ENCEPHALITOGEN-INDUCED INHIBITION OF EXPERIMENTAL ALLERGIC ENCEPHALOMYELITIS: PREVENTION, SUPPRESSION AND THERAPY

Ingested (oral) adrenocorticotropic hormone (ACTH) inhibits interleukin-17 in the central nervous system after adoptive transfer of T helper (Th)1/Th17 T cells in the mouse model of multiple sclerosis, experimental autoimmune encephalomyelitis

BACKGROUND

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory autoimmune disease of the central nervous system (CNS) that resembles multiple sclerosis (MS) and provides a useful animal model for the evaluation of mechanisms of action for potential immunomodulatory therapies. We have previously shown that oral adrenocorticotropic hormone (ACTH) decreased either interleukin (IL)-17 and/or interferon (IFN)γ in the CNS during EAE.

OBJECTIVE

We wanted to examine whether oral ACTH showed a preferential effect on Th17 as opposed to Th1 phenotypes.

DESIGN/METHODS

We therefore examined whether oral ACTH could inhibit EAE in the C57BL/6 (B6) mouse strain after adoptive transfer of equal quantities of Th17 (CD4+IL-17+) and Th1 (CD4+IFN-γ+) T cells generated after in vitro skewing. B6 mice were injected with a 1:1 ratio of Th1:Th17 T cells and were gavaged daily with control scrambled peptide (s-MSH) or 10 μg ACTH.

RESULTS

Ingested (oral) ACTH attenuated ongoing clinical EAE disease and decreased the frequencies of Th17 cells in the spleen and in the CNS, but not Th1.

CONCLUSIONS

These findings suggest that there was preferential regulation of Th17 cells by oral ACTH compared to Th1 T cells in the CNS.

Ingested ACTH blocks Th17 production by inhibiting GALT IL-6

BACKGROUND

EAE is an inflammatory autoimmune process of the CNS that resembles multiple sclerosis (MS) and provides a useful animal model for the evaluation of mechanisms of action for potential immunomodulatory therapies. Oral ACTH (adrenocorticotropic hormone) can decrease clinical disease, IL-17 and Th1-like encephalitogenic IFN-γ secretion and increase Treg frequency. The mechanism by which oral ACTH decreases inflammatory proteins and increases Treg cell frequencies is unknown.

OBJECTIVE

IL-6 is a pivotal cytokine in the gut that determines the relative frequencies of Th17 vs Treg cells. We examined whether oral ACTH inhibited IL-6 in the gut associated lymphoid tissue (GALT) in EAE.

DESIGN/METHODS

B6 mice were immunized with MOG peptide 35-55 and gavaged with scrambled ACTH (scrambled melanocyte stimulating hormone [scrambled α-MSH]) or ACTH 1-39 during ongoing disease.

RESULTS

Ingested (oral) ACTH inhibited ongoing clinical disease. In the lamina propria (LP) immune compartment, there were significantly less CD11b + IL-6 and IL-17 producing lymphocytes from ACTH fed mice compared to s-MSH fed mice. There was also a decrease in the frequency of IL-17 and IFN-γ producing spleen cells and an increase in CD4 + FoxP3+ Treg cell frequency in ACTH fed mice compared to s-MSH fed control spleens. There were less IFN-γ producing CNS lymphocytes in ACTH fed mice compared to s-MSH fed control CNS.

CONCLUSIONS

Ingested ACTH inhibits EAE clinical disease by inhibiting IL-6 in the GALT.

Ingested (oral) anti-IL-12/23 inhibits EAE

BACKGROUND

Blocking the activity of IL-12/23 can inhibit autoimmune diseases such as psoriasis.

OBJECTIVE

We examined whether an antibody against IL-12/23, ustekinumab (UTZ) (Stelera®), used clinically in psoriasis would have similar anti-inflammatory effects in EAE after oral administration.

DESIGN/METHODS

B6 mice were immunized with MOG peptide 35-55 and gavaged with isotype IgG control or UTZ during ongoing disease. Splenocytes, CD4(+) T cells or macrophages/monocyte lineage cells (CD11b(+)) from control fed or UTZ fed mice were adoptively transferred into active MOG peptide 35-55 immunized recipient mice during ongoing disease. Actively fed and recipient mice were examined for disease inhibition, inflammation, and cytokine responses.

RESULTS

Ingested (oral) UTZ inhibited ongoing disease and decreased inflammation. Adoptively transferred cells from UTZ fed donors protected against actively induced disease and decreased inflammation. Oral UTZ decreased pro-inflammatory cytokines Th1-like cytokines IL-2, IL-12, IFN-γ, IL-17 (Teff) and TNF-α in UTZ fed mice and increased counter-regulatory cytokines IL-4, IL-10 and IL-13 in recipients of donor cells from UTZ fed mice.

CONCLUSIONS

Ingested (orally administered) UTZ can inhibit disease, CNS inflammation, decrease pro-inflammatory Th1-like and Th17 cytokines and increase Th2-like anti-inflammatory cytokines.

Ingested (oral) tocilizumab inhibits EAE

BACKGROUND

Blocking the activity of IL-6 can inhibit autoimmune diseases such as rheumatoid arthritis and Crohn's disease.

OBJECTIVE

We examined whether an antibody against IL-6, tocilizumab (TCZ) (Actemra®), used clinically in rheumatoid arthritis (RA) would have similar anti-inflammatory effects in EAE after oral administration.

DESIGN/METHOD

B6 mice were immunized with MOG peptide 35-55 and gavaged with control saline or TCZ during ongoing disease. Splenocytes, CD4(+) T cells or macrophages/monocyte lineage cells (CD11b(+)) from control fed or TCZ fed mice were adoptively transferred into active MOG peptide 35-55 immunized recipient mice during ongoing disease. Actively fed and recipient mice were examined for disease inhibition, inflammation, and cytokine responses.

RESULTS

Ingested (oral) TCZ inhibited ongoing disease and decreased inflammation. Adoptively transferred cells from TCZ fed donors protected against actively induced disease and decreased inflammation. There was a decrease in IL-6 in actively treated spleen, decrease in TNF-α, Th1-like cytokine IL-12 and increase in Th2-like cytokine IL-10 in active fed and adoptively treated recipients.

CONCLUSIONS

Ingested (orally administered) TCZ can inhibit disease, CNS inflammation, decrease pro-inflammatory Th1-like cytokines and increase Th2-like anti-inflammatory cytokines.

Ingested (oral) thyrotropin releasing factor (TRH) inhibits EAE

BACKGROUND

Ingested immunoactive proteins type I IFN, SIRS peptide 1-21, α-MSH, ACTH, SST inhibit clinical attacks and inflammation in acute EAE by decreasing Th1-like cytokines, increasing Th2-like cytokines or increasing T(reg) cell frequencies.

OBJECTIVE

We examined whether another protein, thyrotropin releasing factor (TRH), would have similar anti-inflammatory effects in EAE after oral administration.

DESIGN/METHODS

B6 mice were immunized with MOG peptide 35-55 and gavaged with control saline or TRH during ongoing disease. Splenocytes from mock fed or TRH fed mice were adoptively transferred into active MOG peptide 35-55 immunized recipient mice during ongoing disease.

