Resistance and susceptibility to experimental autoimmune neuritis in Sprague-Dawley and Lewis rats correlate with different levels of autoreactive T and B cell responses to myelin antigens

Experimental autoimmune neuritis (EAN) is a CD4⁺ T cell-mediated, inflammatory demyelinating disease of the peripheral nervous system (PNS) that serves as a model for Guillain-Barré syndrome (GBS) in humans. Various mouse and rat strains show different susceptibilities to EAN that can be induced by immunization with bovine PNS myelin (BPM) + Freund's complete adjuvant (FCA). We examined PNS-induced T and B cell responses and cytokine protein production as well as mRNA expression to study the mechanisms behind susceptibility to EAN in Lewis rats and resistance in Sprague-Dawley (SD) rats. Lewis rats with EAN have elevated PNS myelin-reactive interferon-γ (IFN-γ) production, TNF-α mRNA expression, and increased B cell responses to PNS myelin antigens, but low PNS myelin-reactive transforming growth factor-β (TGF-β) and interleukin (IL)-10 mRNA expression in lymph node mononuclear cells (MNC). In contrast, resistance to EAN in SD rats is associated with reduced BPM and P2 peptide-reactive IFN-γ production, TNF-α mRNA expression, and suppressed B cell responses to PNS myelin antigens as well as up-regulation of TGF-β and IL-10 mRNA expression. Resistance to EAN is also associated with low-grade inflammation or absence of histological evidence of EAN. These results suggest that differential autoreactive T and B cells responses to PNS myelin antigens are strain specific, and the susceptibility to EAN is related to quantitative rather than qualitative differences in distribution between pro-inflammatory and anti-inflammatory cytokines. J. Neurosci. Res. 54:373–381, 1998. © 1998 Wiley-Liss, Inc.     

Interferon γ, interleukin 4 and transforming growth factor β in experimental autoimmune encephalomyelitis in lewis rats: Dynamics of cellular mrna expression in the central nervous system and lymphoid cells

The potential role of certain important immunoregulatory and effector cytokines in autoimmune neuroinflammation have been studied. We have examined the expression of mRNA, with in situ hybridization, of interferon -γ (IFN-γ), interleukin 4 (IL-4) and transforming growth factor β (TGF-β) both in sections of spinal cords and the antigen-induced expression of these cytokines by lymphoid cells after stimulation with a dominant encephalitogenic peptide of MBP (MBP 63–88) during the course of actively induced experimental autoimmune encephalomyelitis (EAE) in Lewis rats. In spinal cords, the target organ in EAE, cells expressing mRNA for IFN-γ, first appeared at the onset of clinical signs, i.e., day 10 postimmunization (p.i.), peaked at the height of disease (day 13 p.i.), and then gradually decreased concomitant with recovery. Very few IL-4 mRNA-expressing cells appeared in the spinal cord with no clear relation to clinical signs or histopathology. In contrast, expression of mRNA for TGF-β did not increase until day 13 p.i., at height of the disease, shortly preceding recovery. These data are consistent with a disease upregulating role of IFN-γ, while TGF-β may act to limit central nervous system (CNS) inflammation. In lymphoid organs, primed MBP 63–88 reactive T cells showed an interesting time-dependent evolution of their cytokine production in vitro. Thus, early after immunization there was a conspicuous MBP 63–88-induced production of both IFN-γ and IL-4. Such cells may act in the initiation and promotion of the disease. Later, in the recovery phase, MBP 63–88 induced lymphoid cells to TGF-β production. Thus, an autoantigen-specific production of TGF-β occurred during EAE and hypothetically such a mechanism may serve to downregulate aggressive autoimmunity systemically. © 1995 Wiley-Liss, Inc.     

