Autoimmunity Increases Susceptibility to and Mortality from Sepsis.

We recently demonstrated how sepsis influences the subsequent development of experimental autoimmune encephalomyelitis (EAE) presented a conceptual advance in understanding the postsepsis chronic immunoparalysis state. However, the reverse scenario (autoimmunity prior to sepsis) defines a high-risk patient population whose susceptibility to sepsis remains poorly defined. In this study, we present a retrospective analysis of University of Iowa Hospital and Clinics patients demonstrating increased sepsis prevalence among multiple sclerosis (MS), relative to non-MS, patients. To interrogate how autoimmune disease influences host susceptibility to sepsis, well-established murine models of MS and sepsis and EAE and cecal ligation and puncture, respectively, were used. EAE, relative to non-EAE, mice were highly susceptible to sepsis-induced mortality with elevated cytokine storms. These results were further recapitulated in LPS and Streptococcus pneumoniae sepsis models. This work highlights both the relevance of identifying highly susceptible patient populations and expands the growing body of literature that host immune status at the time of septic insult is a potent mortality determinant.

Pertussis Toxin Inhibits Encephalitogenic T-Cell Infiltration and Promotes a B-Cell-Driven Disease during Th17-EAE.

Pertussis toxin (PTX) is a required co-adjuvant for experimental autoimmune encephalomyelitis (EAE) induced by immunization with myelin antigen. However, PTX's effects on EAE induced by the transfer of myelin-specific T helper cells is not known. Therefore, we investigated how PTX affects the Th17 transfer EAE model (Th17-EAE). We found that PTX significantly reduced Th17-EAE by inhibiting chemokine-receptor-dependent trafficking of Th17 cells. Strikingly, PTX also promoted the accumulation of B cells in the CNS, suggesting that PTX alters the disease toward a B-cell-dependent pathology. To determine the role of B cells, we compared the effects of PTX on Th17-EAE in wild-type (WT) and B-cell-deficient (µMT) mice. Without PTX treatment, disease severity was equivalent between WT and µMT mice. In contrast, with PTX treatment, the µMT mice had significantly less disease and a reduction in pathogenic Th17 cells in the CNS compared to the WT mice. In conclusion, this study shows that PTX inhibits the migration of pathogenic Th17 cells, while promoting the accumulation of pathogenic B cells in the CNS during Th17-EAE. These data provide useful methodological information for adoptive-transfer Th17-EAE and, furthermore, describe another important experimental system to study the pathogenic mechanisms of B cells in multiple sclerosis.

Bcl11b prevents fatal autoimmunity by promoting Treg cell program and constraining innate lineages in Treg cells.

Regulatory T (Treg) cells are essential for peripheral tolerance and rely on the transcription factor (TF) Foxp3 for their generation and function. Several other TFs are critical for the Treg cell program. We found that mice deficient in Bcl11b TF solely in Treg cells developed fatal autoimmunity, and Bcl11b-deficient Treg cells had severely altered function. Bcl11b KO Treg cells showed decreased functional marker levels in homeostatic conditions, inflammation, and tumors. Bcl11b controlled expression of essential Treg program genes at steady state and in inflammation. Bcl11b bound to genomic regulatory regions of Treg program genes in both human and mouse Treg cells, overlapping with Foxp3 binding; these genes showed altered chromatin accessibility in the absence of Bcl11b. Additionally, Bcl11b restrained myeloid and NK cell programs in Treg cells. Our study provides new mechanistic insights on the Treg cell program and identity control, with major implications for therapies in autoimmunity and cancer.

T-Cell-Intrinsic Receptor Interacting Protein 2 Regulates Pathogenic T Helper 17 Cell Differentiation.

