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

Soluble TNFR1 inhibits the development of experimental autoimmune neuritis by modulating blood–nerve-barrier permeability and inflammation

The role of TNFalpha/LTalpha during EAN induced by active immunization with peripheral nerve myelin was examined by administering a recombinant soluble chimeric form of human TNF receptor 1 (TNFR1-IgG). TNFalpha and LTalpha do not directly contribute to neurological deficit during EAN since treatment with TNFR1-IgG after onset failed to alter the course of disease. Prophylaxis with a single dose of TNFR1-IgG delayed the onset of EAN and was accompanied initially by inhibition of blood-nerve-barrier permeability and inflammation. Subsequently, the number of infiltrating macrophages and blood-nerve-barrier permeability increased but the disease symptoms remained mild for five days (on average a limp tail) after which severe EAN developed. The antibody titer to peripheral nerve myelin was unaltered by prophylaxis with TNFR1-IgG. The markedly altered tempo of disease onset after TNFR1-IgG prophylaxis indicates that TNFalpha and/or LTalpha have a key role in the development of blood-nerve-barrier permeability and the coupling of macrophage activation and recruitment to peripheral nerve pathology during EAN.

Presence of IFN-gamma does not indicate its necessity for induction of coronary arteritis in an animal model of Kawasaki disease

Kawasaki disease is the most common cause of vasculitis affecting children, and the leading cause of acquired heart disease in the developed world. To date, studies on the role of IFN-gamma in the pathogenesis of Kawasaki disease have focused on peripheral production of IFN-gamma, and have yielded conflicting results. Affected heart tissue is not available from children with Kawasaki disease. In this study, we use an animal model of Kawasaki disease, Lactobacillus casei cell wall extract (LCWE)-induced coronary arteritis, to examine the role of IFN-gamma in the development of coronary artery lesions. We report the presence of IFN-gamma, both at the mRNA and protein levels, in the affected vessels. Its biphasic expression, first at days 3-7 and again at days 28-42 post-LCWE injection, corresponds to the first appearance of inflammatory infiltrate in coronary arteries, and later to vascular wall disruption and aneurysm formation, respectively. Interestingly, ablation of IFN-gamma expression did not dampen the inflammatory response, and IFN-gamma-deficient lymphocytes proliferated more vigorously in response to LCWE than those of wild-type animals. Of more importance, the incidence of coronary arteritis was the same in IFN-gamma-deficient and wild-type mice. Taken together, our findings demonstrate that IFN-gamma regulates the immune response during development of coronary arteritis, but is not required for the induction of coronary artery disease.

Effects of Linomide on immune cells and cytokines inhibit autoimmune pathologies of the central and peripheral nervous system

Linomide (roquinimex, LS 2616) is a quinoline-3-carboxamide with pleiotropic immune modulating capacity and it has therapeutic effects in several experimental animal models of autoimmune diseases. Linomide has been evaluated in clinical trials for multiple sclerosis, and was indeed shown to have disease inhibitory effects. However, due to unexpected side effects recorded in patients treated with Linomide, premature termination of clinical trials was required. The basic mechanism(s) of action of Linomide in inducing beneficial effects in autoimmune diseases is still elusive. Some experimental evidence indicates that Linomide influences the regulation of the cytokine profile, resulting in the inhibition of autoimmune and inflammation pathologies. This review focuses on Linomide applied in models for autoimmune and inflammation pathologies of the central and the peripheral nervous system, and summarises its very encouraging disease inhibitory effects and their potential pharmacological basis. The beneficial effects recorded with Linomide in both experimental and clinical trials emphasise the possible value of substances with Linomide-like activity for clinical use in autoimmune and inflammation pathologies in the near future.

