T-lymphocyte subsets, functional deficits, and morphology in sciatic nerves during experimental allergic neuritis

Lovastatin attenuates nerve injury in an animal model of Guillain-Barré syndrome

Statins, widely used as clinically effective inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase, exhibit anti-inflammatory properties that may be of therapeutic benefit for the management of some neurological disorders. In this study, a short-term course of lovastatin treatment is shown to markedly inhibit the development of experimental autoimmune neuritis (EAN) in the absence of hepatotoxic or myotoxic complications. Independent of cholesterol reduction, lovastatin treatment prevented EAN-induced peripheral nerve conduction deficits and morphologic nerve injury. Co-administration with mevalonate neutralized the prophylactic effects of lovastatin. When administered therapeutically, lovastatin significantly shortened the disease course. Autoreactive immunity, measured in vitro by myelin-stimulated proliferation of splenocytes, was significantly diminished by in vivo lovastatin treatment. Th1-dominant immune responses, measured by cytokine profiling, however, were not affected by lovastatin. Sciatic nerves of lovastatin-treated immunized rats showed markedly reduced levels of cellular infiltrates. Treating peripheral nerve endothelial monolayers with lovastatin significantly inhibited the in vitro migration of autoreactive splenocytes. Together, these data demonstrate that a short-term course of lovastatin attenuates the development and progression of EAN in Lewis rats by limiting the proliferation and migration of autoreactive leukocytes.

Polygenic control of autoimmune peripheral nerve inflammation in rat

Experimental autoimmune neuritis (EAN) is the principal animal model for Guillain-Barré syndrome (GBS), an inflammatory disease of the peripheral nervous system. Little is known on the genetic regulation of these diseases. We provide the first genetic linkage analysis of EAN. Susceptibility to EAN in a rat F2 population segregated with high levels of anti-PNM IgG, as well as IgG2b and IgG2c isotype levels, which support that disease genes regulate preferential Th1/Th2 differentiation. Linkage analysis demonstrated co-localization of EAN loci with reported susceptibility loci for experimental arthritis and/or encephalomyelitis and a new region on chromosome 17. Further dissection of these loci may disclose disease pathways in GBS.

Amelioration of experimental allergic neuritis by sodium fusidate (fusidin): suppression of IFN-gamma and TNF-alpha and enhancement of IL-10

The immunomodulating antibiotic drug fusidic acid and its sodium salt sodium fusidate (fusidin) ameliorate several organ-specific immunoinflammatory diseases. Because preliminary observations suggest that fusidin may also exert a beneficial effect in Guillain-Barré syndrome (GBS), here we have studied the effects of fusidin on actively induced experimental autoimmune neuritis (EAN) in rats, a known animal model for GBS. Both prophylactic and therapeutic treatment with fusidin (4 mg/rat day ip) markedly ameliorated the clinical course of the disease compared to vehicle-treated animals. The beneficial effects were associated with profound modifications of the capacity of these rats to produce and release pro- and anti-inflammatory cytokines such as IFN-gamma, TNF-alpha and IL-10, which are important in regulating the development of EAN.

Human autoimmune neuropathies

Peripheral nerve diseases are among the most prevalent disorders of the nervous system. Because of the accessibility of the peripheral nervous system (PNS) to direct physiological and pathological study, neuropathies have traditionally played a unique role in developing our understanding of basic mechanism of nervous system injury and repair. At present they are providing new insight into the mechanisms of immune injury to the nervous system. A rapidly growing catalogue of PNS disorders are now suspected to be immune-mediated, and in the best understood of these disorders, the molecular and cellular targets of immune attack are known, and the pathophysiology follows directly from the specific immune injury. This review summarizes the immunologically relevant features of the PNS, then considers selected immune-mediated neuropathies, focusing on pathogenetic mechanisms. Finally, the PNS is providing a testing ground for new immunotherapies and approaches to protection and regeneration, including the use of trophic factors. The current status of treatment and implications for future approaches is reviewed.

Peripheral nervous system (PNS) expression of mRNAs encoding myelin proteins and Fc gamma RIII during experimental allergic neuritis

Experimental allergic neuritis (EAN) was induced in Lewis rats by injection of 'SP26', a peptide homologous to amino acids 53-78 of bovine myelin P2 protein, in complete Freund's adjuvant. The rats developed signs of EAN which began on day 14, were maximal on day 18, and had subsided by day 30. RNA content of cauda equina and sciatic nerves increased more than 2-fold at the height of EAN. Expression of myelin P0 and P1 mRNAs did not fall during EAN, nor rise during recovery. Fc gamma R mRNA, which encodes Fc gamma RIII, an immunoglobulin-binding protein mediating activation of natural killer cells and macrophages by immune complexes, was transiently, but markedly induced in scattered endoneural cells, presumably macrophages, in cauda equina and sciatic nerves during the period of increasing weakness.