Receptor interacting protein 2 (RIP2) plays a role in sensing intracellular pathogens, but its function in T cells is unclear. We show that RIP2 deficiency in CD4+ T cells resulted in chronic and severe interleukin-17A-mediated inflammation during Chlamydia pneumoniae lung infection, increased T helper 17 (Th17) cell formation in lungs of infected mice, accelerated atherosclerosis, and more severe experimental autoimmune encephalomyelitis. While RIP2 deficiency resulted in reduced conventional Th17 cell differentiation, it led to significantly enhanced differentiation of pathogenic (p)Th17 cells, which was dependent on RORα transcription factor and interleukin-1 but independent of nucleotide oligomerization domain (NOD) 1 and 2. Overexpression of RIP2 resulted in suppression of pTh17 cell differentiation, an effect mediated by its CARD domain, and phenocopied by a cell-permeable RIP2 CARD peptide. Our data suggest that RIP2 has a T cell-intrinsic role in determining the balance between homeostatic and pathogenic Th17 cell responses.

CNS-targeted autoimmunity leads to increased influenza mortality in mice.

The discovery that central nervous system (CNS)-targeted autoreactive T cells required a process of licensing in the lung revealed an unexpected relationship between these organs. The clinical and immunological significance of this finding is bidirectional in that it showed not only a mechanism by which T cells become pathogenic before entering the CNS, but also the potential for this process to influence lung immunity as well. Epidemiological studies have shown that people with multiple sclerosis (MS) suffer from increased morbidity and mortality from infectious diseases, independent of immunosuppressive therapies. Respiratory infections account for a large percentage of deaths of people with MS. In this study, to investigate the mechanisms responsible for this enhanced susceptibility, we established a comorbid model system in which mice with experimental autoimmune encephalomyelitis (EAE) were administered a sublethal dose of influenza. Whereas mice with either EAE alone or influenza alone survived, 70% of comorbid mice died as a result of uncontrolled viral replication. Immunological analyses revealed that the induction of EAE led to a surprising alteration of the lung milieu, converting an effective stimulatory influenza-reactive environment into a suppressive one. These results provide mechanistic information that may help to explain the unexpected immunological interactions.

Chronic iron overload induces gender-dependent changes in iron homeostasis, lipid peroxidation and clinical course of experimental autoimmune encephalomyelitis.

To analyze iron- and gender-dependent mechanisms possibly involved in pathogenesis of multiple sclerosis (MS) in this study we evaluated the effects of iron overload (IO) on iron status and lipid peroxidation processes (LPO) in tissues of female and male DA rats during chronic relapsing experimental autoimmune encephalomyelitis, a well-established MS animal model. Rats were treated by iron sucrose (75mg/kg bw/day) or with saline solution during two weeks before the sensitization with bovine brain homogenate in complete Freund's adjuvant. Clinical signs of EAE were monitored during 29 days. Serum and tissues of CNS and liver were sampled before immunization and at day 13th post immunization (during acute phase of EAE). The determination of ferritin, iron, malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) and evaluation of histopathology were performed by ELISA, ICP spectrometry and immunohistochemistry. Results showed that IO in female EAE rats accelerated the onset of disease. In contrast, in male rats it accelerated the progression of disease and increased the mortality rate. During acute phase of EAE female IO rats sequestered more Fe in the liver, spinal cord and in the brain and produced more ferritin than male EAE rats. Male rats, however, reacted on IO by higher production of MDA or 4-HNE in the neural tissues and showed greater signs of plaque formation and gliosis in spinal cord. The data point to sexual dimorphism in mechanisms that regulate peripheral and brain iron homeostasis and imply that men and women during MS might be differentially vulnerable to exogenous iron overload.

Grb2 Is Important for T Cell Development, Th Cell Differentiation, and Induction of Experimental Autoimmune Encephalomyelitis.

