Competitive PCR quantification of pro- and anti-inflammatory cytokine mRNA in the central nervous system during autoimmune encephalomyelitis

Differential role of TNF-alpha and IFN-gamma in the brain of rats with chronic relapsing autoimmune encephalomyelitis

To elucidate the mechanisms of relapses of the clinical signs in experimental autoimmune encephalomyelitis (EAE), the cytokine profile of chronic relapsing EAE (CR-EAE) in rats was determined by competitive polymerase chain reaction (PCR). By immunization with guinea pig spinal cord homogenate and treatment with low-dose cyclosporin A (CsA), rats developed two attacks of EAE with remission in between. Cytokine analysis revealed that the level of TNF-alpha mRNA increased at the first and second attacks with transient disappearance at the remission phase. In contrast, the level of IFN-gamma mRNA was suppressed at the first attack by CsA and peaked at the second attack. Intraventricular administration of IFN-gamma prior to onset of disease signs induced more relapses, or a severe lethal form. In addition, the intraventricular injection of TNF-alpha caused the persistence of the clinical signs. These findings suggest that TNF-alpha contributes to the first and second attacks of CR-EAE, while IFN-gamma is not required for the first attack but is closely related to the relapse of the disease. With regard to anti-inflammatory cytokines, the levels of both TGF-beta1 and IL-10 mRNA at the second attack were higher than those at the first attack. Taken together, differential involvement of TNF-alpha and IFN-gamma is closely associated with the clinical features of CR-EAE.

CD40-CD154 Interaction and IFN-γ Are Required for IL-12 But Not Prostaglandin E2 Secretion by Microglia During Antigen Presentation to Th1 Cells

IL-12 and PGE2 promote and inhibit, respectively, the development of Th1 responses. Production of these mediators by APC residing in the central nervous system (CNS) may be involved in the local regulation of the T cell phenotype during infectious and autoimmune CNS diseases. In the present study we have examined IL-12 and PGE2 secretion by cultured microglia and astrocytes from the mouse brain upon Ag-dependent interaction with I-Ad-restricted, OVA323–339 specific TCR transgenic Th1 and Th2 cell lines. We show that microglia, which restimulate efficiently both Th1 and Th2 cells, secrete IL-12 upon Ag-dependent interaction with Th1, but not with Th2 cells. Th1-driven IL-12 production depends on TCR ligation by MHC class II/peptide complexes, CD40 engagement on microglia, and IFN-γ secretion by activated Th1 cells. Th1 and, to a lesser extent, Th2 cells also stimulate the production of PGE2 by microglia. T cell-mediated induction of PGE2 requires MHC class II/peptide/TCR interactions but does not depend on CD40 engagement or on the presence of IFN-γ. Astrocytes, which preferentially activate Th2 cells, fail to produce IL-12 and secrete negligible amounts of PGE2 upon interaction with either Th1 or Th2 cells. These results suggest that during CNS infection or immunopathology, IL-12 produced by microglia upon Ag-specific interaction with Th1 cells may further skew the immune response to Th1, whereas the T cell-dependent production of PGE2 by microglia may represent a negative feedback mechanism, limiting the propagation of Th1 responses.

Persistent Expression of Experimental Autoimmune Encephalomyelitis (EAE)-Specific Vβ8.2 TCR Spectratype in the Central Nervous System of Rats with Chronic Relapsing EAE

Monitoring the TCR repertoire is indispensable for the assessment of T cell-associated autoimmune diseases and subsequent TCR-based immunotherapy. In the present study, we examined the TCR repertoire of spinal cord T cells of Lewis rats by CDR3 spectratyping during chronic relapsing experimental autoimmune encephalomyelitis (EAE) induced by immunization with spinal cord homogenate. It was found that Vβ8.2 spectratype with the shortest CDR3 expanded oligoclonally throughout the course of the disease. In addition, Vβ12 spectratype expansion was observed at the first and second attacks of EAE. Sequence analysis revealed that clones with the DSSYEQYF sequence, which is a representative sequence of myelin basic protein (MBP)-reactive T cell clones, constituted the predominant population in the Vβ8.2 family. Surprisingly, Vβ12 also used the identical amino acid sequence in the CDR3 region. These findings indicate that although infiltrating T cells in the central nervous system are activated polyclonally, the TCR repertoire remains unchanged throughout the course. Moreover, the finding that the predominant CDR3 amino acid sequence of Vβ8.2 and Vβ12 spectratypes is identical with that of MBP-induced EAE suggests that a single Ag in spinal cord homogenate, possibly MBP, is involved in disease development.