RESULTS

Ingested (oral) TRH inhibited ongoing disease and decreased inflammation. Adoptively transferred cells from TRH fed donors protected against actively induced disease and decreased inflammation. In actively fed mice, oral TRH decreased IL-17 and TNF-α cytokines in both the spleen and the CNS. In recipients of donor cells from TRH fed mice there was a reduction of Th1 and Th17 and induction of Th2-like IL-13 cytokines in both the spleen and CNS. Oral TRH decreased clinical score and decreased inflammatory foci in both actively fed and recipients of actively fed mice. There was no significant increase in T(reg) cell frequencies in actively fed or recipients of TRH fed donor cells.

CONCLUSIONS

Ingested (orally administered) TRH can inhibit clinical disease, inhibit CNS inflammation by decreasing Th1-like, Th17 and TNF-α cytokines and increasing Th2-like cytokines (IL-13) in the CNS.

Ingested (oral) neuropeptide Y inhibits EAE

BACKGROUND

Ingested immunoactive proteins, type I IFN, SIRS peptide 1-21, α-MSH, ACTH, and SST inhibit clinical attacks and inflammation in acute EAE by decreasing Th1-like cytokines, increasing Th2-like cytokines or increasing T(reg) cell frequencies.

OBJECTIVE

We examined whether another protein, neuropeptide Y, would have similar anti-inflammatory effects in EAE after oral administration.

DESIGN/METHODS

B6 mice were immunized with MOG peptide 35-55 and gavaged with control saline or NPY during ongoing disease. Splenocytes from mock fed or NPY fed mice were adoptively transferred into active MOG peptide 35-55 immunized recipient mice during ongoing disease.

RESULTS

Ingested (oral) NPY inhibited ongoing disease, and decreased inflammation. Adoptively transferred cells from NPY fed donors protected against actively induced disease and decreased inflammation. In actively fed mice, oral NPY decreased Th1-like cytokines and increased Th2-like IL-13 cytokines in both the spleen and the CNS. In recipients of donor cells from NPY fed mice there was a reduction of Th1 and Th17 and induction of Th2-like IL-13 cytokines in both the spleen and CNS. Oral NPY decreased clinical score and decreased inflammatory foci in both actively fed and recipients of actively fed mice. There was no significant increase in T(reg) cell frequencies in actively fed or recipients of NPY fed donor cells.

CONCLUSIONS

Ingested (orally administered) NPY can inhibit clinical disease, inhibit CNS inflammation by decreasing Th17 and Th1-like cytokines and increasing Th2-like cytokines in the CNS.

Ingested (oral) ACTH inhibits EAE

Ingested type I IFN and SIRS peptide inhibit EAE. We examined whether another immunoactive protein, ACTH, would have similar anti-inflammatory effects in EAE after oral administration. B6 mice were immunized and gavaged with control saline or ACTH starting on the onset of disease. ACTH decreased clinical score and decreased inflammatory foci. CNS lymphocytes showed decreases in IL-17 (T(eff)) and Th1-like encephalitogenic cytokines IL-2 and IFN-γ in the ACTH fed group compared to the mock fed group. Adoptive transfer of ACTH fed splenocytes into MOG immunized recipient mice with early clinical disease suppressed disease severity compared to splenocytes from mock fed donors. The protected recipients showed decreased splenic IL-17 (T(eff)) and Th1-like cytokine IFN-γ and increased CNS secretion of immunoregulatory IL-4 and chemokine M-CSF. Splenic CD4+CD25+ FoxP3+ frequency doubled in ACTH fed compared to control fed mice. Increased immuno-regulatory IL-4 and M-CSF secreting cell populations is the mechanism of protection in adoptively protected recipients and reflects the direct action of ACTH on the immune system.

Ingested (oral) SIRS peptide 1–21 inhibits acute EAE by inducing Th2-like cytokines

OBJECTIVE

Ingested type I IFN inhibits clinical attacks, relapses and inflammation in murine chronic relapsing EAE by inhibiting Th1-like cytokines. Type I IFN activates human suppressor T cells that produce SIRS.

METHODS

We examined whether oral (ingested) SIRS peptide inhibits EAE by decreasing Th1-like cytokines.

RESULTS

Parenteral SIRS peptide 1-21 showed a significant inhibition of disease severity in murine EAE. Ingested SIRS peptide at 10 and 100 microg SIRS peptide showed a significant inhibition of disease severity but also a prolonged delay in the onset of disease compared to placebo. There were significantly less inflammatory foci in the SIRS peptide fed group compared to the control mock fed group. Splenocytes from SIRS peptide 1-21 fed mice showed increased production of Th2-like CD30L, IL-13, TCA-3 cytokines/chemokines and decreased production of Th1-like cytokine lymphotactin.

INTERPRETATION

Ingested (oral) SIRS peptide significantly inhibits both clinical EAE and inflammation predominately via counter-regulatory type 2-like cytokines/chemokines IL-13, CD30L and TCA-3.

Monomeric DR2/MOG-35-55 recombinant TCR ligand treats relapses of experimental encephalomyelitis in DR2 transgenic mice

Treatment of human autoimmune diseases such as multiple sclerosis (MS) will likely require agents that can prevent or reverse the inflammatory process that results in clinical relapses and disease progression. We evaluated the ability of a newly designed monomeric recombinant TCR ligand (RTL342M) containing HLA-DR2 peptide-binding domains covalently linked to MOG-35-55 peptide to prevent and treat both the initial episode and subsequent relapses of experimental autoimmune encephalomyelitis (EAE) in HLA-DR2 transgenic mice. Single doses of RTL342M given either i.v. or s.c. to HLA-DR2 mice produced a rapid (within 24 h) and dose-dependent reversal of clinical signs of paralytic EAE, and even a single dose < or = 2 microg could produce a significant treatment effect. Multiple daily doses were even more effective than the same total amount of RTL given as a single dose. By establishing the minimal effective dose, we determined that RTLs may be 50 times more potent than molar equivalent doses of myelin peptide alone. RTL342M given prior to induction of EAE prevented disease in most mice, and the remainder could be successfully retreated with RTL. Most important for clinical application, RTL342M was highly effective for treating EAE relapses when given periodically prior to the relapse or even after relapses had occurred. These data demonstrate the rapid and potent clinical effects of RTL342M at disease onset and during relapses in EAE and establish important principles governing the application of this novel approach as a possible therapy for patients with MS.

Abnormal hormonal control of gut hydrolytic enzymes causes autoimmune attack on the CNS by production of immune-mimic and adjuvant molecules: A comprehensive explanation for the induction of multiple sclerosis

Multiple sclerosis (MS) is generally thought to be caused by an autoimmune attack on central nervous system (CNS) myelin. A microorganism containing a mimic of an immunogenic region of a myelin protein initiates the autoimmune process. However, no specific "MS" microorganism has been found. Recently a large number of normal human gut bacteria were found to possess different encephalitogenic mimics. A hypothesis is presented that the autoimmune process is started by abnormal proteolytic digestion of these bacteria. Sufficient quantities of the mimics are produced to be recognized by the immune system. Since proteolytic processes in the gut are strictly controlled, it is proposed that the MS process is triggered by abnormal hormonal control of gut proteolytic enzymes. It has previously been suggested that the recognition of CNS myelin antigens by activated MS immune cells is facilitated by proteolytic processing of myelin proteins. The CNS proteases are also under rigid control and these control processes are the same as is in the gut. Therefore, MS clinical activity is the result of improper hydrolytic degradation in the brain-gut axis caused by an abnormal hormonal variation.