丙戊酸对实验性自身免疫性神经炎大鼠保护作用的机制

目的观察丙戊酸(VAP)对实验性自身免疫性神经炎(EAN)大鼠的保护作用及其机制。方法实验大鼠随机分为VAP高剂量组、VAP低剂量组、EAN模型组、正常组,应用P2 57-81多肽与完全弗氏佐剂的混合液诱导EAN模型。VAP于免疫当天至第15d每天腹腔内注射。观察各组大鼠发病情况和坐骨神经组织病理学变化,检测外周血中Th17细胞和Foxp3+Treg细胞含量,检测淋巴结中TNF-α、IFN-γ、IL-17、TGF-βmRNA表达。结果 VAP高剂量组的最初发病时间迟于EAN组(P<0.05),其高峰期临床评分显著低于EAN组(P<0.05),坐骨神经炎性细胞浸润较EAN组明显减少;VAP高剂量组和低剂量组外周血中Th17细胞比例较EAN组显著减少(P<0.05),Foxp3+Treg细胞比例较EAN组显著增加(P<0.05),淋巴结中促炎细胞因子TNF-α、IFN-γ及IL-17mRNA表达与EAN组比较明显下降(P<0.05),VAP高剂量组抑炎细胞因子TGF-βmRNA表达与EAN组比较明显升高(P<0.05)。结论 VAP对EAN有治疗作用,这种作用可能与其能够增加Foxp3+Treg细胞和抑炎细胞因子TGF-β含量、减少TH17细胞含量和促炎细胞因子的表达有关。     

Multiple sclerosis: myelin basic protein induced mRNA expression of proinflammatory cytokines in mononuclear cells is suppressed by interferon-β 1b in vitro

Beta-interferon (IFN-β) is a promising treatment in multiple sclerosis (MS), reducing the exacerbation rate and MRI lesion burden, as well as the disease progression in relapsing-remitting MS. IFN-β was originally defined by its antiviral effects, but the interest has recently been focused on its immunomodulatory properties. Myelin basic protein (MBP) is one of several autoantigens considered to be the target for autoaggressive immune responses, which eventually might lead to the development of MS. To study in-vitro effects of IFN-β1b on MBP induced cytokine expression, mRNA for the Th1 cytokines IFN-γ and TNF-α, the Th2 related IL-4 and IL-6, the cytolytic perforin and the immune response downregulating TGF-β was measured with in situ hybridization after culture of blood mononuclear cells (MNC) in the presence and absence of MBP. Numbers of cells expressing IFN-γ, TNF-α, perforin and IL-4 mRNA were significantly suppressed after culture with 10 U/ml IFN-β1b. No such effect was seen on MBP induced IL-6 or TGF-β mRNA expression. These observations suggest that one of the major effects of IFN-β1b is the induction of a shift in the cytokine mRNA profile towards a more immunosuppressive pattern. In parallel in vitro tests, the control substance dexametasone (40 μg/ml) reduced the numbers of cells expressing mRNA for all cytokines under study with the exception of TGF-β, to an extent equal to or even more pronounced than IFN-β1b.     

从IFN-γ／IL-33表达变化探讨EAN中的Th1／Th2细胞极化

目的探讨IFN-γ／和IL-33在实验性自身免疫性神经炎（EAN）发病机制中的作用及EAN中的Th1／Th2细胞极化。方法用P253-78肽段免疫Lewis大鼠,建立EAN模型,观察其发病情况和组织病理改变,并检测淋巴细胞增值反应,用RT-PCR技术检测干扰素γ（IFN-γ）和白介素33（IL-33）在大鼠发病高峰期脾脏、淋巴结和坐骨神经中的表达。结果EAN组大鼠临床表现明显,病理检查可见大量炎性细胞浸润;坐骨神经组织、淋巴结,脾脏中IFN-γ mRNA表达显著升高,IL-33mRNA表达明显减少,其引流淋巴结淋巴细胞对P253-78aa的刺激发生强烈的淋巴细胞增殖反应。结论IFN-γ对EAN发病起促进作用,IL-33对EAN大鼠起保护作用;EAN中Th0细胞向Th1的转化明显增强而向Th2细胞的转化则受到抵制。     