Systemic anti-IFN-gamma treatment and role of macrophage subsets in the foreign body reaction to dermal sheep collagen in rats

The application of a biomaterial induces a foreign body reaction. By controlling this reaction, biocompatibility could be improved. We previously demonstrated that impregnation of a biodegradable biomaterial with antibodies against interferon-gamma (IFN-gamma) inhibits the foreign body reaction. In this study we investigate whether systemic administration of the antibody can induce similar reactions. Several parameters are compared between control and anti-IFN-gamma-treated rats: cellular ingrowth; degradation of the biomaterial; ingrowth of macrophage (MO) subsets, T cells, B cells, NK cells, and granulocytes; and expression of the major histocompatibility complex class II (MHC class II) molecule on antigen presenting cells. Treatment with anti-IFN-gamma results in increased cellular ingrowth and biomaterial degradation and a decreased expression of MHC class II. Overall, systemic treatment with anti-IFN-gamma is insufficient to modulate the foreign body reaction. This suggests an alternative mechanism for MO activation besides IFN-gamma. The role of T cells and MO subsets in the foreign body reaction is discussed.

Linomide suppresses experimental autoimmune neuritis in Lewis rats by inhibiting myelin antigen-reactive T and B cell responses

Linomide (quinoline-3-carboxamide) is a synthetic immunomodulator that suppresses several experimental autoimmune diseases. Here we report the effects of Linomide on experimental autoimmune neuritis (EAN), a CD4+ T cell-mediated animal model of acute Guillain-Barré syndrome (GBS) in humans. EAN induced in Lewis rats by inoculation with bovine peripheral nervous system (PNS) myelin and Freund's complete adjuvant was strongly suppressed by Linomide administered daily subcutaneously from the day of inoculation. Linomide dose-dependently delayed the interval between immunization and onset of clinical EAN, as well as the severity of EAN symptoms. These clinical effects were associated with dose-dependent down-modulation of PNS antigen-induced T and B cell responses and with suppression of the proinflammatory cytokines IL-12, interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha) mRNA. In PNS sections, Linomide suppressed IL-12 and TNF-alpha, and up-regulated IL-10 mRNA expression. These findings suggest that Linomide could be useful in certain T cell-dependent autoimmune diseases.

Inhibition of the tissue reaction to a biodegradable biomaterial by monoclonal antibodies to IFN-gamma

Biomaterials are increasingly used for clinical applications. However, loss of function may occur owing to tissue reactions, which are mainly caused by a variety of inflammatory reactions. Recently, we demonstrated that macrophages (MO) and T cells play key roles in these reactions. Since immunological studies showed that the T cell-derived cytokine interferon-gamma (IFN-gamma) activates MO, the aim of this study was to investigate the possibility of modulating tissue reactions to biodegradable biomaterials by inactivating IFN-gamma. Dermal sheep collagen (DSC) was used as a test biomaterial. DSC impregnated with anti-IFN-gamma or phosphate-buffered saline (control) was implanted in rats. The results showed that cellular ingrowth and formation and function of giant cells were strongly delayed by anti-IFN-gamma. Also, MHC class II expression was strongly inhibited. In the treated DSC, some huge giant cells were formed at the interface but association with the DSC bundles did not occur. Finally, in both the control and treated DSC, T cells and NK cells were rarely detected. This study demonstrates that IFN-gamma plays an important role in the inflammatory reaction to biomaterials. This reaction can be modulated by anti-IFN-gamma, which warrants further studies of anti-IFN-gamma for clinical application to prevent unwanted tissue reactions to biomaterials.

Cytokine production and the pathogenesis of experimental autoimmune neuritis and Guillain-Barré syndrome

Acute inflammatory demyelinating polyradiculoneuropathy (Guillain-Barré syndrome, GBS) and its animal model experimental autoimmune neuritis (EAN) are prototypes of T cell-mediated autoimmune diseases affecting the peripheral nervous system (PNS). Perivascular accumulation of macrophages and T lymphocytes in the PNS, and high levels systemically of PNS myelin antigen-reactive T cells are characteristic features of both diseases, thereby suggesting a pathogenic role for immunoregulatory cytokines. Here we summarise recent studies that have clearly documented that Th1/Th2/Th3 cytokines are differently upregulated during various clinical phases of EAN and GBS. The observations indicate that the role of cytokines in immune regulation and autoimmune disease is more complex than a simple Th1-Th2 dichotomy would suggest. New treatments may be searched for that counteract this complex cytokine imbalance. Treatments with antibodies that selectively target certain pro-inflammatory cytokines, as well as with immunomodulatory preparations that promote cytokines that beneficially influence the disease course should be in focus of future therapeutic trials.