Antigen-specific therapies in multiple sclerosis: going beyond proteins and peptides

Multiple sclerosis (MS) is a complex immune-mediated disease resulting largely from an autoimmune attack against components of central nervous system myelin, including several proteins and lipids. Knowledge about the details of this anomalous immune response has come mostly from studies in the animal model experimental autoimmune encephalomyelitis (EAE). In this model, it has been possible to prevent and effectively treat established disease through several antigen-specific therapeutic strategies, which have included administration of whole myelin or myelin proteins by various routes, random copolymers consisting of the main major histocompatability complex (MHC) and T-cell receptor (TCR) contact amino acid residues, altered peptide ligands of dominant myelin epitopes in which one or more residues are selectively substituted, and lately DNA vaccination encoding self-myelin antigens. However, there have been difficulties in making successful transitions from animal models to human clinical trials, due either to lack of efficacy or unforeseen complications. Despite these problems, antigen-specific therapies have retained their attraction for clinicians and scientists alike, and hopefully the upcoming generation of agents--including altered peptide ligands and DNA vaccines--will benefit from the increasing knowledge about this disease and surmount existing difficulties to make an impact in the treatment of multiple sclerosis.

Histo-clinical variation in multiple sclerosis: Heterogeneous proteolytic immunogenic processing

Multiple sclerosis (MS) presents an incredible histo-clinical variation. It consists of an unpredictable series of relapses, remissions and stationary phases. The initial symptoms vary considerably. Any hypothesis of the pathology of MS must include an explanation of this oddity. Current theory suggests that MS is a collection of diseases which produce generally the same result. However, this is not a satisfactory explanation. MS appears as an enormous continuum of disease paths rather than a finite group of well-defined courses. A hypothesis is presented that histo-clinical variation in MS is due to variable proteolytic processing of several potential immunogens. MS is generally thought to be caused by an autoimmune attack on myelin components. Several myelin proteins, myelin basic protein, lipoprotein, oligodendrocyte related glycoprotein and oligodendrocyte basic protein, are encephalitogenic. Within these proteins are short sequences, which themselves are encephalitogenic. In order for potential immunogens to be "seen" by the immune system they first must be processed. This processing is performed by intracellular and extracellular proteases. A large number of different proteases are located throughout the central nervous system. Their concentrations vary with location and time. Most are under strict control. While myelin has a consistent structure, the action of proteases can present variable concentrations of immunogenic peptides. Because of the differences in location, concentration and control of the central nervous system's (CNS) proteases, the same potential immunogen could be presented to the immune system in different locations within the CNS at different times. At a given time and location, the immune system may be presented with no potential immunogens, one potential immunogen or possibly many immunogens. Therefore, because of the dynamic characteristic of presentation, one would expect to see the initial MS symptoms to be variable. This variability would be continued with subsequent symptoms. This is what is seen in multiple sclerosis. A procedure for testing this hypothesis is presented.

Induction of experimental autoimmune encephalomyelitis in Dark Agouti rats without adjuvant

Experimental autoimmune encephalomyelitis (EAE) is a well-recognized model for multiple sclerosis (MS) in humans. However, adjuvants used with encephalitogens to induce EAE produce non-specific effects interfering with the mechanisms involved in the autoimmune response to the central nervous system (CNS) tissue. It is therefore important to establish a more suitable model of EAE for analysis of autoimmune phenomena resembling those operative in MS. Here we report that EAE can be induced regularly in Dark Agouti (DA) strain of rats with spinal cord tissue without any adjuvant, as judged by both clinical and histological parameters. The incidence and severity of EAE depended on the origin of the encephalitogen, the rat versus guinea pig spinal cord homogenate being more efficient. Furthermore, EAE could be reinduced in animals which had recovered from disease that had been induced actively with encephalitogen alone, suggesting the role of adjuvant-generated non-specific mechanisms in resistance to reinduction of EAE. Thus, EAE induced in DA rats with encephalitogen alone provides a reproducible model for defining pathogenically relevant events in CNS autoimmunity devoid of the potentially misleading effects of adjuvants.

Vaccination stimulates retinal ganglion cell regeneration in the adult optic nerve

We examined whether vaccination of adult rats with spinal cord homogenate (SCH) can promote regeneration of retinal ganglion cells (RGCs) after microcrush lesion of the optic nerve. Injured animals vaccinated with SCH showed axon growth into the optic nerve and such regeneration was not observed in animals vaccinated with liver homogenate (LH). Regeneration was not a consequence of neuroprotection since our vaccine did not protect RGCs from axotomy-induced cell death. Sera of vaccinated animals were tested for antibodies against myelin-associated glycoprotein, NogoA, Nogo-66 receptor, or chondroitin sulphate proteoglycans (CSPG), but no significant levels were detected. Antibodies to myelin basic protein were present in the serum of some SCH-vaccinated animals. In culture, serum from SCH-vaccinated animals promoted RGC growth on myelin but not on CSPG. Our results show that the effect of the pro-regenerative vaccine is mediated by antibodies to SCH. However, we were not able to detect a significant immune reaction to growth inhibitory proteins, suggesting alternative mechanisms for the success of vaccination to promote regeneration.

Rag-1-dependent cells are necessary for 1,25-dihydroxyvitamin D(3) prevention of experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is a demyelinating disease involving genetic and environmental risk factors. Geographic, genetic, and biological evidence suggests that one environmental risk factor may be lack of vitamin D. Here, we investigated how 1,25-dihydroxyvitamin D(3) (1,25-(OH)(2)D(3)) inhibits experimental autoimmune encephalomyelitis (EAE), an MS model. The experiments used adoptive transfer of TCR-transgenic (TCR1) cells specific for myelin basic protein (MBP) peptide into unprimed recipients. When unprimed TCR1 splenocytes were transferred, and the recipients were immunized with peptide, the mock-treated mice developed EAE, but the 1,25-(OH)(2)D(3)-treated recipients remained disease-free. Both groups had TCR1 T cells that proliferated in response to MBP Ac1-11 and produced IFN-gamma but not IL-4 in the lymph node. In the central nervous system (CNS), the mock-treated mice had activated TCR1 T cells that produced IFN-gamma but not IL-4, while the 1,25-(OH)(2)D(3)-treated mice had TCR1 T cells with a non-activated phenotype that did not produce IFN-gamma or IL-4. When activated TCR1 T cells producing IFN-gamma were transferred into unprimed mice, the mock-treated and the 1,25-(OH)(2)D(3)-treated recipients developed EAE. Likewise, the 1,25-(OH)(2)D(3) did not inhibit Th1 cell IFN-gamma production or promote Th2 cell genesis or IL-4 production in vitro. Finally, the 1,25-(OH)(2)D(3) inhibited EAE in MBP-specific TCR-transgenic mice that were Rag-1(+), but not in animals that were Rag-1-null. Together, these data refute the hypothesis that the hormone inhibits Th1 cell genesis or function directly or through an action on antigen-presenting cells, or promotes Th2 cell genesis or function. Instead, the evidence supports a model wherein the 1,25-(OH)(2)D(3) acts through a Rag-1-dependent cell to limit the occurrence of activated, autoreactive T cells in the CNS.