趋化因子mRNA在实验性变态反应性神经炎中表达的研究

目的:实验性变态反应性神经炎(EAN)是一类T细胞介导的周围神经系统的自身免疫病,可用牛坐骨神经加完全氟氏佐剂诱导而成。本文研究趋化因子mRNA在实验性变态反应性神经炎(EAN)中的表达并探索其可能的作用。方法:用兔坐骨神经匀浆免疫Wistar大鼠,诱导格林巴利综合症(GBS)的动物模型EAN;采用地高辛标记的寡核苷酸探针检测EAN病变神经组织浸润细胞上趋化因子单核细胞趋化蛋白-1(MCP-1)及巨噬细胞炎性蛋白-1β(MIP-1β)mRNA表达情况。结果:MCP-1mRNA在临床症状出现前1-2天(14天)水平最高,随后逐渐下降;MIP-1 βmRA在临床症状出现前1-2天水平开始升高,在临床症状达到高峰时(21天)最高,进入恢复期后降至基础水平。结论:趋化因子在EAN的炎性细胞迁移及浸润进入神经细胞过程中起到重要作用。     

Effect of transforming growth factor-β1 and -β2 on Schwann cell proliferation on neurites

Mechanisms regulating Schwann cell proliferation during development are unclear. Schwann cell division is known to be driven by an unidentified mitogen present on the surface of axons, but it is not known whether other molecules play a role in regulating this proliferation. Transforming growth factor-beta (TGF-β) which is found in the developing peripheral nervous system (PNS) and is mitogenic for neuron-free Schwann cells in vitro could be involved. We have investigated the effects of TGF-β 1, TGF-β 2 and antibodies to TGF-β and TGF-β 2 on axon driven Schwann cell proliferation. Rat embryonic dorsal root ganglion neurons (DRG) neurons and Schwann cells from the sciatic nerve were isolated, purified and recombined in vitro. Confirming earlier reports by others, we observed that TGF-β 1 and TGF-β 2 added to the culture medium stimulated the proliferation of Schwann cells in the absence of neurons. However, when added to neuron-Schwann cell co-cultures, TGFβ caused a variable response ranging from no effect to moderate inhibition of Schwann cell proliferation in different experiments. A stimulation of Schwann cell proliferation by TGFβ was never observed in neuron-Schwann cell co-cultures. Antibodies to TGF-β and TGF-β 2 did not influence axon driven Schwann cell proliferation. To further determine the role of TGF-β in Schwann cell proliferation and myelination, we studied Schwann cell proliferation in cultures from mice in which the TGF-β 1 gene was delected by homologous recombination. Neuron-Schwann cell cultures from wild-type, heterozygous and homozygous mice were used. No differences were observed in either Schwann cell proliferation or myelination between cultures obtained from homozygous mutants and their heterozygous and wild-type controls. These findings suggest that TGF-β does not function as a part of the mitogenic mechanism presented by neurons to Schwann cells, but that the presence of active TGFβ in the cellular environment might regulate the degree of proliferation induced by neuronal contact. Copy 1995 Wiley-Liss, Inc.     

Tumor necrosis factor-α in immune-mediated demyelination and Wallerian degeneration of the rat peripheral nervous system

This study reports on the immunocytochemical localization of tumor necrosis factor-alpha (TNFα) in immune-mediated demyelination and Wallerian degeneration of the rat peripheral nervous system (PNS) using teased nerve fiber preparations. In experimental autoimmune neuritis induced by active immunization (EAN) or by adoptive transfer of autoreactive T cells (AT-EAN), macrophages passing blood vessels as well as macrophages adherent to nerve fibers were TNFα-positive. Large post-phagocytic macrophages at later stages of demyelination were TNFα-negative. Intraperitoneal application of an anti-TNFα antibody to EAN rats significantly reduced the degree of inflammatory demyelination, suggesting a pathogenic role for TNFα. After nerve transection only macrophages located within degenerating nerve fibers were TNFα-positive, while those entering and leaving nerves were negative. TNFα produced by macrophages seems to bevolved in immune-mediated demyelination and non-immune myelin degradation after axotomy. While interferon-gamma (IFNγ) is present in EAN nerves and may act as a local stimulus for TNF expression, the nature of this signal in Wallerian degeneration in the absence of IFNγ is unknown.     