IL-10 suppresses experimental autoimmune neuritis and down-regulates TH1-type immune responses

Experimental autoimmune neuritis (EAN) is a CD4+ T cell-mediated monophasic inflammatory disorder of the peripheral nervous system (PNS). Cellular mechanisms, including macrophage and T cell infiltration, and cytokines like IFN-gamma and TNF-alpha are intimately involved in the pathogenesis of EAN. Interleukin 10 (IL-10) is a TH2-type cytokine that suppresses monocyte and TH1 cell functions. We examined the effect of recombinant human IL-10 (rHuIL-10) in EAN. When administered from the start of immunization with bovine peripheral myelin emulsified in Freund's complete adjuvant, IL-10 effectively suppressed and shortened clinical EAN. Even when given after Day 12 post immunization (pi) after clinical EAN had been established, IL-10 also effectively suppressed the severity of EAN. Pheripheral nerve myelin antigen-reactive IFN-gamma-secreting TH1-like cells were decreased in lymph nodes from IL-10-treated compared to control EAN rats. PNS autoantigen-induced T cell proliferation and B cell responses were not affected. P2 protein-reactive IFN-gamma, TNF-alpha, IL-1 beta, and IL-6 mRNA-expressing lymph node cells were also downregulated in IL-10-treated compared to control EAN rats at Day 14 and 26 pi, while P2-reactive IL-4 mRNA-expressing cells were upregulated throughout treatment. Also, in IL-10-treated EAN rats, upregulated anti-P2 IgG1 and downregulated IgG2a were observed. Our results clearly show that rHuIL-10 can suppress clinical EAN, and this suppression is associated with downregulation of TH1 responses and macrophage function and upregulated TH2 responses.

Interferon-gamma in autoimmunity

Autoimmune disorders are characterized by abrogation of self-tolerance, resulting in emergence of activated self-reactive lymphocyte clones that trigger or maintain inflammatory reactions in specific organs. Interferon-gamma (IFN-gamma), as well as other cytokines, plays an important role as a regulator of the activation of self-reactive lymphocytes and of bystander and accessory cells that are involved in the autoimmune inflammatory response. In experimental models of autoimmunity, endogenous IFN-gamma has invariably been found to profoundly affect the disease course. However, it acts in one way in some diseases and in the opposite way in others.

Immunopathogenesis and treatment of the Guillain-Barré syndrome--Part I

The etiology of the Guillain-Barré syndrome (GBS) still remains elusive. Recent years have witnessed important advances in the delineation of the mechanisms that may operate to produce nerve damage. Evidence gathered from cell biology, immunology, and immunopathology studies in patients with GBS and animals with experimental autoimmune neuritis (EAN) indicate that GBS results from aberrant immune responses against components of peripheral nerve. Autoreactive T lymphocytes specific for the myelin antigens P0 and P2 and circulating antibodies to these antigens and various glycoproteins and glycolipids have been identified but their pathogenic role remains unclear. The multiplicity of these factors and the involvement of several antigen nonspecific proinflammatory mechanisms suggest that a complex interaction of immune pathways results in nerve damage. Data on disturbed humoral immunity with particular emphasis on glycolipid antibodies and on activation of autoreactive T lymphocytes and macrophages will be reviewed. Possible mechanisms underlying initiation of peripheral nerve-directed immune responses will be discussed with particular emphasis on the recently highlighted association with Campylobacter jejuni infection.

Effect of anti-interferon-gamma monoclonal antibody treatment on the development of experimental allergic encephalomyelitis in resistant mouse strains

Immunization with myelin basic protein (MBP) in complete Freund's adjuvant failed to induce experimental allergic encephalomyelitis (EAE) in six resistant mouse strains studied: A/J, BALB/c C3H/HeJ, AKR, NZW and DBA/2. However, treatment of challenged mice with anti-interferon-gamma (IFN-gamma) monoclonal antibody (mAb) induced severe EAE in mice of all strains except AKR. Furthermore, anti-IFN-gamma mAb treatment led to increased disease incidence and severity in BALB/c mice challenged with the MBP peptide87-103, known to be encephalitogenic for the susceptible SJL strain. In three strains tested, anti-IFN-gamma mAb enhanced passively induced EAE in the A/J and C3H/HeJ but not in the BALB/c mice. All mice with clinically overt EAE had widespread histological lesions characterized by mononuclear cell infiltrates and focal demyelination. The results indicate that resistant strains are genetically capable of developing EAE, and that IFN-gamma can contribute to disease resistance.