Adoptive transfer from interferon-alpha-fed mice is associated with inhibition of active experimental autoimmune encephalomyelitis by decreasing recipient tumor necrosis factor-alpha secretion

Ingested type I interferon (IFN) suppresses clinical relapse in murine chronic experimental autoimmune encephalomyelitis (EAE), inhibits clinical attacks more effectively than subcutaneous doses, and decreases the adoptive transfer of EAE. To determine whether splenocytes from IFN-fed donors were "suppressor-like" populations, donor SJL/J mice were immunized and fed with mock IFN-alpha or with IFN-alpha every other day for at least 4 weeks after initial clinical attack. Recipients of adoptively transferred CD8+ T cells from mock IFN-alpha-fed donors showed no clinical improvement of clinical disease compared with actively immunized controls. In contrast, recipients of adoptively transferred CD8+ T cells from IFN-alpha-fed donors showed decreased clinical disease compared with recipients of mock IFN-alpha-fed CD8+ T cells. To evaluate the mechanism of protection by donor CD8+ T cells and to determine if ingested IFN-alpha activates natural immunomodulatory cell populations, the authors used the acute EAE model and naïve-fed donor animals as sources of T cells and CD8+ T cells. Con A-activated spleen T cells from naïve nonimmunized mock IFN-alpha-fed donors inhibited actively induced disease and showed decreased recipient TNF-alpha secretion compared with recipients of T cells from mock IFN-fed mice. Donor activated spleen CD8+ T cells from naïve nonimmunized IFN-alpha-fed animals suppressed actively induced EAE in recipients and showed decreased IFN-gamma and TNF-alpha proinflammatory secretion. Decreased recipient TNF-alpha secretion correlates best with the disease protection from IFN-fed T and CD8+ T cells.

Suppressor cells in demyelinating disease: a new paradigm for the new millennium

This brief review highlights investigations conducted over the past three decades concerning the role of suppressor T cells in the regulation of experimental autoimmune encephalomyelitis (EAE). In addition, more recent studies are summarized which suggest that apoptosis of autoreactive T cells is also involved in the regulation of EAE. The possibility that natural killer (NK) cells mediate apoptosis is also considered.

Strain Variation in Autoimmunity: Attempted Tolerization of DA Rats Results in the Induction of Experimental Autoimmune Encephalomyelitis

This paper reports that DA rats develop experimental autoimmune encephalomyelitis (EAE) when immunized with encephalitogenic myelin basic protein (MBP) peptide (MBP63–81) in IFA. In contrast, most rodent strains are tolerized by this procedure. Doses as low as 5 μg peptide + IFA induced EAE in DA rats. Lewis (LEW) rats did not develop EAE, even after immunization with 100 μg encephalitogenic peptide (MBP68–86) + IFA, but were rendered tolerant to EAE. DA rat T cells proliferated to peptide, and proliferation was inhibited by CTLA4Ig, and by anti-B7.1 and anti-B7.2 mAbs. This indicates that the ease of induction of EAE in this strain does not reflect a decreased requirement for T cell costimulation through the B7/CD28 costimulatory pathway. The inhibitory effect of CTLA4Ig was abrogated in the presence of anti-TGF-β-neutralizing Ab. An encephalitogenic DA T cell line expressed mRNA for the Th1 cytokines IFN-γ and TNF-α, as well as IL-10, and secreted these cytokines. In contrast, a T cell line from peptide + IFA-immunized LEW rats (which did not develop EAE) failed to secrete these cytokines. Although this line did not express TNF-α or IL-10 mRNA, IFN-γ mRNA was detected, suggesting posttranscriptional regulation of IFN-γ expression. Attempts to induce unresponsiveness in DA rats with encephalitogenic peptide-coupled splenocytes were also unsuccessful.

Sequence determinants of modified cobra venom neurotoxin which induce immune resistance to experimental allergic encephalomyelitis: molecular mechanisms for immunologic action

A nontoxic, iodoacetamide-modified cobratoxin derivative (CAM-NTX) induced resistance to experimental allergic encephalomyelitis (EAE) in guinea pigs. Resistance was retained after trypsin digestion and shown to reside in N-terminal and central peptides of CAM-NTX. A similarly modified protein cardiotoxin (CAM-CTX), representative of proteins homologous with cobratoxin, was not immunosuppressive. Depressed clinical symptoms in EAE-resistant animals correlated with reduced lymphocytic infiltration of the brain. Antibody to myelin basic protein (MBP) was reduced in immunosuppressed animals. The immunoinhibitory determinants in CAM-NTX may mimic immune response suppressor proteins (SIRS-alpha 7) and the EAE-resistance region of MBP.

Tolerance induction by acylated peptides: effect on encephalitogenic T cell lines

We reported previously that acylation of an encephalitogenic peptide of myelin basic protein (MBP68-86) by attachment of palmitoyl chloride (PAL68-86) converted this peptide into a powerful tolerogen for EAE in the Lewis rat. In this study we show that T cell lines derived from a PAL68-86-protected rat proliferated poorly to MBP68-86 in vitro, even after repeated passages in this peptide and IL-2. Conversely, T cell lines derived from untreated rats that were challenged with MBP68-86 or PAL68-86 in CFA responded vigorously to MBP68-86 when propagated for many passages in this peptide but became gradually unresponsive after being propagated in the presence of PAL68-86. The modulation of the T cell lines by PAL68-86 in vitro was reflected by a significant reduction in their ability to transfer EAE to recipients. A high percentage of cells stained with an anti-Vbeta8.2 antibody, regardless of whether they were propagated in the presence of unmodified or acylated peptide. The results are consistent with the notion that tolerance induced by PAL68-86 operates by functional inactivation and provide the basis for the use of acylated peptides in the antigen-specific treatment of autoimmune diseases.

