Activated microglial cells acquire an immature dendritic cell phenotype and may terminate the immune response in an acute model of EAE
Introduction
Antigen presentation is a crucial process in T-cell activation and modulation of immune responses. Two main signals are involved in this process. The first, provided by the engagement of either the MHC-class I or MHC-class II on antigen-presenting cells (APCs) with the T-cell receptor (TCR) on T lymphocytes, controls the specificity of the immune response, as MHC-class I is recognised by CD8+ T cells whereas MHC-class II interacts with CD4+ T cells (Janeway, 1992). The second signal, the co-stimulatory signal, is antigen non-specific, involves the interaction of different T-cell surface receptors with their respective ligands on APCs (Lanzavecchia, 1997, Lenschow et al., 1996) and is essential for the full T-cell activation, as TCR-MHC binding in the absence of co-stimulation can lead to T-cell apoptosis or anergy (Kishimoto and Sprent, 1999). Different combinations of co-stimulatory molecules and receptors providing stimulatory or inhibitory signals have been described (Nurieva et al., 2009), however the signal provided by the B7 molecules, B7.1 and B7.2 on APCs with their receptors CD28 and CTLA-4 in lymphocytes appear to be the predominant molecular interactions for T-cell activation (Salomon and Bluestone, 2001, Sharpe and Freeman, 2002). Binding of B7.1 or B7.2 with CD28 provides a potent stimulatory signal in T cells, whereas binding of the related but higher-affinity CTLA-4 receptor, delivers an inhibitory signal (Karandikar et al., 1996, Sansom, 2000). Therefore, the delicate balance established between these positive and negative signals may provide different outcomes of the immune response.
Evidence for the involvement of antigen presentation in experimental autoimmune encephalomyelitis (EAE) comes from the observations that microglial cells express MHC-class II in different EAE models in both rats (Craggs and Webster, 1985, Matsumoto and Fujiwara, 1986, Matsumoto et al., 1986, McCombe et al., 1994, McCombe et al., 1992) and mice (Juedes and Ruddle, 2001, Lindsey and Steinman, 1993, Ponomarev et al., 2005, Pope et al., 1998), and from studies that reported the expression of co-stimulatory molecules and the beneficial or detrimental effects derived from the lack of these molecules in EAE (Chang et al., 1999, Chang et al., 2003, Girvin et al., 2000, Hurwitz et al., 1997, Karandikar et al., 1998a, Miller et al., 1995, Perrin et al., 1999). It should be emphasised, however, that all the aforementioned studies have been focused only on the peak of the disease and did not address the co-expression of MHCs and B7.1/B7.2-CD28/CTLA-4 molecules in the same context. Thus, it remains to be determined, first, if MHCs expression matches with the presence of these co-stimulatory molecules and if this is the case, whether different combinations of B7.1/B7.2-CD28/CTLA-4 molecules differ during the different phases of EAE and may be playing a role in the initiation and resolution of the immune response. A second question that remains is which are the cells driving the antigen-presenting mechanism within the CNS in this acute EAE model, as in spite of the task of microglia as APCs, some recent studies have reported that a specific population of dendritic cells (DCs), the main APCs in the periphery, infiltrate the CNS in EAE rats (Matyszak and Perry, 1996, Serafini et al., 2000) and MS (Serafini et al., 2006) and play a central role in antigen presentation in murine EAE models (Bailey et al., 2007, Greter et al., 2005), opening the possibility that, in addition to microglia, DCs can be involved in the mechanism of antigen presentation also in this acute model.
Among the different EAE models in rodents, the acute EAE model induced in Lewis rat is of special interest, as it is characterised by a single peak of paralysis after which animals recover spontaneously (Swanborg, 2001, Tsunoda and Fujinami, 1996). Taking advantage of this model, which gave us the opportunity to investigate the mechanisms involved in the induction, peak and resolution of the inflammatory–immune response, the present study provides a detailed description of the temporal expression pattern of MHC/co-stimulatory molecules, and the phenotype of cells responsible for their expression.
Section snippets
EAE induction
A total of 77 female Lewis rats (180–200g) susceptible to develop experimental autoimmune encephalomyelitis (EAE) were used in this study. Animals were purchased from Charles River (IFFA Credo; Belgique) and maintained with food and water ad libitum in a 12 h light/dark cycle.