从Th1、Th17细胞极化探讨iMDC负载P258-73肽段干预EAN的机制

目的 观察未成熟髓源树突状细胞负载P258-73肽段干预实验性自身免疫性神经炎的效果,及干预对IL-17、IFN-γ mRNA表达的影响,从Th1、Th17细胞极化的角度探讨其干预机制.方法 P258-73aa负载于体外培养的iMDC,获得P258-73aa-iMDC,用P253-78aa和CFA免疫Lewis大鼠制成EAN动物模型,免疫前7d各组大鼠分别给予PBS、iMDC及P258-73aa-iMDC干预.观察发病情况并作临床评分及病理改变.收集引流淋巴结细胞检测淋巴细胞增殖反应,RT-PCR技术检测大鼠脾脏、淋巴结和坐骨神经中IL-17、IFN-γ mRNA的表达.结果 P258-73aa-iMDC干预组大鼠的平均临床评分、抗原特异性淋巴细胞增殖反应和坐骨神经炎性细胞浸润均降低;IFN-γ 及IL-17 mRNA在脾脏、淋巴结和坐骨神经中的表达也明显降低.结论 P258-73aa-iMDC通过影响IL-17、IFN-γ 的分泌,影响Th1、Th17细胞极化,抑制抗原特异性淋巴细胞增殖,从而减轻EAN的发病,这可能是其诱导免疫耐受的机制之一.

Abstract：

Objective To explore the improving potential of immature myeloid dendritic cell (Imdc) pulsed with P258-73aa peptide (P258-73aa-Imdc) in experimental autoimmune neuritis (EAN) ,and to explore the role of Th1/Th17 cells polarization in this tolerance therapy by detecting the expression of IL-17 and IFN-γ mRNA. Methods P258-73aa21 was pulsed with Imdc in vitro to get P258-73aa-iMDC. Rats of each group were immunized with P253-78aa and CFA. 7 days before immunization, each group was injected with PBS or iMDC or P258-73aa-iMDC respectively. Clinical scores of each group and histopathological changes were evaluated and the lymphocyte proliferation response was assayed; IL-17 and IFN-γ mRNA in spleen,lymph node and sciatic nerves were measured by RT-PCR. Results The P258-73aa-iMDC interferred group had lower average clinical score and suppressed antigen specific lymphocyte proliferation, as well as milder infiltration by the inflammatory cells in sciatic nerves. Meanwhile, the expression of IL-17/IFN-γ mRNA in spleen, lymph node and sciatic nerves were also decreased. Conclusion The protective effect of P258-73aa-iMDC could be associated with the inhibition of lymphocyte proliferation and IL-17, IFN-γ through the polarization of Th1/Th17 cells,which is probably one of the tolerance mechanism of P258-73aa-iMDC in EAN.     

