controls suggesting γδ T cells do not play a significant role in the mediation or regulation of effector mechanisms in EAE [20].
Unlike the aforementioned data, other reports support the hypothesis that γδ T cells play a pathogenic role during disease [21], [22], [23]. Targeting γδ T cells with monoclonal antibodies during various stages of disease resulted in the inability to detect the cells as well as decreased disease, suggesting γδ T cells play a critical role in the pathogenesis of EAE during both acute and chronic phases [24]. Similarly, in both actively induced and adoptively transferred EAE in B6 mice that genetically lack γδ T cells, EAE disease was significantly reduced [25]. These diverse and conflicting results obtained from animal model studies aimed to dissect the mechanisms of γδ T cell involvement in demyelinating disease could attributed to the use of a variety of mouse strains, inducing antigens and methods of γδ T cell manipulation, namely genetic depletions or monoclonal antibody targeting in vivo.
γδ T cells are a heterogeneous population and perhaps the pleiotropic nature of this cell subset and thus the variety of results from many different studies aimed at determining their role during EAE and MS may be explained by a dichotomy of γδ T cell subset function. We therefore sought to examine a possible dichotomy of these pleiotropic cells within the murine model of MS with the goal of clarifying the previous controversy surrounding the role of γδ T cells in EAE as well as to provide evidence for an alternative method of specifically targeting these cells as a possible treatment for MS. Our study indicates that γδ T cell subsets play opposing roles, such that targeted treatment could optimize the regulation of disease. We show that Vγ4-expressing γδ T cells constitute a significant proportion of IL-17-producing cells in the CNS during EAE pathogenesis and when activated in vivo, exacerbate disease symptoms due to their pathogenic nature. Conversely, the Vγ1 subset plays a protective role and perhaps eliciting function at the priming stage within the spleen rather than in the CNS. Using a γδ T cell reporter mouse we were able to show that in vivo antibody treatment resulted in activation of the γδ T cell subsets and not depletion. Collectively, these data provide some much needed explanation for the contradictory literature surrounding the role of γδ T cells during EAE. We propose that γδ T cell subsets show distinct and opposing functions, such that antibody targeting of these cells may allow a more carefully defined inhibition of the pathogenic response in MS, while maintaining the protective immune mechanisms of these critical immune cells.
Section snippets
Mice and peptides
Female SJL/J (Harlan Sprague Dawley), C57BL/6J and Tcrd−/− (The Jackson Laboratory) and Tcrd-eGFP mice [26] were housed under specific pathogen-free conditions in the Northwestern University Animal Facility. All protocols were approved by Northwestern University Animal Care and Use Committee. PLP139–151 (HSLGKWLGHPDKF) and MOG35–55 (MEVGWYRSPFSRVVHLYRNGK), were purchased from Genemed Synthesis (San Francisco, CA).
Induction of EAE
Chronic EAE (C-EAE) was induced in Tcrd-eGFP, Tcrd−/−, and C57BL/6 mice with 200 μg
γδ T cell subsets accumulate in the CNS of SJL/J mice with PLP139–151-induced EAE correlates with relapsing-remitting disease severity and co-localize with CD4+ T cells
Interestingly, a limited repertoire of γδ T cells, defined by TCR chain usage, have been seen in the CSF and lesions of MS patients, however their function is not understood. The relapsing-remitting EAE model (R-EAE) closely represents the most common form of MS, characterized by repeating bouts of paralytic symptoms interrupted by remissions. Previous studies have examined the role of γδ T cells using multiple EAE models of MS, however the results are conflicting in that these cells have been
Discussion
γδ T cells have been identified in both lesions and the CSF of MS patients and display a limited repertoire, however their function is unknown. Past literature using the EAE model of MS is filled with contradictory data as to whether these cells play a pathogenic or protective role [15]. As a population, γδ T cells display a broad functional spectrum that may segregate into the multiple subsets defined by the TCR variable region. In this study we characterize the two main circulating subsets of
Acknowledgments
This work was supported by Grants from the Myelin Repair Foundation and NIH Grant NS-026543. We thank Dr. Liang Zhou for his assistance with real time PCR primers and for helpful discussions. We also thank Dr. William Karpus for the generous gift of PCR primers for chemokines. The authors declare no competing financial interests.
References (66)
- et al.
Multi-peptide coupled-cell tolerance ameliorates ongoing relapsing EAE associated with multiple pathogenic autoreactivities
J. Autoimmun.
(2006) - et al.
Interleukin-17-producing gammadelta T cells selectively expand in response to pathogen products and environmental signals
Immunity
(2009) - et al.
Interleukin-1 and IL-23 induce innate IL-17 production from gammadelta T cells, amplifying Th17 responses and autoimmunity
Immunity
(2009) - et al.
Phagocytosis of apoptotic neutrophils regulates granulopoiesis via IL-23 and IL-17
Immunity
(2005) - et al.