Rats were induced to develop EAE by a subcutaneous injection, in each hindfoot, of an emulsion containing 100 µg of MBP (M2295; Sigma; St Louis, USA), Complete Freud's Adjuvant (CFA) (Ref. 0638; Difco; USA) and 0.2 mg of
Results
MBP immunisation in Lewis rat produces an acute monophasic disease characterised by a progressive clinical motor impairment, starting around 9–11 days post-immunisation (dpi) reaching complete hindlimb paralysis (12–14 dpi) after which progressive–spontaneous recovery takes place (15–23 dpi). After 23 dpi, clinical symptoms were absent. In this work, in contrast to the major part of studies where experimental groups are determined on the basis of the days post-immunisation, the animals were
Discussion
In this study a detailed analysis of the temporal pattern of expression and cellular distribution of the different molecules (MHCs and co-stimulatory) related to the antigen-presenting mechanism along the different phases of EAE evolution was performed. Firstly, it is important to highlight the fact that no variability was observed in animals analysed in each specific clinical score, indicating that histopathological changes within the CNS are more associated with clinical symptomatology than
Conclusion
In conclusion, our study has shown that in this acute model of EAE, antigen-presenting mechanisms are not restricted to the inductive and peak phases of the disease, but rather they also play an important role during the recovery and post-recovery phases. Our results clearly indicate that during the inductive and the peak phases, antigen presentation to parenchymal CD28+ lymphocytes might take place in the context of MHC molecules without co-stimulatory B7.1/B7.2 signalling, thus may be
Acknowledgements
The authors would to thank Dr Iain L. Campbell for his comments about the manuscript. The authors wish to thank also Miguel A. Martil, Isabella Appiah and Maria González for their outstanding technical help and Mr Chuck Simmons, a native, English speaking Instructor of English in the Autonomous University of Barcelona for the proofreading of this manuscript. The authors also would thank the reviewers for their excellent comments that improve the quality of the manuscript. This work was
References (68)
- et al.
CD4 microglial expression correlates with spontaneous clinical improvement in the acute Lewis rat EAE model
J Neuroimmunol.
(2009) - et al.
Monoclonal antibodies against rat macrophages
J. Immunol. Methods
(1994) - et al.
Estrogen and brain inflammation: effects on microglial expression of MHC, costimulatory molecules and cytokines
J. Neuroimmunol.
(2005) - et al.
T-cell apoptosis in autoimmune diseases: termination of inflammation in the nervous system and other sites with specialized immune-defense mechanisms
Trends Neurosci.
(1997) - et al.
Rapid entry and downregulation of T cells in the central nervous system during the reinduction of experimental autoimmune encephalomyelitis
J. Neuroimmunol.
(2001) - et al.
Specific blockade of CTLA-4/B7 interactions results in exacerbated clinical and histologic disease in an actively-induced model of experimental allergic encephalomyelitis
J. Neuroimmunol.
(1997) - et al.
Microglia-specific localisation of a novel calcium binding protein, Iba1
Brain Res. Mol. Brain Res.
(1998) - et al.
Targeting the B7/CD28:CTLA-4 costimulatory system in CNS autoimmune disease
J. Neuroimmunol.
(1998) - et al.
Ia expression and antigen presentation by glia: strain and cell type-specific differences among rat astrocytes and microglia
J. Neuroimmunol.
(1997) - et al.
Competitive PCR quantification of CD4, CD8, ICAM-1, VCAM-1, and MHC class II mRNA in the central nervous system during development and resolution of experimental allergic encephalomyelitis
J. Neuroimmunol.
(1993)
EAE in beta-2 microglobulin-deficient mice: axonal damage is not dependent on MHC-I restricted immune responses
Neurobiol. Dis.
Mechanisms of axonal degeneration in EAE—lessons from CNTF and MHC I knockout mice
J. Neurol. Sci.
The potential role of dendritic cells in immune-mediated inflammatory diseases in the central nervous system
Neuroscience
Inflammatory cells, microglia and MHC class II antigen-positive cells in the spinal cord of Lewis rats with acute and chronic relapsing experimental autoimmune encephalomyelitis
J. Neuroimmunol.
Expression of CD45RC and Ia antigen in the spinal cord in acute experimental allergic encephalomyelitis: an immunocytochemical and flow cytometric study
J. Neurol. Sci.
Apoptosis of V beta 8.2+ T lymphocytes in the spinal cord during recovery from experimental autoimmune encephalomyelitis induced in Lewis rats by inoculation with myelin basic protein
J. Neurol. Sci.
Blockade of CD28/B7-1 interaction prevents epitope spreading and clinical relapses of murine EAE
Immunity
Minocycline down-regulates MHC II expression in microglia and macrophages through inhibition of IRF-1 and protein kinase C (PKC)alpha/betaII
J. Biol. Chem.
Expression of the actin-bundling protein fascin in cultured human dendritic cells correlates with dendritic morphology and cell differentiation
J. Invest. Dermatol.
Intracerebral recruitment and maturation of dendritic cells in the onset and progression of experimental autoimmune encephalomyelitis
Am. J. Pathol.