Soluble antigen therapy induces apoptosis of autoreactive T cells preferentially in the target organ rather than in the peripheral lymphoid organs

The administration of soluble myelin proteins is an effective way of down-regulating the inflammation in the central nervous system (CNS) in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. To shed more light on the mechanism of this antigen-specific therapy, we determined the effect of the intraperitoneal (i.p.) injection of soluble myelin basic protein (MBP) on Tcell apoptosis in the CNS and peripheral lymphoid organs of Lewis rats with EAE induced by inoculation with MBP and complete Freund's adjuvant. In particular we assessed the level of apoptosis of Vbeta8.2+ Tcells, which constitute the predominant encephalitogenic MBP-reactive T cell population in the Lewis rat. The daily i.p. injection of MBP for 3 days from the onset of neurological signs inhibited the further development of neurological signs of EAE. Using two-color flow cytometry we found that a single i.p. injection of MBP increased the level of apoptosis of the Vbeta8.2+ T cell population in the CNS to 26.2% compared to 7.4% in saline-treated rats and 7.6% in ovalbumin-treated rats. In contrast, treatment with MBP did not increase the level of apoptosis of the Vbeta8.2+ population in the popliteal lymph node draining the inoculation site (1.4%) or in the spleen (1.6%) above that occurring in saline-treated rats (1.6% and 1.1%, respectively). Limiting dilution analysis revealed that the frequency of T cells reactive to the major encephalitogenic epitope, MBP72-89, was decreased in the CNS but not in the popliteal lymph node by this treatment. Three-color flow cytometry in MBP-treated rats demonstrated that CNS Vbeta8.2+ T cells expressing Fas (CD95) and Fas ligand were highly vulnerable to apoptosis compared to Vbeta8.2+ Tcells not expressing these proteins. We conclude that the i.p. injection of MBP increases the spontaneously occurring Fas-mediated activation-induced apoptosis of autoreactive T cells in the CNS in EAE and that this contributes to the therapeutic effect of the injection.

Approaches to the treatment of central nervous system autoimmune disease using specific neuroantigen

The ultimate aim in the treatment of autoimmune disease is to restore self-tolerance to the autoantigen(s) in question. In lieu of this ideal result, the conversion of a destructive or pathogenic autoimmune response into one of benign autoimmunity would also be highly desirable. In either case the use of the antigenic epitope, which is the target of the destructive immune response, would ideally be employed so as to give specificity to the protection without the need for long-term immunosuppression. This review describes a number of different approaches using various forms, doses, and routes of injection of specific neuroantigen to inhibit the different clinical varieties of autoimmune encephalomyelitis in a number of animal models; all done with the view to translating the findings into the clinic for the treatment of multiple sclerosis. We conclude that any treatment strategy for multiple sclerosis (MS) must have a number of features: it must be clinically acceptable, specific, long-lasting, require only short-term treatment, able to shunt off ongoing disease, and have the potential to prevent or deal with epitope spreading. Few of the approaches we describe fulfill all of these criteria. We suggest that investigations of new adjunctive agents to be used with a specific antigen be pursued, and that currently the use of chimeric proteins or DNA vaccination with or without the new adjunctives may hold the most hope for the future.

Suppression of experimental allergic encephalomyelitis in the Lewis rat, by administration of an acylated synthetic peptide of myelin basic protein

A Myelin Basic Protein (MBP) epitope encephalitogenic for the Lewis rat (amino acid residues 68-86) was synthesized and acylated by the attachment of a palmitoyl residue. Lewis rats treated intravenously (i.v.) with the palmitoylated peptide alone were better protected against clinical manifestations of experimental allergic encephalomyelitis (EAE) than rats treated with the peptide inserted into liposomes or with the native peptide at similar doses. The administration of the acylated peptide (PAL68 86) conferred excellent protection against a challenge with the encephalitogenic peptide (p68-86) or with the intact MBP molecule, both before and after induction of active disease, and also when administered to recipients after the transfer of lymphocytes from MBP-challenged donors. Histological manifestations were also reduced to a statistically significant degree. Treatment with a palmitoylated peptide from a non-encephalitogenic region of the MBP molecule (PAL44-62) or with a palmitoylated unrelated peptide were ineffective. In vitro Ag-specific proliferative responses as well as the ability to transfer disease to syngeneic recipients, by lymph node lymphocytes from PAL68-86-treated donors, were considerably reduced. Addition of IL-2 to these cultures failed to restore either Ag-specific responsiveness or the ability of the cells to transfer disease. The results suggest that the administration of acylated peptides induces a profound state of unresponsiveness, and thus may provide an effective means for treating T cell-mediated autoimmune inflammatory disorders.

Ingested IFN-alpha has biological effects in humans with relapsing-remitting multiple sclerosis

Parenterally administered human recombinant type I interferons (hrIFN) in relapsing-remitting multiple sclerosis (RRMS) decrease relapses and spontaneous in vitro IFN-gamma production, reduce clinical progression, and decrease magnetic resonance imaging (MRI)-defined disease activity and lesions. Parenterally administered type I IFN use is limited by clinical and chemical toxicities, and the induction of antibodies that abrogate their activity in vivo correlated with the loss of clinical benefit. Therefore, we determined whether ingested IFN-alpha was non-toxic and had biological effects in humans. Ingested hrIFN-alpha showed no toxicity in normal volunteers or patients with RRMS at doses ranging from 300 to 100,000 units. In subjects with RRMS, a significant decrease in Con A-mediated proliferation and serum soluble intercellular adhesion molecule-1 (sICAM-1), a surrogate measure for disease activity in MS, was found after ingesting 10,000 and 30,000 units IFN-alpha The RRMS subjects also showed decreased IL-2 secretion after ingesting 10,000 units IFN-alpha and decreased IFN-gamma, TGF-beta and IL-10 production after ingesting 30,000 units IFN-alpha. The decreased secretion of IFN-gamma and IL-2 by ingested IFN-alpha suggests that oral IFN-alpha may cause a functional inhibition of Th J-like T helper cells in RRMS, a potential site of intervention at the level of effector T cells in MS. Our studies support the oral use of human IFN-alpha as a biological response modifier in humans.

Experimental autoimmune encephalomyelitis: antigen-induced inhibition of biochemical and immunohistological alterations

A comprehensive biochemical, immunological, and histological study was undertaken during suppression of experimental autoimmune encephalomyelitis (EAE) induced by antigen-specific inhibition of the immune response. Pretreatment of Wistar rats by intraperitoneal administration of low doses of saline-soluble bovine myelin or myelin basic protein (MBP) but not with ovalbumin suppresses the appearance of the clinical symptoms of EAE induced by sensitization with bovine myelin in complete Freund's adjuvant. Analysis of the central nervous system (CNS) of animals pretreated with MBP or whole myelin shows inhibition of the diminution of MBP and 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) activity observed in the EAE animals or in rats pretreated with ovalbumin. With respect to the CNS lipid content, these suppressive treatments abolish the increase in esterified cholesterol and partially revert the diminution in the content of cerebrosides and total cholesterol characteristic of the acute stage of the disease. Concomitantly, meningeal and parenchymal infiltration with mononuclear cells and deposits of immunoglobulins in the infiltrated regions as well as in spinal cord motor neurons were reduced. Analysis of the humoral response to myelin antigens shows that all EAE as well as treated animals developed antibodies to MBP and other myelin proteins. However, a higher incidence and level of these antibodies was observed in nontreated EAE animals and MBP- and ovalbumin-treated rats, while rats treated with total bovine myelin showed a highly reduced humoral response. The present results indicate that intraperitoneal treatment with soluble forms of myelin antigens, concomitant with the suppression of the clinical symptoms of the disease, markedly reduces the biochemical and histological alterations occurring in EAE animals and produces changes in the autoimmune humoral response.