Neuronal interferon-gamma immunoreactive molecule: bioactivities and purification

An interferon (IFN)-gamma immunoreactive molecule, localized to small neurons in peripheral sensory ganglia (N-IFN-gamma), has been detected with two mouse monoclonal antibodies (DB1 and DB16) directed against different epitopes of rat IFN-gamma. To define N-IFN-gamma with regard to its protein characteristics and bioactivities, DB1 and DB16 were used to purify N-IFN-gamma from rat trigeminal ganglia in a two-step sequential antibody-affinity procedure. Sodium dodecylsulfate polyacrylamide gel electrophoresis (PAGE) and silver staining of purified N-IFN-gamma displayed three bands with an approximate molecular mass of 66, 62 and 54 kDa. The N-IFN-gamma bioactivity was confined to the protein stained on gel when native material was run on PAGE. Biological effects of pure N-IFN-gamma were examined and compared with those of lymphocyte-derived recombinant IFN-gamma. N-IFN-gamma had antiviral effects in vitro and induced major histocompatibility complex class I and II antigens on macrophages and in cells in skeletal muscle cell cultures. N-IFN-gamma also stimulated myoblast proliferation and affected cholinergic receptor distribution on myotubes similar to recombinant IFN-gamma. Both molecules potently stimulated Trypanosoma brucei brucei growth. These data suggest that, although N-IFN-gamma is a protein distinct from lymphocyte-derived IFN-gamma, the two molecules have enough structural similarities to allow for antibody recognition of at least two epitopes, and action on similar target structures on both parasite and mammalian cells.

Influence of K+ channel openers on interferon-gamma dependent immune response in experimental allergic neuritis (EAN)

We examined the influence of the K+ channel opening drugs BRL 38227, pinacidil and diazoxide on cellular immune response and clinical course of experimental allergic neuritis (EAN) actively induced in Lewis rats by bovine peripheral myelin (BPM). T cell functions of EAN lymph node cells were assessed by measurement of proliferation and by counting of interferon-gamma secreting cells (IFN-gamma sc) in response to the specific antigen BPM and the T cell mitogen phytohemagglutinin (PHA). BRL 38227 and diazoxide at concentrations of 10(-5)M-10(-6)M and pinacidil at concentrations of 10(-5)M-10(-7)M enhanced the proliferative response to both BPM and PHA. The number of IFN-gamma sc was suppressed by the K+ channel openers in the same concentration range. There was a tendency of stronger suppression of cultures with high numbers of BPM-reactive IFN-gamma sc than of cultures with low numbers of BPM-reactive IFN-gamma sc. The applied K+ channel openers are primarily acting on ATP-sensitive K+ channels, which have not been found in T cells so far. The drugs may, therefore, exert non-selective effects on conventional voltage- and/or Ca(++)-dependent channels of T cells. A first trial with in vivo administration of 2.5 mg/kg x day of the drugs resulted in more severe neurological deficits in the early phase of EAN with BRL 38227, whereas pinacidil and diazoxide had no significant effects.

A disturbance of interferon synthesis with the hyperproduction of unusual kinds of interferon can trigger autoimmune disease and play a pathogenetic role in AIDS: the removal of these interferons can be therapeutic

Disturbances of interferon synthesis with the hyperproduction of unusual kinds of interferons may be the initial step which triggers autoimmune disease through a chain of pathological reactions including the disturbances of several immunological and cytokine cascades. Prolonged circulation of this interferon may be a predictive marker of an autoimmune condition; the administration of interferons to animals or humans with autoimmune disease or an underlying or latent autoimmune condition can exacerbate or trigger the disease. Healthy people do not have interferon in their blood. This fundamental disturbance of interferon synthesis can result either from a genetic predisposition or from the influence of certain viruses (or viral particles) or both factors together. AIDS has many features similar to autoimmune disease, including the hyperproduction of aberrant interferon, a type with restricted anti-HIV activity, protectively induced by HIV to allow its continued replication and survival. This interferon stimulates the production of certain cytokines and autoantibodies which help unleash the potentially self-destructive powers of the immune system, bringing immunological chaos. In other words, while usual viruses induce normal interferon, which protects the cells against viral infection, HIV induces an abnormal, defective kind of interferon which ensures virus survival. Since there is no known effective method of destroying HIV directly, removing links in this chain of reactions could indirectly destroy HIV and possibly help restore immune functioning.(ABSTRACT TRUNCATED AT 250 WORDS)