Differential modulatory effect of NGF on MHC class I and class II expression in spinal cord cells of EAE rats
J. Neuroimmunol.
Demonstration of poly-N-acetyl lactosamine residues in ameboid and ramified microglial cells in rat brain by tomato lectin binding
J. Histochem. Cytochem.
Fascin is involved in the antigen presentation activity of mature dendritic cells
J. Immunol.
Functional genomic analysis of remyelination reveals importance of inflammation in oligodendrocyte regeneration
J Neurosci.
CNS myeloid DCs presenting endogenous myelin peptides ‘preferentially’ polarize CD4+ T(H)-17 cells in relapsing EAE
Nat. Immunol.
Suppressive properties of human CD4 + CD25+ regulatory T cells are dependent on CTLA-4 expression
Eur. J. Immunol.
CD11c/EYFP transgene illuminates a discrete network of dendritic cells within the embryonic, neonatal, adult, and injured mouse brain
J. Comp. Neurol.
CD1 expression is differentially regulated by microglia, macrophages and T cells in the central nervous system upon inflammation and demyelination
J. Neuroimmunol.
Mature microglia resemble immature antigen-presenting cells
Glia
Ia antigens in the normal rat nervous system and in lesions of experimental allergic encephalomyelitis
Acta Neuropathol.
Studies in B7-deficient mice reveal a critical role for B7 costimulation in both induction and effector phases of experimental autoimmune encephalomyelitis
J. Exp. Med.
Recovery from EAE is associated with decreased survival of encephalitogenic T cells in the CNS of B7-1/B7-2-deficient mice
Eur. J. Immunol.
Antigen-specific inhibition of effector T cell function in humans after injection of immature dendritic cells
J. Exp. Med.
Brain dendritic cells and macrophages/microglia in central nervous system inflammation
J. Immunol.
Cited by (46)
Intranasal delivery of interferon-β-loaded nanoparticles induces control of neuroinflammation in a preclinical model of multiple sclerosis: A promising simple, effective, non-invasive, and low-cost therapy
2021, Journal of Controlled ReleaseCitation Excerpt :Microglia are crucial players of neuroinflammation during the normal immune response but also during the development of CNS pathologies including EAE and MS [129,130]. Activated microglia are involved in neuroinflammation because they represent the major antigen-presenting cells expressing class I and II MHC and costimulatory proteins in the CNS [131]. Instead, attenuation of microglial activation has been related to a reduced axonal injury in EAE [132,133].
The role of T cells in the pathogenesis of Parkinson's disease
2018, Progress in NeurobiologyCitation Excerpt :As previously reported, microglia are responsible for myelin debris removal and digestion, which are key steps in antigen processing and presentation to T cells in EAE (Huizinga et al., 2012). Once activated, APCs are recruited, present myelin antigens through MHC class II molecules and, thus, are capable of further activating infiltrating T cells (Almolda et al., 2010; Aloisi et al., 1998; Matyszak et al., 1999). In addition, macrophages have been found in the perivascular space, the choroid plexus, and the meningeal spaces of the CNS (Fabriek et al., 2005; Ge et al., 2017; McMenamin, 1999; McMenamin et al., 2003; Park et al., 2017; Schain et al., 2018; Wasser et al., 2016).
Staining of HLA-DR, Iba1 and CD68 in human microglia reveals partially overlapping expression depending on cellular morphology and pathology
2017, Journal of NeuroimmunologyCitation Excerpt :Overlap was the least between HLA-DR and Iba1. This incomplete overlap was also shown in the spinal cord of rat experimental autoimmune encephalomyelitis (EAE), an animal model of MS (Almolda et al., 2010). These authors suggested that some Iba1+ cells did not yet express HLA-DR due to their activation state.
GM-CSF: An immune modulatory cytokine that can suppress autoimmunity
2015, CytokineCitation Excerpt :As an example, microglia, the macrophages of the brain, have been derived ex vivo with astrocyte-conditioned media and GM-CSF [28]. Additionally, microglial cells have also been shown to acquire dendritic cell phenotype in models of experimental autoimmune encephalomyelitis (EAE) [29]. Likewise, GM-CSF amplifies IL-3-induced differentiation of basophils from bone marrow cells [30], suggesting a possible role as a growth factor for basophil precursors.
Berberine: A natural modulator of immune cells in multiple sclerosis
2024, Immunity, Inflammation and DiseaseTransient Receptor Potential Vanilloid 4-Dependent Microglial Function in Myelin Injury and Repair
2023, International Journal of Molecular Sciences