Focal conduction block in the dorsal root ganglion in experimental allergic neuritis

Acute experimental allergic neuritis was induced in Lewis rats by inoculation with bovine intradural root myelin and adjuvants. In terminal experiments, sensory conduction was assessed in rats with hindlimb ataxia and weakness by stimulating the exposed sciatic nerve and recording directly from the exposed L-4 spinal nerve, dorsal root ganglion, dorsal root, and dorsal root entry zone. Focal conduction block was present in a high proportion of large-diameter fibers in the dorsal root ganglion. In contrast, nerve conduction in the peripheral nerve and spinal nerve was essentially normal apart from probable conduction block in some fibers in the proximal spinal nerve in a minority of rats. The afferent volley arriving at the dorsal root entry zone of the spinal cord was greatly reduced, as a consequence of the conduction block in the dorsal root ganglion and probable conduction block in the dorsal root. The M wave recorded from the fourth dorsal interosseus muscle of the hindfoot was normal in amplitude but slightly prolonged in latency and the H reflex was absent. These electrophysiological findings correlated well with the histological findings of inflammation and prominent demyelination in the dorsal root ganglia and dorsal roots with minimal involvement of the proximal spinal nerve and no involvement of the sciatic nerve. It is concluded that the hindlimb ataxia in rats with this form of acute experimental allergic neuritis is due to demyelination-induced nerve conduction block in the dorsal root ganglia and probably in the dorsal roots.

Effect of stilbene-type anion channel blockers on the immune response during experimental allergic neuritis (EAN)

We have studied the role of anion channel gating for the autoimmune response in experimental allergic neuritis (EAN) induced by bovine peripheral myelin (BPM). The influence of the stilbene-type anion channel blockers SITS and DIDS on T cell function was assessed by measurement of proliferation and by counting of interferon-gamma (IFN-gamma) secreting cells (IFN-gamma-sc) in response to BPM and phytohemagglutinin (PHA). SITS caused a dose-dependent increase of spontaneous proliferative activity as well as of proliferation in response to the antigenic stimulus BPM. In contrast, the drug caused a decrease of proliferation of cells stimulated with PHA. The number of cells induced to IFN-gamma secretion was reduced by SITS. The suppressive effect was dependent on the degree of activity of cells without drugs. Cultures showing high numbers of BPM reactive T cells were more easily suppressed than cultures with low numbers of BPM reactive T cells. Our results suggest that anion channel gating is involved in the triggering of T cells to IFN-gamma secretion. The anion channel signal pathway in lymphocytes could be a target for pharmacological intervention in inflammatory disorders. In the presently used autoimmune model, EAN, the net effect of in vivo treatment with SITS resulted in worsening of clinical signs and increased inflammatory cell infiltration in sciatic nerve, whereas the in vitro conductivity of sciatic nerve was not significantly affected by the drug. Thus anion channel gating seems to regulate activities of immune cells, and drugs with anion channel blocking properties may have effects that enhance autoimmune disease.

Activated T lymphocyte subsets in experimental allergic neuritis

Changes in activated T cell subsets in peripheral blood were examined during the course of experimental allergic neuritis (EAN), using two-color immunofluorescence flow cytometry. Both CD4+ and CD8+ activated T cells decreased transiently before the onset of clinical signs, and increased just around the time of onset of the disease. In contrast, during the recovery phase, the numbers of CD4+ activated T cells returned to the normal range, whereas CD8+ activated T cells continued to increase. These findings imply that activation of CD4+ helper/inducer cells contributes mainly to the evolution of EAN, and that of CD8+ suppressor cells are necessary for recovery.

Sulfasalazine aggravates experimental autoimmune encephalomyelitis and causes an increase in the number of autoreactive T cells

Sulfasalazine (SASP; 5-(p-(2-pyridylsulfamoyl)phenylazo)salicyclic acid) has beneficial effects on certain inflammatory diseases and has been proposed for clinical trials in multiple sclerosis (MS). We have explored the effects of SASP on actively induced experimental autoimmune encephalomyelitis (EAE) in Lewis rats. SASP was given orally at three different doses from the day of immunization to day 40 post-immunization (p.i.). All doses led to a clinically more protracted disease, increased numbers of T cells infiltrating into the central nervous system (CNS) and to increased numbers of interferon-gamma-secreting cells (IFN-gamma-sc) in the CNS. The effects of SASP treatment on T cell-mediated autoimmunity against CNS myelin and peptides of myelin basic protein (MBP) were measured by IFN-gamma secretion and proliferation by lymph node mononuclear cells in response to these antigens. In SASP-treated rats, increased numbers of IFN-gamma-sc appeared in response to myelin antigens, while the proliferative responses were decreased. We suggest that monitoring cell-mediated immunity with the IFN-gamma-sc method may be relevant for the evaluation of new immunotherapeutic strategies in inflammatory demyelinating diseases. Furthermore, our results demand caution as to clinical trials with SASP in MS.