Cytokine profile in interferon-β treated multiple sclerosis patients: reduction of interleukin-10 mRNA expressing cells in peripheral blood

Treatment with interferon-β reduces relapse rate, slows progression of neurological disability and reduces the number of active brain lesions observed with magnetic resonance imaging in relapsing-remitting multiple sclerosis. Interferon-β has antiviral properties, but in addition it affects the expression of several immunoregulatory genes, including genes for cytokines such as interferon-γ and interleukin-10. Cytokines are believed to be central in the pathologic process in multiple sclerosis, by regulating autoreactive T- and B-cell responses. In this study we have determined effects of interferon-β on the frequency of cells in peripheral blood and cerebrospinal fluid expressing mRNA for interferon-γ, tumor necrosis factor-α, interleukin-4 and interleukin-10 in a group of multiple sclerosis patients. All patients were treated for two months or more, since the beneficial effect of interferon-β is not apparent until after several months of treatment. We detected a significant reduction of interleukin-10 mRNA expressing cells in the peripheral blood during interferon-β treatment compared with pretreatment values (10 vs 33 cells/10⁵; p = 0.028) while the other investigated cytokines were not significantly affected. We conclude that there is a long term effect of interferon-β on cytokine expression in multiple sclerosis patients. Its relation to the therapeutic effect is as yet not clear.     

B cells play a cooperative role via CD40L-CD40 interaction in T cell-mediated experimental autoimmune neuritis in Lewis rats

The expression of co-stimulatory molecules CD40 and CD40L was examined over the course of experimental autoimmune neuritis (EAN) induced in Lewis rats by immunization with bovine peripheral nerve myelin. In draining lymph nodes, highest level of CD40L expression was seen on day 7 post immunization (p.i.), i.e. before onset of clinical signs of EAN, while CD40 expression was increased on day 14 p.i., i.e. at peak of clinical disease. In contrast, both CD40 and CD40L expressing cells in sciatic nerves, a target organ of EAN, peaked on day 14 p.i., large numbers of both expressing cells were mainly detected on day 14-21 p.i. After co-culture with EAN rat B cells bearing CD40, P0 peptide 180-199-specific T cell line cells exhibited a rapid down-regulation of CD40L expression. Furthermore, EAN rats had enhanced P0 peptide 180-199-specific antibody responses on day 14 p.i., which might have contributed to their aggravated EAN and further demonstrated the role of antibodies in EAN. The results indicate that CD40L-CD40 interactions are involved in the initiation of the antigen-specific T cell responses associated with the generation and development of EAN, and may mediate autoantibody production in EAN. Evidently, B cells play a cooperative role via CD40L-CD40 interaction in T cell-mediated EAN of Lewis rats.     

Rho激酶抑制剂对OX40及其配体mRNA在实验性变态反应性神经炎中表达的影响

目的 研究Rho激酶(ROK)抑制剂对OX40及其配体(OX40L)mRNA在实验性变态反应性神经炎(experimental allegic neuritis,EAN)大鼠坐骨神经、脾脏、外周血和淋巴结中表达的影响.方法 54只Lewis大鼠随机分为EAN模型组、EAN+ROK抑制剂干预组和完全弗氏佐剂对照(CFA)组.分别在免疫后第9、17、26天处死动物,取其坐骨神经根、脾脏、外周血单个核细胞和淋巴结,采用逆转录PCR(RT-PCR)技术检测OX40和OX40L mRNA在各组织的表达水平.结果 EAN+ROK抑制剂组大鼠OX40 mRNA在坐骨神经中第9、17、26天的表达分别为0.266±0.031、0.298±0.024和0.113±0.018;在淋巴结中第9、17、26天的表达分别为0.453±0.030、0.496±0.100和0.220±0.016;OX40L mRNA在坐骨神经中第9、17、26天的表达分别为0.247±0.018、0.298±0.026和0.165±0.013;在淋巴结中第9、17、26天的表达分别为0.283±0.027、0.306±0.011和0.161±0.012.与EAN组比较,OX40和OX40L mRNA的表达明显降低(t=2.24～4.89,P＜0.05),坐骨神经炎性细胞浸润和脱髓鞘减轻.CFA组大鼠无症状.结论 ROK抑制剂可以减轻EAN发病程度,抑制OX40/OX40L的表达可能是其作用机制之一.     