A disturbance of interferon synthesis with the hyperproduction of unusual kinds of interferon can trigger autoimmune disease and play a pathogenetic role in AIDS: the removal of these interferons can be therapeutic

Disturbances of interferon synthesis with the hyperproduction of unusual kinds of interferons may be the initial step which triggers autoimmune disease through a concatenation of pathological reactions including the disturbance of several immunological and interferon cascades. This fundamental disturbance can result either from a genetic predisposition or from the influence of certain viruses (or viral particles) or both factors together. The administration of interferons to individuals with an underlying or latent autoimmune condition can exacerbate or trigger the disease. AIDS has many features similar to autoimmune disease, including the hyperproduction of aberrant interferon, a type with little or no anti-HIV activity, protectively induced by HIV to allow its continued replication and survival. In other words, while most viruses induce normal IFN which protects the cells against viral infection, HIV induces an abnormal, defective kind of IFN which insures viral survival. The neutralization of hyperproduced interferons by polyclonal or monoclonal antibody produced in mouse, or preferably, human hybridoma, removal via extracorporeal means, or the use of antagonists which diminish the production or biological activity of these interferons can be a therapeutic approach to the management of these chronic diseases. In addition, the extracorporeal removal of different kinds of interferons, autoantibodies, autoantigens and other substances from the organism in certain pathological conditions may be an effective and safe method of treatment for autoimmune diseases and AIDS.

Autoreactive T and B cell responses to myelin antigens after diagnostic sural nerve biopsy

To study whether nervous tissue trauma provokes myelin antigen autoreactive T and B cell responses in humans we examined consecutive blood samples from 7 patients with polyneuropathy undergoing diagnostic sural nerve biopsy and 8 control patients undergoing other types of minor surgery. The antigen-specific T cells were assessed by enumerating cells secreting interferon-gamma (IFN-gamma) in response to the myelin components P0, P2, myelin basic protein (MBP) and myelin associated glycoprotein (MAG), and to 4 selected MBP peptides. B cell mediated immunity was assessed by counting numbers of cells secreting antibodies directed against the myelin proteins. On day 7 after biopsy, there were 3-10-fold increased numbers of T and B cells reactive with P0, P2, MBP and MAG in blood of polyneuropathy patients compared to controls, while levels of cells recognizing purified protein derivate or responding to phytohemagglutinin (PHA) did not differ significantly. Comparison of prebiopsy levels on day 0 with post-biopsy levels on day 7 in the polyneuropathy patients revealed a significant increase in T cells recognizing P0, P2 and MAG, and in B cells secreting IgG antibodies against P0 and P2. On day 14 after nerve biopsy these differences were no longer seen. We suggest that in patients with polyneuropathy, sural nerve biopsy with the ensuing wallerian degeneration and myelin breakdown causes transiently increased levels of circulating myelin autoreactive T and B cells. It remains to be determined if this has a physiological role in nerve trauma responses and/or affects the clinicopathological course of the peripheral neuropathy.