Intravenous antigen administration as a therapy for autoimmune demyelinating disease

Experimental allergic encephalomyelitis is a prototypic autoimmune disease characterized by central nervous system inflammation and demyelination. Previously, we demonstrated that intravenous administration of high doses of myelin basic protein abrogated the clinical and pathological signs of experimental allergic encephalomyelitis by causing the deletion of encephalitogenic, CD4+, myelin basic protein-specific T cells through antigen-induced programmed cell death. In the present study, we further characterized the ability of intravenous antigen administration to attenuate an immune response by myelin basic protein-reactive encephalitogenic T cells. We demonstrated that multiple injections of myelin basic protein are required to achieve a therapeutic response, and that this form of therapy is effective even after prolonged chronic disease. These studies showed that although interleukin-2-stimulated cell cycling is an important factor leading to T-cell death, the administration of exogenous interleukin-2 with antigen can result in the aggravation of clinical disease compared to administration of antigen alone. More importantly, administration of myelin basic protein alone without interleukin-2 was sufficient to reduce autoreactive T cells and clinical disease in experimental autoimmune encephalomyelitis. Our experiments support the rationale for antigen-specific therapy aimed at inducing the programmed death of autoreactive T cells in autoimmune diseases, potentially including the human demyelinating disease multiple sclerosis.

Spontaneous and induced remyelination in multiple sclerosis and the Theiler's virus model of central nervous system demyelination

Remyelination in the central nervous system, originally thought to occur rarely, if ever, is now an established phenomena in multiple sclerosis patients. However, the extent of myelin repair is incomplete and limited. Experimental models of central nervous system demyelination provide an opportunity to study the cellular and molecular events involved in remyelination. These models may provide some clue to why remyelination in multiple sclerosis is incomplete as well as suggest potential methods to stimulate central nervous system repair. In this review we examine the morphological aspects of central nervous system remyelination and discuss both spontaneous and induced remyelination in multiple sclerosis and experimental models of central nervous system demyelination. We give special emphasis to the Theiler's virus model of central nervous system demyelination and its usefulness to identify therapeutic agents to promote remyelination. The role of immunoglobulins in promoting remyelination in both the Theiler's model system and in multiple sclerosis is discussed. Finally, we examine the potential physiological role of demyelination and remyelination and its relationship with clinical manifestations of central nervous system disease.

Modification of acute experimental autoimmune encephalomyelitis in the Lewis rat by oral administration of type 1 interferons

The effect of orally administered type 1 interferons on the severity of acute experimental autoimmune encephalomyelitis (EAE), a T cell-mediated autoimmune disease, was examined by inoculation of Lewis rats with guinea pig myelin basic protein (GPMBP) and complete Freund's adjuvant. Rats were fed either rat species-specific or human recombinant type 1 interferon (IFN) or mock IFN daily for 7 days preceding immunization and for 21 days thereafter. There was a significant decrease in the clinical score and inflammatory foci in animals fed 5000 units IFN compared with mock-treated animals. There was a significant decrease in clinical score and number of inflammatory foci in spinal cord in animals fed orally 5000 units human recombinant IFN-alpha PO compared with SC 5000 units recombinant human IFN-alpha. Oral administration of type 1 interferon, as opposed to subcutaneous administration, inhibited the secretion of IFN-gamma from ConA-activated draining popliteal lymph node cells compared with mock-fed animals. These experiments demonstrate that acute EAE is more effectively inhibited by equivalent amounts of orally in contrast to parenterally administered IFN-alpha. These results suggest that type 1 IFNs are active by the oral route and have significant clinical and histologic effects in acute autoimmune disease.

Inhibition of chronic relapsing experimental allergic encephalomyelitis in the Biozzi AB/H mouse

Chronic relapsing experimental allergic encephalomyelitis (CREAE) can be reproducibly induced in Biozzi AB/H mice following injection of spinal cord homogenate (SCH) emulsified in complete Freund's adjuvant (CFA). Active clinical disease is associated with mononuclear cell infiltration of the central nervous system (CNS), mainly the spinal cord. Whole brain homogenate (BH), however, failed to induce clinical or histological disease. In contrast, substituting sciatic nerve homogenate in the inoculum induced experimental allergic neuritis (EAN). Clinical disease was manifest earlier (13.1 +/- 0.3 days) than CREAE (16.2 +/- 1.4) and was accompanied by mononuclear infiltration of the peripheral nervous system (PNS). In comparison to CREAE induction, pretreating mice with SCH or BH in incomplete Freund's adjuvant (IFA) suppressed the development of SCH-induced disease. The BH was more tolerogenic than the SCH and this hyporesponsiveness was CNS antigen-specific as PNS tissue failed to inhibit the course of CREAE. Tolerance induced by pretreatment with SCH or BH in IFA was reversed by a single injection of 200 mg/kg cyclophosphamide, 2 days prior to CREAE induction. This suggests that IFA-induced hyporesponsiveness is actively regulated, possibly via the action of suppressor cells. In addition, treatment with neuroantigens in IFA appears to be mainly afferent acting as it serves to prevent initial disease induction. This treatment after immunization for CREAE, however, fails to prevent disease progression. Furthermore, treatment with CNS antigens emulsified in IFA during the post-acute remission stage appeared to synchronize and induce (32 +/- 1 days) the onset of clinical relapse, compared with untreated controls (41 +/- 5 days). This indicates that such IFA treatment has minimal value in controlling an ongoing immune disease of the CNS.

Drainage of brain extracellular fluid into blood and deep cervical lymph and its immunological significance

Cerebral extracellular fluids drain from brain to blood across the arachnoid villi and to lymph along certain cranial nerves (primarily olfactory) and spinal nerve root ganglia. Quantification of the connection to lymph in rabbit, cat and sheep, using radiolabelled albumin as a marker of flow, indicates that a minimum of 14 to 47% of protein injected into different regions of brain or cerebrospinal fluid passes through lymph. The magnitude of the outflow to lymph is at variance with the general assumption that the absence of conventional lymphatics from the brain interrupts the afferent arm of the immune response to brain antigens. The immune response to antigens (albumin or myelin basic protein) introduced into the central nervous system (CNS) has been analysed using a rat model with normal brain barrier permeability. The micro-injection of antigen into brain or cerebrospinal fluid elicits a humoral immune response, with antibody production in cervical lymph nodes and spleen, and also affects cell-mediated immunity. Furthermore, antigen may be more immunogenic when administered into the CNS than into conventional extracerebral sites. Clearly, the afferent arm of the immune response to antigens, within the CNS, is intact. Modern studies suggest that the efferent arm is also intact with passage of activated lymphocytes into the brain. Results support a new view of CNS immunology which incorporates continuous and highly regulated communication between the brain and the immune system in both health and disease.