Gamma delta T cells enhance autoimmunity by restraining regulatory T cell responses via an interleukin-23-dependent mechanism
Immunity
(2010) - et al.
Adoptively transferred EAE in gamma delta T cell-knockout mice
J. Autoimmun.
(1998) - et al.
Stimulation of a major subset of lymphocytes expressing T cell receptor gamma delta by an antigen derived from Mycobacterium tuberculosis
Cell
(1989) - et al.
Aggravation of murine experimental allergic encephalomyelitis by administration of T-cell receptor gammadelta-specific antibody
J. Neuroimmunol.
(1997) - et al.
Distinct gene expression in human Vdelta1 and Vdelta2 gammadelta T cells following non-TCR agonist stimulation
Mol. Immunol.
(2006) - et al.
Interleukin-17 production in central nervous system-infiltrating T cells and glial cells is associated with active disease in multiple sclerosis
Am. J. Pathol.
(2008)
Plasticity of CD4+ T cell lineage differentiation
Immunity
The aryl hydrocarbon receptor in immunity
Trends Immunol.
Wrapping it up: the cell biology of myelination
Curr. Opin. Neurobiol.
Gamma delta T cell receptor repertoire in brain lesions of patients with multiple sclerosis
J. Neuroimmunol.
New targets for treatment of multiple sclerosis
J. Neurol. Sci.
Multiple sclerosis: deeper understanding of its pathogenesis reveals new targets for therapy
Annu. Rev. Neurosci.
Mice with a disrupted IFN-gamma gene are susceptible to the induction of experimental autoimmune encephalomyelitis (EAE)
J. Immunol.
A distinct lineage of CD4 T cells regulates tissue inflammation by producing interleukin 17
Nat. Immunol.
Interleukin 17-producing CD4+ effector T cells develop via a lineage distinct from the T helper type 1 and 2 lineages
Nat. Immunol.
Exacerbation of collagen-induced arthritis by oligoclonal, IL-17-producing gamma delta T cells
J. Immunol.
Resolution of allergic airway inflammation and airway hyperreactivity is mediated by IL-17 Producing gamma-delta T Cells
Am. J. Respir. Crit. Care Med.
Pivotal role of cerebral interleukin-17-producing gammadelta T cells in the delayed phase of ischemic brain injury
Nat. Med.
Gamma delta T-cell receptor repertoire in acute multiple sclerosis lesions
Proc. Natl. Acad. Sci. U.S.A.
The immunopathology of acute experimental allergic encephalomyelitis induced with myelin proteolipid protein. T cell receptors in inflammatory lesions
J. Immunol.
Human gamma delta+ T cells respond to mycobacterial heat-shock protein
Nature
The contribution of gammadelta T cells to the pathogenesis of EAE and MS
Curr. Mol. Med.
Gamma delta T cell regulation of IFN-gamma production by central nervous system-infiltrating encephalitogenic T cells: correlation with recovery from experimental autoimmune encephalomyelitis
J. Immunol.
Gamma delta T cells regulate the extent and duration of inflammation in the central nervous system by a Fas ligand-dependent mechanism
J. Immunol.
Regulatory CD4(+) T cells expressing endogenous T cell receptor chains protect myelin basic protein-specific transgenic mice from spontaneous autoimmune encephalomyelitis
J. Exp. Med.
The effect of gammadelta T cell depletion on cytokine gene expression in experimental allergic encephalomyelitis
J. Immunol.
Gammadelta T cells enhance the expression of experimental autoimmune encephalomyelitis by promoting antigen presentation and IL-12 production
J. Immunol.
Gamma/delta T cell-deficient mice exhibit reduced disease severity and decreased inflammatory response in the brain in murine neurocysticercosis
J. Immunol.
A pathogenic role for gamma delta T cells in relapsing-remitting experimental allergic encephalomyelitis in the SJL mouse
J. Immunol.
Cited by (58)
The immune system in neurological diseases: What innate-like T cells have to say
2024, Journal of Allergy and Clinical ImmunologyNeuro-immune crosstalk in depressive symptoms of multiple sclerosis
2023, Neurobiology of DiseaseREV-ERB agonist suppresses IL-17 production in γδT cells and improves psoriatic dermatitis in a mouse model
2021, Biomedicine and Pharmacotherapyγδ T lymphocytes in the pathogenesis of multiple sclerosis and experimental autoimmune encephalomyelitis
2019, Journal of NeuroimmunologyCitation Excerpt :Moreover, IL-23-activated γδ T lymphocytes inhibit the conversion of naive αβ T cells into Foxp3+ Tregs in a yet unknown mechanism as well as revoke a Treg-mediated supression of effector T cells (Petermann et al., 2010). Apart from the already mentioned cytokines, CCL3, CCL4 and CCL5 are also secreted by γδ T lymphocytes during EAE with significantly higher amounts produced by Vγ1 than Vγ4 (Blink et al., 2014). A small subset of γδ T cells is also capable of secreting IL-15, thus is termed γδ T15 (Wang et al., 2015).