Inflammatory mediators in demyelinating disorders of the CNS and PNS

Work in both experimental models and human disorders of the central and peripheral nervous system has delineated multiple effector mechanisms that operate to produce inflammatory demyelination. The role of various soluble inflammatory mediators generated and released by both blood-borne and resident cells in this process will be reviewed. Cytokines such as interleukin (IL)-1, interferon (IFN)-gamma, and tumor necrosis factor (TNF)-alpha are pivotal in orchestrating immune and inflammatory cell-cell interactions and represent potentially noxious molecules to the myelin sheath, Schwann cells, and/or oligodendrocytes. Arachidonic acid metabolites, synthesized by and liberated from astrocytes, microglial cells and macrophages, are intimately involved in the inflammatory process by enhancing vascular permeability, providing chemotactic signals and modulating inflammatory cell activities. Reactive oxygen species can damage myelin by lipid peroxidation and may be cytotoxic to myelin-producing cells. They are released from macrophages and microglial cells in response to inflammatory cytokines. Activation of complement yields a number of inflammatory mediators and results in the assembly of the membrane attack complex that inserts into the myelin sheath-creating pores. Activated complement may contribute both to functional disturbance of neural impulse propagation, and to full-blown demyelination. Proteases, abundantly present at inflammatory foci, can degrade myelin. Vasoactive amines may play an important role in breaching of the blood-brain/blood-nerve barrier. The importance of nitric oxide metabolites in inflammatory demyelination merits investigation. A better understanding of the multiple effector mechanisms operating in inflammatory demyelination may help to devise more efficacious antigen non-specific therapy.

Effects of zimeldine and its metabolites, clomipramine, imipramine and maprotiline in experimental allergic neuritis in Lewis rats

The influence of the selective serotonin (5-HT) reuptake inhibiting antidepressant zimeldine and its metabolite norzimeldine was tested on experimental allergic neuritis (EAN) in Lewis rats, which is an animal model of the Guillain-Barré syndrome (GBS) in man. Zimeldine and norzimeldine both suppressed clinical signs of actively induced EAN when given at a dose of 20 mg/kg/day intraperitoneally via osmotic pumps. The effects of zimeldine, its metabolites norzimeldine and CPP 200 as well as of the antidepressants clomipramine, imipramine and maprotiline on in vitro immune response were tested. Thereby we used an immunospot assay for interferon-gamma (IFN-gamma) produced by lymph node mononuclear cells (MNC), which reflects number of memory T lymphocytes activated by antigen or lectin, in this experiment bovine peripheral nerve myelin (BPM) and phytohemagglutinin (PHA), respectively. In the IFN-gamma secretion assay zimeldine, CPP 200, clomipramine and maprotiline all in a concentration-dependent mode reduced the number of IFN-gamma secreting cells while norzimeldine and imipramine did not affect the IFN-gamma secretion. In assays for proliferation in response to antigen or lectin, the concentration 10(-4) M was judged toxic for all substances tested, and at concentrations below that all but zimeldine showed a dose-dependent slight reduction of MNC proliferation. The action of several drugs on induced T cell secretion of IFN-gamma suggests that the mechanisms for the suppressive effect of zimeldine and norzimeldine on EAN symptoms can be due to an action on myelin T cell autoreactivity. All the monoamine reuptake inhibiting antidepressants tested in this study showed immunomodulatory effects by either a reduction of the number of IFN-gamma-secreting cells or the MNC proliferation. These observations call for further studies of immunological mechanisms in the pathogenesis of mental disorders as well as on the potential role of drugs acting on the monoamine systems in the treatment of recognized autoimmune diseases.

Effect of anti-interferon-gamma and anti-interleukin-2 monoclonal antibody treatment on the development of actively and passively induced experimental allergic encephalomyelitis in the SJL/J mouse

SJL/J mice challenged with myelin basic protein (MBP) in complete Freund's adjuvant (CFA) developed only mild chronic-relapsing experimental allergic encephalomyelitis (EAE) with very low incidence. However, treatment of challenged mice with anti-interferon-gamma (IFN-gamma) monoclonal antibody (mAb) determined severe disease in all cases. Similarly, in passive EAE, the addition of anti-IFN-gamma to the in vitro MBP-activated cells at the time of transfer led to significant disease exacerbation in all recipients. The disease enhancing effect was observed only when the mAb was given at the time of active challenge or of passive transfer, but not at later times. Anti-interleukin-2 (IL-2) antibody had only a marginal effect in the active induction, but drastically reduced the manifestations of passive EAE, even when mixed with a disease-enhancing dose of anti-IFN-gamma. These findings support the notion that IL-2 is required for disease induction whereas IFN-gamma plays a disease-limiting role early in the development of EAE.

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.

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.