Lack of Th2 cytokine increase during spontaneous remission of experimental allergic encephalomyelitis

The mechanisms underlying spontaneous remission of autoimmune diseases are presently unknown, though regulatory T cells are believed to play a major role in this process. We tested the hypothesis that Th2 and/or other T cell regulatory cytokines cause the spontaneous remission of experimental allergic encephalomyelitis (EAE), a model of Th1-mediated autoimmunity. We analyzed the cytokine profile of lymph node and central nervous system-infiltrating cells in individual SJL mice at different stages of proteolipid protein (PLP) 139-151 peptide-induced EAE. We found that IFN-gamma slowly fades away after clinical recovery, whereas IL-4, IL-10 and transforming growth factor-beta remain low or undetectable. Our peptide-results therefore suggest that regulatory T cells producing anti-inflammatory cytokines are not involved in spontaneous remission of EAE and challenge the view that the Th1/Th2 balance has a key role in EAE regulation.

Differential Expression of Inflammatory Cytokines Parallels Progression of Central Nervous System Pathology in Two Clinically Distinct Models of Multiple Sclerosis

Multiple sclerosis is an immune-mediated demyelinating disease of unknown etiology that presents with either a chronic-progressive or relapsing-remitting clinical course. Theiler’s murine encephalomyelitis virus-induced demyelinating disease (TMEV-IDD) and relapsing-remitting experimental autoimmune encephalomyelitis (R-EAE) in the SJL/J mouse are both relevant murine CD4+ T cell-mediated demyelinating models that recapitulate the multiple sclerosis disease phenotypes. To determine the cellular and molecular basis for these observed differences in clinical course, we quantitatively analyzed the temporal expression of pro- and antiinflammatory cytokine mRNA expression in the central nervous system (CNS) and the phenotype of the inflammatory mononuclear infiltrates. TMEV-infected SJL/J mice expressed IFN-γ, TNF-α, IL-10, and IL-4 mRNA during the preclinical phase, and their levels continued to increase throughout the duration of the chronic-progressive disease course. These data correlated with the continued presence of both CD4+ T cells and F4/80+ macrophages within the CNS infiltrates. In contrast, SJL/J mice with PLP139–151-induced R-EAE displayed a biphasic pattern of CNS expression for the proinflammatory cytokines, IFN-γ and TNF-α, with expression peaking at the height of the acute phase and relapse(s). This pattern correlated with dynamic changes in the CD4+ T cell and F4/80+ macrophage populations during relapsing-remitting disease progression. Interestingly, IL-4 message was undetectable until disease remission(s), demonstrating its potential role in the intrinsic regulation of ongoing disease, whereas IL-10 was continuously expressed, arguing against a regulatory role in either disease. These data suggest that the kinetics of cytokine expression together with the nature of the persistent inflammatory infiltrates are major contributors to the differences in clinical course between TMEV-IDD and R-EAE.

Diagnosis and assessment of preclinical and clinical autoimmune encephalomyelitis using peripheral blood lymphocyte TCR

In organ-specific autoimmune diseases, T cells involved in the disease development bear a particular type of TCR and infiltrate the target organ predominantly. However, it is difficult to identify disease-inducing T cells in peripheral blood lymphocytes (PBL) because such T cells are very few in number in a large pool of unrelated T cells. In the present study, we demonstrate that CDR3 spectratyping can identify experimental autoimmune encephalomyelitis (EAE)-specific patterns (oligoclonal expansion of Vbeta8.2 with the shortest CDR3) in PBL at the preclinical and clinical stages of acute EAE. Analysis of nucleotide and predicted amino acid sequences of Vbeta8.2 CDR3 of spectratype-derived clones revealed that CASSDSSYEQYFGPG, which is one of the representative sequences of encephalitogenic T cell clones, constituted the predominant population in both PBL and spinal cord T cells. In chronic relapsing EAE, the EAE-specific spectratype pattern in PBL was observed during the 1 st and 2nd attacks, but not at the remission and full recovery stage. These findings indicate that the spectratyping pattern in PBL reflects the disease activity of acute and chronic relapsing EAE. Thus, CDR3 spectratyping using PBL can be used for diagnosis and assessment of T cell-mediated autoimmune diseases and is applicable to human autoimmune diseases.

Semantics, inflammation, cytokines and common sense

Semantic evaluation of some of the terms we regularly employ--inflammation, anti-inflammatory, pro-inflammatory, anti-inflammatory drugs, cytokines, homeostasis and stress--raises concerns about their precise meanings and about their mechanistic implications. Semantic imprecision may have undesirable conceptual consequences.