Suppression of experimental autoimmune uveitis in rats by the oral administration of the uveitopathogenic S-antigen fragment or a cross-reactive homologous peptide

The oral administration of S-antigen fragment (a synthetic peptide designated as peptide M and known to be uveitopathogenic for rat, guinea pig, and monkey) to Lewis rats prior to challenge with an emulsion of peptide M and CFA resulted in either a total or partial suppression of experimental autoimmune uveitis (EAU), a T cell-mediated autoimmune disease studied as a model for human uveitis and experimental autoimmune pinealitis (EPA). Both the clinical and histopathologic manifestations of the disease were suppressed in a dose-dependent manner. Pinealitis associated with EAU was also suppressed by the oral administration of peptide M. Additionally, ingestion of a fragment of baker's yeast (Saccharomyces cerevisiae) histone H3, which has five consecutive amino acids identical to peptide M and which has been found to be uveitopathogenic in Lewis rats, induced tolerance to either peptide M or synthetic histone H3 peptide. In addition, the proliferative response to peptide M was inhibited in peptide M-fed rats. The suppression of EAU and in vitro lymphocyte proliferative responses to peptide M were observed to be antigen specific, since oral feeding of a control protein (BSA) exerted no suppressive effect. Furthermore, the T cells isolated from the spleen and lymph nodes of animals rendered tolerant by oral administration of peptide M can transfer protection against EAU adoptively. These results demonstrate that the oral administration of an autoantigen or its homologous peptide initiates an antigen-specific cellular mechanism which may ameliorate EAU.

Myelin basic protein infused into cerebrospinal fluid suppresses experimental autoimmune encephalomyelitis

We have evaluated the antibody and the effector T-cell responses to a single cerebrospinal fluid (CSF) infusion of myelin basic protein (MBP) in Lewis rats by measuring serum anti-MBP antibodies and clinical signs of experimental autoimmune encephalomyelitis (EAE), respectively. Some rats developed anti-MBP antibodies, but none manifested EAE in response to the primary infusion. Antibody responses to an EAE challenge 3 weeks after CSF infusion were normal, but clinical symptoms of EAE were markedly suppressed. Brain trauma at the time of MBP pretreatment enhanced this suppression. The CSF route of MBP administration is more effective in inducing suppression of EAE than peripheral routes.

Suppression of experimental allergic encephalomyelitis by MBP-coupled lymphoid cells and by MBP-liposomes: a comparison

In previous experiments, we showed that administration of myelin basic protein (MBP) inserted into phosphatidyl-serine liposomes, to susceptible animals suppressed the clinical manifestations of both acute and chronic-relapsing EAE. In this report we compare the effectiveness of treatment with MBP-liposomes and with MBP-coupled syngeneic spleen cells in EAE protection. Lewis rats treated with 150 micrograms MBP-liposomes or with 160 micrograms (35 x 10(6] MBP-coupled spleen cells, given 7 days before and 7 days after encephalitogenic challenge were equally protected against clinical EAE, when compared to untreated controls. In addition to clinical protection, in vitro proliferative responses of lymphocytes from treated rats were significantly reduced, but delayed hypersensitivity (DTH) reactions remained unaffected. Proliferation of lymphocytes from MBP-sensitized donors was inhibited by the addition of spleen cells but not of lymph node cells from treated donors. The inhibitory effect was observed with spleen cells regardless of whether the donors were treated or not, was antigen nonspecific, and localized in a radio-resistant, adherent cell population. Adoptive transfers of spleen cells from treated donors, after a 48-hr in vitro incubation with concanavalin A, showed that the cells from donors treated with MBP-coupled spleen cells, but not with MBP-liposomes, suppressed the disease in recipients, following challenge with MBP-complete Freund's adjuvant (CFA). These results suggest that two distinct mechanisms operate in the protection by MBP-coupled cells and MBP-liposomes, respectively.

Resistance to experimental autoimmune encephalomyelitis induced by neonatal tolerization to myelin basic protein: clonal elimination vs. regulation of autoaggressive lymphocytes

The target autoantigen of experimental autoimmune encephalomyelitis (EAE), myelin basic protein (MBP), appears late in ontogeny. In the rat MBP is expressed first on days 2-3 post partum, at a development stage, when self tolerance to most other autoantigens has already developed. To shed light on the cellular mechanisms that lead to immunological self tolerance to MBP, we treated neonatal rats with high doses of MBP before ontogenetic appearance of this autoantigen. We found that high doses are required to confer MBP-specific tolerance lasting until the adult life. Neonatally tolerized, adult rats are completely resistant to induction of EAE by injection of MBP in complete Freund's adjuvant (CFA). Upon MBP CFA challenge, these animals develop a limited humoral response to MBP, but are completely unreactive to MBP on the T cell level. The function of antigen-presenting cells is unchanged by neonatal tolerization, and there is no evidence for the induction of suppressive mechanisms. Transfers of large numbers of tolerized lymphocytes to normal hosts fails to interfere with EAE inducibility. Moreover, neonatally tolerized lymphocytes do not reduce MBP reactivity of primed lymph node cells or T line cells in vitro. Finally, neonatally tolerized rats are susceptible to EAE transferred by activated primed lymphocytes or by in vitro-activated MBP-specific T line cells. The apparent deletion of MBP-specific T lymphocytes in neonatally tolerized rats is in striking contrast to the physiological self tolerance to MBP, which is characterized by the presence of MBP-specific clones in the normal immune repertoire.

Regulatory circuits in autoimmunity: recruitment of counter-regulatory CD8+ T cells by encephalitogenic CD4+ T line cells

In this study, pretreatment of Lewis rats with a syngeneic encephalitogenic T cell line (S1) was found to be able to constantly induce resistance to the subsequent induction of transferred experimental autoimmune encephalomyelitis (tEAE). This treatment was capable of protecting recipient animals for at least 2-4 months. Here we show an enhanced suppressor T(anti-S1) cell activity, which can be readily detected in the lymphoid organs of animals which recovered from S1-induced tEAE, or from rats pretreated with attenuated (irradiated, fixative treated or water-lysed) S1 cells. Anti-S1 cells, which uniformly express the CD8 phenotype, were selectively stimulated to grow and expand into lines by confronting primed lymphoid cells with irradiated S1 cells in culture. The proliferative response of anti-S1 cells was independent of myelin basic protein and antigen-presenting cells, and the responses against unrelated encephalitogenic T cell lines were minimal. It was also found that none of the monoclonal antibodies tested (including CD8 and MHC class I antigen-specific antibodies) was able to block S1/anti-S1 interactions. These cells are functionally suppressive to the proliferation of S1 cells in vitro, are specifically cytolytic directed against the EAE-inducing S1 cells and are able to antagonize encephalitogenic capacity of S1 cells in vivo. In vivo elimination of the CD8+ T subset from Lewis rats, using a combined treatment of thymectomy and OX-8 antibody injection before the initial cell transfer, totally blocked the induction of resistance. Our experiments document that induction of functionally active suppressor T cells is responsible for the induced resistance observed in tEAE.