Suppression of Autoimmune Neuritis in IFN-γ Receptor-Deficient Mice

Experimental autoimmune neuritis (EAN) is an animal model of the human disease Guillain–Barré syndrome. In this autoimmune inflammatory disease, CD4⁺ T cells mediate demyelination in the peripheral nervous system (PNS). Infiltrating macrophages and T cells as well as cytokines like interferon (IFN)-γ are intimately involved in causing pathogenic effects. To investigate the role of IFN-γ in cell-mediated EAN, IFN-γ receptor-deficient mutant (IFN-γR^−/−) C57BL/6 mice and corresponding wild-type mice were immunized with P0 peptide 180–199, a purified component of peripheral nerve myelin, and Freund's complete adjuvant. IFN-γR^−/− mice exhibited later onset of clinical disease. The disease was also less severe than in wild-type mice. Fewer IL-12-producing but more IL-4-producing cells were found in sciatic nerve sections from IFN-γR^−/− mice than from wild-type mice on day 24 postimmunization, i.e., at the peak of clinical EAN. At the same time, IFN-γR^−/− mice had less infiltration of inflammatory cells, including macrophages, CD4⁺ T cells, and monocytes, into sciatic nerve tissue and less demyelination. However, numbers of IFN-γ-secreting cells from the spleen were significantly augmented in the IFN-γR^−/− mice, reflecting a failure of negative feedback circuits. The IFN-γR deficiency did not affect the production of anti-P0 peptide 180–199-specific antibodies. These results indicate that IFN-γ contributes to a susceptibility for EAN in C57BL/6 mice by promoting a Th1 cell-mediated immune response and suppressing a Th2 response.     

Dynamics of production of MIP-1alpha, MCP-1 and MIP-2 and potential role of neutralization of these chemokines in the regulation of immune responses during experimental autoimmune neuritis in Lewis rats.

Experimental autoimmune neuritis (EAN) is an inflammatory autoimmune demyelinating disease of the peripheral nervous system (PNS) and represents an animal model of Guillain-Barré syndrome (GBS), which is a major inflammatory demyelinating disease of the PNS in humans. In the present study, the dynamics of the expression of the chemokines macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-2 and monocyte chemotactic protein-1 (MCP-1) were determined in the sciatic nerves of EAN rats. Additionally, the effect of neutralizing antibodies against MIP-1alpha, MIP-2 and MCP-1 on the clinical course of EAN and the chemokine expression was investigated. The maximum of MIP-1alpha positive cells in the sciatic nerves was seen on day 14 post immunization (p.i.) correlating with the development of severe clinical signs. Administration of an anti-MIP-1alpha antibody suppressed the clinical signs of EAN and inhibited inflammation and demyelination in the sciatic nerve. Peak numbers of MCP-1 positive cells in the sciatic nerves were detected on day 7 p.i. Administration of an anti-MCP-1 antibody caused a delay of onset of EAN. However, 4 of the 6 EAN rats receiving the anti-MCP-antibody showed the same degree of inflammatory cell infiltration and demyelination in the sciatic nerves as sham-treated EAN rats, whereas only 2 EAN rats had less inflammation and demyelination. The numbers of MIP-2 positive cells reached a maximum on day 21 p.i. Anti-MIP-2 antibody failed to suppress the clinical signs of EAN and the inflammation and demyelination in the sciatic nerves. Only administration of the anti-MIP-1alpha antibody resulted in a significant reduction in the number of chemokine (MIP-1alpha)-positive cells and ED1-positive macrophages in the sciatic nerves. The present results demonstrate that MIP-1alpha and MCP-1 may play a role in the immunopathogenesis of EAN, and that MIP-1alpha induced trafficking of inflammatory cells can be inhibited by immunoneutralization. Further elucidation of the regulation and coordination of MIP-1alpha and MCP-1 production may lead to new therapeutic approaches to GBS in humans.     