The role of complement in myelin phagocytosis during PNS wallerian degeneration

Myelin removal in nerves undergoing wallerian degeneration mainly depends on invading, non-resident macrophages. The present study clarifies the role of serum complement components in this process in vitro and in vivo. Macrophages cocultured with degenerating nerves in vitro were unable to invade these nerves in the presence of C3-deficient serum. Application of C3-deficient serum subsequent to cellular invasion abolished the myelin phagocytic capacity of the invaded macrophages. This indicates that opsonization of myelin by complement components is necessary in myelin ingestion via macrophage receptors. In vivo, a monoclonal antibody to the macrophage complement receptor type 3 (CR3) significantly reduced myelin phagocytosis. Immunohistochemistry with anti-C3 antibodies showed a marked reaction in degenerating nerves. Immunoelectron microscopy localized C3 particles at the degenerating myelin sheaths. Haematogenous cells, invading the degenerating nerves, also showed a strong reaction for C3 in their cytoplasm. These results indicate that complement components play a critical role both in macrophage invasion of degenerating nerves and in the ingestion of myelin by these cells.

T cell immunity and interferon-gamma secretion during experimental allergic encephalomyelitis in Lewis rats

An immunospot assay that detects single secretory cells was used to enumerate interferon-gamma secreting cells (IFN-gamma-sc) in mononuclear cell suspensions from the central nervous system (CNS) and peripheral lymphoid organs after actively induced experimental allergic encephalomyelitis (EAE) in Lewis rats. In the CNS compartment there was a significant increase in the number of IFN-gamma-sc preceding the onset of the clinical signs of EAE. Both in rats with EAE and rats immunized with Freund's complete adjuvant (FCA) the number of IFN-gamma-sc increased in peripheral lymphoid organs, as compared to non-immunized controls. In view of the potent immunoregulatory effects of IFN-gamma, its intra-CNS secretion may play a crucial role for clinicopathological events in EAE. To study the numbers of primed T cells that in response to myelin antigens produced IFN-gamma, mononuclear cell suspensions from peripheral lymphoid organs were precultured to allow for antigen uptake, presentation and T cell triggering, followed by enumeration of IFN-gamma-sc. T cells responding to a peptide of myelin basic protein (MBP) that previously have been shown encephalitogenic in Lewis rats, appeared initially and were quantitatively dominant over the course of EAE. Later, T cell reactivities to multiple regions of MBP appeared, showing that the concept of immunodominance in EAE is non-absolute and time dependent. Splenocyte cultures from EAE rats exposed to the different antigens showed a reduced number of IFN-gamma-sc compared to cultures not exposed to antigen, suggesting an antigen-induced suppression of T cell effector molecules.

Gamma interferon-like immunoreactive material in rat neurons: evidence against a close relationship to gamma interferon

Gamma interferon is a potent immunoregulatory peptide produced by activated lymphocytes. Recently, a gamma interferon-like immunoreactive molecule has been demonstrated immunohistochemically in subpopulations of rat neurons. We have now further characterized this molecule. Western blot analysis of spinal ganglia homogenates revealed a single 60,000 mol. wt band that was immunoreactive with monoclonal antibody DB1 directed against rat gamma interferon. A polyclonal antiserum and the monoclonal antibodies DB10 and DB12 failed to detect this band although all antibodies were able to label the major 18,000 mol. wt band of recombinant gamma interferon on the same blots. The 60,000 mol. wt band was selectively present in homogenates from primary sensory and sympathetic ganglia but was absent from the central nervous system and other peripheral organs, corresponding to the reported immunocytochemical distribution of gamma interferon-like immunoreactivity. The 60,000 mol. wt protein does not appear to be glycosylated. It could not be solubilized by detergents such as Triton X-100 and it co-purified with cytoskeleton-enriched preparations. At the nucleic acid level, Northern blot analysis using probes specific for rat gamma interferon mRNA failed to detect specific mRNA in rat spinal ganglia, whereas a strong 1.2 kb signal was detected in activated spleen cells. Functionally, gamma interferon-like immunoreactive material is strongly induced in superior cervical ganglion neurons after preganglionic axotomy of the sympathetic chain, but remains constant or slightly decreases in L5 spinal ganglion neurons after sciatic nerve transection. In contrast, major histocompatibility complex antigens are strongly induced on non-neuronal cells in both systems. We conclude that the neuronal gamma interferon-like immunoreactive material is clearly distinct from lymphocyte-derived gamma interferon and might not be involved in the control of major histocompatibility complex expression on glial cells.