Early myelin lesions in experimental allergic neuritis

We examined the evolution of demyelination in spinal roots of Lewis rats immunized with whole nerve and complete Freund's adjuvant. Roots were morphologically normal until 11 days after immunization, when we found endoneurial edema and myelin vesiculation in the absence of mononuclear cell contacts. Macrophage-associated myelin stripping was not detected until day 12. Macrophage infiltrations were extensive by day 14, but lymphocytes were sparse. These observations indicate that in experimental allergic neuritis, myelin injury may occur before macrophage-mediated demyelination, and provide support for an early role of serum factors in the development of this disorder.

Oestrogen treatment reduces duration of experimental allergic neuritis in rats and suppresses T cell responses to myelin

The effects of oestrogen and pregnancy on the disease course of experimental allergic neuritis (EAN) in rats were investigated. Pregnant rats were totally protected from EAN and long term 17-beta-oestradiol treatment significantly shortened the disease duration. Lymph node cells from oestrogen treated rats had a suppressed proliferative response when stimulated with myelin or PPD, both when the response was measured immediately after cell preparation and after 72 h cell culture in vitro. Serum levels of IgG antibodies against myelin, P2 or PPD did not differ between treated and non-treated rats although oestrogen treated rats had significantly higher levels of total IgG. Immunohistochemical stainings of nerve roots showed less intensive invasion of T lymphocytes in the oestrogen treated group while immunoreactivity to both class I and II major histocompatibility complex antigens did not differ in between the groups. These findings show that oestrogen ameliorates EAN and suggest that this effect is mediated by suppression of T cell dependent immunity. Factors in addition to oestrogen may be operative during pregnancy when a total protection from EAN is obtained.

T-cell and macrophage activation in experimental autoimmune neuritis and Guillain-Barré syndrome

Evidence implicating cellular immune responses in the pathogenesis of experimental autoimmune neuritis (EAN) and Guillain-Barré syndrome (GBS) is reviewed. In EAN the decisive role of T-lymphocytes in the initiation of immune-mediated nerve damage has been firmly established by adoptive transfer experiments. Macrophages but not Schwann cells express major histocompatibility complex class II gene products in situ and hence may function as antigen presenters. Macrophages are crucial in the amplification and effector phase and damage the myelin sheath by phagocytic attack and release of inflammatory mediators such as toxic oxygen radicals, arachidonic acid metabolites, complement, or hydrolases. Macrophage activation in EAN is achieved by interferon-gamma. Attempts to detect specific sensitization of T-lymphocytes to nerve antigens in patients with GBS have so far been unsuccessful. However, circulating activated T cells can be found in patients with GBS, as evidenced by augmented expression of HLA-DR antigen, the transferrin receptor, and the interleukin-2 receptor on the surface of peripheral blood T cells, and by increased serum concentrations of interleukin-2 and the soluble interleukin-2 receptor. In addition, we present data indicating macrophage activation in GBS.

In vivo treatment of rats with monoclonal antibodies against gamma interferon: effects on experimental allergic neuritis

To elucidate the role of gamma interferon in experimental allergic neuritis (EAN) a mouse monoclonal antibody (DB-1) directed against rat gamma interferon was used to treat rats during different phases of the development of experimental allergic neuritis (EAN). The effects of this treatment were followed by clinical evaluation, and in some instances by immunohistochemical analysis of lymphoid organs and affected nerves for presence of MHC class II antigens and various T cell subsets. DB-1 treatment given after onset of clinical symptoms (Day 15 after immuniozation with myelin) shortened disease duration, compared with non-treated EAN controls. Affected nerves of DB-1 treated animals showed reduced expression of MHC class II antigens and lower numbers of T lymphocytes within the affected nerves. In contrast, when DB-1 treatment was given on the day of immunization (Day 0), the disease duration increased, and when given before onset of the disease (Day 9) the clinical course was not significantly affected. The results support an important role for gamma interferon in the pathogenesis of EAN.