Effect of treatment with glutaraldehyde-fixed myelin basic protein-liposomes on active induction and passive transfer of experimental allergic encephalomyelitis in Lewis rats

Guinea pig myelin basic protein (MBP)-liposomes were prepared and fixed with 0.2% glutaraldehyde (GA). Lewis rats were treated with glutaraldehyde-fixed MBP-liposomes (MBP-L-GA) or with cytochrome-c-liposomes (CYC-L-GA), 7 days before and 7 days after challenge with MBP in CFA. Rats treated with MBP-L-GA, but not with CYC-L-GA, were very well protected against the clinical manifestations of EAE. The protection was better than that obtained after treatment with conventional MBP-liposomes (without glutaraldehyde). Furthermore, when grown in vitro for 72 hr in the presence of MBP, lymphocytes from rats treated with MBP-L-GA and challenged with MBP in CFA exhibited a marked decrease in their ability to transfer EAE to normal syngeneic recipients.

Restricted use of T cell receptor V genes in murine autoimmune encephalomyelitis raises possibilities for antibody therapy

Experimental allergic encephalomyelitis (EAE) is a paralytic autoimmune disease induced in susceptible animals by active immunization with myelin basic protein (MBP) or by passive transfer of MBP-specific T helper (TH) lymphocytes. We have analyzed the T cell receptor genes of 33 clonally distinct TH cells specific for a nonapeptide of MBP inducing EAE in B10.PL (H-2u) mice. All 33 TH cells used two alpha variable gene segments (V alpha 2.3, 61%; V alpha 4.2, 39%), the same alpha joining gene segment (J alpha 39), and two V beta and J beta gene segments (V beta 8.2-J beta 2.6, 79%; V beta 13-J beta 2.2, 21%). The anti-V beta 8 monoclonal antibody F23.1 was found to block completely recognition of the nonapeptide by V beta 8 TH cells in vitro and to reduce significantly the susceptibility of B10.PL mice to peptide-induced EAE.

Suppression of experimentally induced autoimmune encephalomyelitis by cytolytic T-T cell interactions

Down-regulatory phenomena have been described in several experimental models of tissue-specific, T-cell-mediated autoimmunity. For example, resistance to active induction of experimental autoimmune encephalomyelitis (EAE) can be induced by pretreating animals with non-pathogenic inocula of autoantigen or effector cells. Moreover, animals that have recovered from one EAE episode are resistant to subsequent induction of EAE. In some models, resistance to EAE has been transferred with immune cells to naive recipients. These experiments, which were based on transfers of unseparated immune cell populations, are difficult to interpret. Immune suppression circuits are known to be complex and involve various distinct cellular subsets. To further complicate the issue, resistance to EAE can be transferred not only by suppressor cells, but also by encephalitogenic effector cells injected in 'subclinical' doses. We describe now the isolation of homogeneous T lymphocyte lines from the spleens of Lewis rats that had recovered from T-cell-mediated EAE (tEAE) caused by the MBP-specific T cell line S1. These spleen-derived T line cells express the CD8 phenotype and specifically respond to determinants on the inducing S1 line, but not to the autoantigen MBP. Furthermore, the anti-S1 cells selectively lyse the encephalitogenic S1 T line in vitro and efficiently neutralize their encephalitogenic capacity in vivo.

Suppression of experimental autoimmune encephalomyelitis by the oral administration of myelin basic protein

The oral administration of myelin basic protein (MBP) to Lewis rats prior to an encephalitogenic challenge resulted in total inhibition or a significant delay in the onset of experimental autoimmune encephalomyelitis (EAE). In vitro lymphocyte proliferative responses to MBP were significantly decreased in MBP-fed rats when compared with vehicle-fed controls. Suppression of EAE and in vitro proliferative responses to MBP were observed to be antigen specific, since oral feeding of a control protein exerted no suppressive effect. Moreover, the specificity of MBP-induced oral tolerance was shown to be species specific, since feeding guinea pig MBP (GPMBP) or human MBP (HuMBP) induced protection only against a GPMBP or HuMBP challenge, respectively. Conversely, Lewis rats could not be orally tolerized to the self antigen rat MBP.

Demyelination and neurological signs in experimental allergic encephalomyelitis

Because of the reported absence of demyelination in some animals with neurological signs of experimental allergic encephalomyelitis (EAE), it has been suggested that these signs are not due to demyelination. The present study demonstrates that there is ample demyelination in the central nervous system (CNS) and peripheral nervous system (PNS) to account for the neurological signs in rats with myelin basic protein (MBP)-induced acute EAE as well as in rats and rabbits with whole-spinal-cord-induced acute EAE. The main reasons for failure to detect demyelination in animals with neurological signs of EAE appear to be inadequate histological techniques and incomplete examination of the nervous system, particularly the PNS and the lumbar, sacral and coccygeal segments of the spinal cord.

Protection against allergic encephalomyelitis by recruitment of myelin basic protein reactive lymphocytes into a single lymph node

The efferent popliteal lymphatic of sheep was cannulated and sheep myelin basic protein (BP) was repeatedly injected into the drainage site of that popliteal node. All the recirculating lymphocytes leaving the node were removed from the sheep via the efferent cannula. Sheep undergoing such chronic stimulation and drainage failed to develop allergic encephalomyelitis when challenged with an encephalitogenic inoculum in the contralateral leg. Chronic stimulation without subsequent removal of lymphocytes did not protect animals against challenge. These results suggest that protection is due to the stimulation, recruitment and removal of specific BP reactive cells from the recirculating lymphocyte pool. Possible therapeutic applications in multiple sclerosis are discussed.

Conduction block due to demyelination at the ventral root exit zone in experimental allergic encephalomyelitis

Histological and electrophysiological studies were performed in Lewis rats with experimental allergic encephalomyelitis (EAE) to determine the cause of the neurological signs. The ventral root exit zone of the spinal cord was shown to be a major site of demyelination and conduction block. It is concluded that demyelination-induced conduction block in this region is an important cause of hindlimb weakness and paralysis in Lewis rats with EAE.

CSF myelin basic protein in multiple sclerosis

Cerebrospinal fluid (CSF) from 221 patients with multiple sclerosis (MS) and 85 patients with other neurological disorders (OND) was examined using a competitive radioimmunoassay for myelin basic protein (MBP) immunoreactivity. MBP was found in 46 of 55 MS patients (84%) examined within six weeks of relapse but in only 11 of 85 patients (13%) with OND. There was a significant correlation between the concentration of MBP in the CSF and relapse severity in patients seen within four weeks of the onset of symptoms (p less than 0.01). Of 44 patients in remission, MBP was detected in 12, and these patients had a significantly higher tendency to subsequent relapse (p less than 0.05). In 72 patients with progressive disease the presence of MBP in the CSF reflected the confidence of clinical diagnosis. The results of this study suggest that measurement of MBP in the CSF gives an objective method of monitoring disease activity in patient with MS.

Measurement of myelin basic protein by radioimmunoassay in closed head trauma, multiple sclerosis and other neurological diseases

A double antibody sequential radioimmunoassay for human myelin basic protein (MBP) has been developed. The assay utilizes a rabbit antibody to human MBP and purified rabbit MBP as the radiolabelled antigen. This assay was used to analyze cerebrospinal fluid (CSF) from 22 patients with severe head injury, 61 other cases of various neurological disorders, and 106 normal controls. The results showed that closed head trauma caused moderate to severe elevations in CSF MBP, and elevated CSF MBP was detectable in several diseases which involve CNS myelin.