Increased transforming growth factor-β, interleukin-4, and interferon-γ in multiple sclerosis

The inflammatory nature of multiple sclerosis (MS) implicates the participation of immunoregulatory cytokines, including the T-helper type 1 (Th1) cell–associated interferon-σ (IFN-σ), the Th2 cell–related interleukin-4 (IL-4), and the immune response–downregulating cytokine transforming growth factor-β (TGF-β), but proof for their involvement in MS has been lacking. By adopting in situ hybridization with complementary DNA oligonucleotide probes for human IFN- IL-4, and TGF-β, the expression of mRNA for these cytokines was detected in mononuclear cells (MNC) from blood and cerebrospinal fluids. Strongly elevated levels of MNC expressing all three cytokines were found in peripheral blood and at even higher frequencies in cerebrospinal fluid from untreated patients with MS and optic neuritis, i.e., a common first manifestation of MS, compared with patients with other neurological diseases and healthy subjects. In MS and optic neuritis, IL-4 mRNA expressing cells predominated, followed by TGF-β– and IFN-σ–positive cells. Control patients with myasthenia gravis had similarly elevated levels of IFN-σ and TGF-β mRNA expressing blood MNC but lower numbers of IL-4–positive cells. No or slight disability of MS was associated with high levels of TGF-β mRNA expressing cells, while MS patients with moderate or severe disability had high levels of IFN-σ–positive cells. IFN-σ and TGF-β may have opposing effects in MS, and treatments inhibiting IFN-σ and/or promoting TGF-β might ameliorate MS.     

Glial cell line‐derived neurotrophic factor is expressed by inflammatory cells in the sciatic nerves of Lewis rats with experimental autoimmune neuritis

Neurotrophic factors, including glial cell line‐derived neurotrophic factor (GDNF), have been known to play a role in neuroprotection in the injured peripheral nervous system (PNS). To evaluate the involvement of GDNF in experimental autoimmune neuritis (EAN) pathogenesis, the expression of GDNF in rat sciatic nerves with EAN was studied. Western blot analysis showed that the level of GDNF protein significantly increased 1.8‐fold at the paralytic stage of EAN at day 12 post‐immunization (PI) (p < 0.01), and its level further increased approximately 2.5‐fold at day 21 PI (p < 0.001) in the sciatic nerves of EAN‐affected rats compared with those of control rats, and then declined thereafter at day 28 PI. Immunohistochemical analysis showed that axons and Schwann cells constitutively contained GDNF in normal controls. In sciatic nerves with EAN at day 12 PI, GDNF was immunostained in infiltrating inflammatory cells including macrophages and T cells. Collectively, we postulate that GDNF plays a regulatory role in EAN paralysis. A paradoxical role of inflammatory cells to ameliorate PNS inflammation remains to be further studied in EAN, an animal model of human demyelinating disease.     

Cytokine modulation of murine microglial cell superoxide production

Activated microglia may contribute to two opposite effects during inflammation within the central nervous system: host defense against microorganisms and neuronal injury. Each of these processes may be mediated by the generation of reactive oxygen intermediates by activated microglia. We investigated the effects of two proinflammatory cytokines, interferon (IFN)-β and tumor necrosis factor (TNF)-α, and of the anti-inflammatory cytokine, transforming growth factor (TGF)-β, on murine microglial cell superoxide (O₂) production upon stimulation with phorbol myristate acetate (PMA). Priming of microglia with IFN-β or TNF-α resulted in a dose-dependent enhancement of O₂ release in response to PMA. The priming effects of these two cytokines were additive, suggesting that they acted by independent mechanisms. We also found that IFN-β and TNF-β stimulated the release of bioactive TGF-β and that treatment of microglial cell cultures with TGF-β antagonized the priming effects of IFN-β and TNF-α on O₂ production. The results of this study have implications for understanding the mechanisms by which cytokines and microglia may contribute to host defense as well as to injury of the brain. © 1995 Wiley-Liss, Inc.