In vivo monoclonal antibody treatment with Ox19 (anti-rat CD5) causes disease relapse and terminates P2-induced immunospecific tolerance in experimental allergic neuritis

The role of CD5+ lymphocytes in the recovery phase and on immunospecific protection against experimental allergic neuritis (EAN) was examined in Lewis rats by in vivo treatment with Ox19, a mouse anti-rat CD5 monoclonal antibody. Animals pretreated with the peripheral nerve basic protein P2 and thereby rendered resistant to the disease showed clinical signs of EAN after intraperitoneal (i.p.) Ox19 injection given at the same time as the rechallenge with neuritogenic doses of myelin in Freund's complete adjuvant. Non-pretreated rats recovered from signs of EAN developed a clinical relapse after i.p. Ox19 injections. Taken together, these data suggest an important regulatory role of the CD5 receptor in the immune response.

Elimination of CD8+ T cells in vivo does not break induced immunospecific tolerance to experimental allergic neuritis in rats

The role of CD8+ T 'cytotoxic/suppressor' T cells in induced immunospecific tolerance and during recovery after actively induced disease was examined by means of elimination of CD8+ cells from Lewis rats using in vivo treatment by Ox8 monoclonal antibodies, in experimental allergic neuritis (EAN). Animals depleted of CD8+ T cells after recovery from EAN did not show any clinical signs of relapse. Other animals were pretreated with the peripheral nerve basic protein P2 and thereby rendered resistant to disease induction with a potentially neuritogenic emulsion. The elimination of CD8+ T cells did not result in EAN here either. Thus, the CD8+ T-cell population does not seem to participate in the suppression of this autoimmune disease under these experimental conditions.

HLA-DR-expressing cells and T-lymphocytes in sural nerve biopsies

Thirty-five sural nerve biopsies were stained immunohistochemically for HLA-DR antigen. HLA-DR was expressed on nonmyelinating Schwann cells, macrophages, vascular endothelium, and perineurium. By means of double immunofluorescence staining the identity of the HLA-DR presenting structures was confirmed. HLA-DR expression was found in all biopsies and thus was not restricted to any particular type of neuropathy. The HLA-DR expression appeared to correlate with severity and activity of the neuropathy. HLA-DR-expressing macrophages wrapping myelinated fibers were prominent in primary demyelinating neuropathies. T-cells were found in 6 out of 15 nerves examined. Their presence correlated with moderate to strong HLA-DR expression of nonmyelinating Schwann cells, and they occurred during active disease.

Modulation of experimental allergic neuritis in rats by in vivo treatment with monoclonal anti T cell antibodies

Monoclonal antibodies (MCA) to different T lymphocyte cell surface antigens have been used to treat rats during different phases of the development of experimental allergic neuritis (EAN). The effects of this treatment were followed by clinical evaluation and in some instances by immunohistochemical analysis of lymphoid organs and affected nerves of the antibody-treated rats. Several MCA, W3/13 (pan T cell reactive), W3/25 (anti-rat CD4), Ox 8 (anti-rat CD8) as well as Ox 6 (anti-Ia) partly prevented clinical signs of EAN when given shortly before expected onset of disease, whereas W3/13 and Ox 8 given at the height of disease did not further affect disease development. However, Ox 19 (anti-rat CD5) given at the same time as immunization partly prevented clinical signs of EAN, while Ox 19 given shortly before expected onset of disease or during height of disease drastically exaggerated disease symptoms. Immunohistochemical studies after Ox 8 or Ox 19 treatment showed a complete absence of staining for the respective antibodies, while staining was preserved with the other MCA. It is concluded that: (1) Ox 8 positive "suppressor/cytotoxic" T lymphocytes do not exert any suppressive effects on EAN during the now investigated phases of disease, and that (2) anti T lymphocyte antibodies (here Ox 19) may exert opposite effects on autoimmune disease when given at different phases of disease development. This may have implications for potential therapeutic trials of MCA therapy for putative autoimmune demyelinating diseases in man.

Induction of class I and class II transplantation antigens in rat brain during fatal and non-fatal measles virus infection

Measles virus induced a marked increase in the expression of MHC-coded class I and class II antigens as detected by immunostaining during both fatal and non-fatal brain infections in rats. The distribution of these molecules in the brain was much more widespread than the occurrence of viral antigen suggesting a soluble factor for their induction. In 14-day-old rats with a non-fatal infection there was a marked infiltration of T lymphocytes of 'cytotoxic/suppressor' phenotype in the brain parenchyma, whereas T 'helper' cell phenotypes mainly were located perivascularly. In brains from newborn rats with a fatal infection no or only few lymphocytes were detected.