Cytokine expression by inflammatory cells obtained from the spinal cords of Lewis rats with experimental autoimmune encephalomyelitis induced by inoculation with myelin basic protein and adjuvants

Inflammatory cells were obtained from the spinal cords of rats with acute experimental autoimmune encephalomyelitis (EAE) induced by inoculation with myelin basic protein (MBP) and adjuvants. Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to investigate the expression of mRNA for interleukin-2 (IL-2), IL-4, IL-10 and interferon-gamma (IFN-gamma) by cells from groups of rats studied 10-21 days after inoculation. On all days of study, the inflammatory cells, which were predominantly lymphocytes, expressed mRNA for IL-2, IL-4, IL-10 and IFN-gamma. In the mRNA from normal rat spinal cord tissue, there was little expression of cytokine mRNA. Cells from a short-term MBP-reactive T cell line expressed all the cytokines. Densitometry was used to measure the products of PCR, to assess the expression of each cytokine relative to that of beta-actin. IL-2 mRNA was expressed throughout the course of disease and reached a peak on day 18, during late clinical recovery. IFN-gamma was expressed throughout the course of the disease and was also high during late recovery. IL-4 mRNA was present in the spinal cord throughout the course of the disease, with a slight rise during late recovery. Relative expression of IL-10 rose to a peak on days 17-19, during late recovery from clinical disease. This study indicates that IL-2, IL-4, IL-10 and IFN-gamma are expressed by inflammatory cells in the spinal cord in EAE, with the relative expression of all cytokines being high during late clinical recovery.

Quantitative analysis of pro- and anti-inflammatory cytokine mRNA in neural graft rejection

The central nervous system (CNS) has been considered an immunologically privileged site. However, this concept is now changing because rejection of histoincompatible neural grafts is commonly observed in the CNS. To be able to use neural transplantation as therapy for human diseases, it is important to determine factors that are related to brain-graft rejection. In the present study, we examined the phenotype of infiltrating T cells around grafts in the cerebra that had received xenogeneic (mouse to rat) neural transplants. Furthermore, the amount of pro- and anti-inflammatory cytokine mRNA was determined by competitive PCR at various time points after the neural transplantation. Immunohistochemical examination revealed that both CD4-positive and CD8-positive T cells infiltrated the CNS parenchyma. In competitive PCR analysis, levels of IFN-gamma and perforin in xenografts on days 10 and 13 post-transplantation (PT) were higher than those in isografts (rat to rat) at the same stage, whereas the levels of TNF-alpha, which was detected only on day 7 PT, were not significantly different between the two groups. With regard to anti-inflammatory cytokines, TGF-beta1 mRNA was recognized throughout the examination period, but there was no significant difference between xeno- and iso-grafts at most time points. These findings suggest that IFN-gamma and perforin secreted by infiltrating CD4-positive and CD8-positive T cells, respectively, play an important role in neural graft rejection. The responses of anti-inflammatory cytokines seem to be nonspecific reactions to grafts or surgical procedures.

The Effect of γδ T Cell Depletion on Cytokine Gene Expression in Experimental Allergic Encephalomyelitis

In experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis, we showed previously that depletion of γδ T cells using the mAb GL3 immediately before disease onset, or during the chronic phase, significantly ameliorated clinical severity. We now report on the effect of γδ T cell depletion on expression of five cytokine genes, IL-1, IL-6, TNF, lymphotoxin, and IFN-γ in spinal cords of mice during the pre-onset, onset, height, and recovery phases of EAE, and on expression of type II nitric oxide synthase. In control animals, the mRNAs for IL-1 and IL-6 rose dramatically at disease onset and peaked before disease height, whereas the mRNAs for TNF, lymphotoxin, and IFN-γ rose more slowly and peaked with peak of disease. In GL3-treated animals, a dramatic reduction in all five cytokines was noted at disease onset, but only IFN-γ remained significantly reduced at a time point equivalent to height of disease in control animals. ELISA data confirmed the reduced levels of IL-1 and IL-6 at disease onset in GL3-treated animals, and pathologic analysis demonstrated a marked reduction in meningeal infiltrates at the same time point. Studies of type II NOS also demonstrated a significant reduction in both mRNA and protein expression at the height of disease in GL3-treated animals. These results suggest that γδ T cells contribute to the pathogenesis of EAE by regulating the influx of inflammatory cells into the spinal cord and by augmenting the proinflammatory cytokine profile of the inflammatory infiltrates.

TGF-beta in the central nervous system: potential roles in ischemic injury and neurodegenerative diseases

The Transforming Growth Factor-betas (TGF-beta) are a group of multifunctional proteins whose cellular sites of production and action are widely distributed throughout the body, including the central nervous system (CNS). Within the CNS, various isoforms of TGF-beta are produced by both glial and neural cells. When evaluated in either cell culture or in vivo models, the various isoforms of TGF-beta have been shown to have potent effects on the proliferation, function, or survival of both neurons and all three glial cell types, astrocytes, microglia and oligodendrocytes. TGF-beta has also been shown to play a role in several forms of acute CNS pathology including ischemia, excitotoxicity and several forms of neurodegenerative diseases including multiple sclerosis, Parkinson's disease, AIDS dementia and Alzheimer's disease.