The small adaptor protein growth factor receptor-bound protein 2 (Grb2) modulates and integrates signals from receptors on cellular surfaces in inner signaling pathways. In murine T cells, Grb2 is crucial for amplification of TCR signaling. T cell-specific Grb2(fl/fl) Lckcre(tg) Grb2-deficient mice show reduced T cell numbers due to impaired negative and positive selection. In this study, we found that T cell numbers in Grb2(fl/fl) CD4cre(tg) mice were normal in the thymus and were only slightly affected in the periphery. Ex vivo analysis of CD4(+) Th cell populations revealed an increased amount of Th1 cells within the CD4(+) population of Grb2(fl/fl) CD4cre(tg) mice. Additionally, Grb2-deficient T cells showed a greater potential to differentiate into Th17 cells in vitro. To test whether these changes in Th cell differentiation potential rendered Grb2(fl/fl) CD4cre(tg) mice more prone to inflammatory diseases, we used the murine Th1 cell- and Th17 cell-driven model of experimental autoimmune encephalomyelitis (EAE). In contrast to our expectations, Grb2(fl/fl) CD4cre(tg) mice developed a milder form of EAE. The impaired EAE disease can be explained by the reduced proliferation rate of Grb2-deficient CD4(+) T cells upon stimulation with IL-2 or upon activation by allogeneic dendritic cells, because the activation of T cells by dendritic cells and the subsequent T cell proliferation are known to be crucial factors for the induction of EAE. In summary, Grb2-deficient T cells show defects in T cell development, increased Th1 and Th17 cell differentiation capacities, and impaired proliferation after activation by dendritic cells, which likely reduce the clinical symptoms of EAE.

Variable behavior and complications of autologous bone marrow mesenchymal stem cells transplanted in experimental autoimmune encephalomyelitis.

Autologous bone marrow stromal cells (BMSCs) offer significant practical advantages for potential clinical applications in multiple sclerosis (MS). Based on recent experimental data, a number of clinical trials have been designed for the intravenous (IV) and/or intrathecal (ITH) administration of BMSCs in MS patients. Delivery of BMSCs in the cerebrospinal fluid via intracerebroventricular (ICV) transplantation is a useful tool to identify mechanisms underlying the migration and function of these cells. In the current study, BMSCs were ICV administered in severe and mild EAE, as well as naive animals; neural precursor cells (NPCs) served as cellular controls. Our data indicated that ICV-transplanted BMSCs significantly ameliorated mild though not severe EAE. Moreover, BMSCs exerted significant anti-inflammatory effect on spinal cord with concomitant reduced axonopathy only in the mild EAE model. BMSCs migrated into the brain parenchyma and, depending on their cellular density, within brain parenchyma formed cellular masses characterized by focal inflammation, demyelination, axonal loss and increased collagen-fibronectin deposition. These masses were present in 64% of ICV BMASC-transplanted severe EAE animals whereas neither BMSCs transplanted in mild EAE cases nor the NPCs exhibited similar behavior. BMSCs possibly exerted their fibrogenic effect via both paracrine and autocrine manner, at least partly due to up-regulation of connective tissue growth factor (CTGF) under the trigger of TGFb1. Our findings are of substantial relevance for clinical trials in MS, particularly regarding the possibility that ICV transplanted BMSCs entering the inflamed central nervous system may exhibit - under conditions - a local pathology of yet unknown consequences.

Anaphylaxis and mortality induced by treatment of mice with anti-VLA-4 antibody and pertussis toxin.

Ab-mediated blockade of the adhesion molecule VLA-4 has been shown to ameliorate disease in human multiple sclerosis patients and experimental autoimmune encephalomyelitis (EAE) animal models. We wanted to determine whether anti-VLA-4 Ab treatment affected the function and persistence of autoreactive T cells in mice with EAE. Unexpectedly, we observed a high level of mortality in anti-VLA-4 mAb (PS/2)-treated mice with actively induced EAE despite decreased disease severity. Investigation of the underlying mechanism showed that injection of PS/2 mAb in combination with pertussis toxin resulted in anaphylaxis and mortality. Furthermore, the data showed that CD4(+) T cells were required for this effect and suggested a role for IL-1ß and TNF-α in the underlying pathology. The results reveal a previously not appreciated deleterious effect of anti-VLA-4 Ab treatment in combination with exposure to pertussis toxin.

Specific and strain-independent effects of dexamethasone in the prevention and treatment of experimental autoimmune encephalomyelitis in rodents.

Experimental autoimmune encephalomyelitis in rodents (EAE) is a generally accepted in vivo model for immunopathogenic mechanisms underlying multiple sclerosis (MS). There are, however, different forms of rodent EAE, and therapeutic regimens may affect these forms differently. We have therefore tested the effects of dexamethasone (Dex) and found that both prophylactic and early therapeutic regimens were effective in suppressing the development of monophasic EAE in myelin basic protein-immunized Lewis rats, the relapsing-remitting forms of EAE induced in SJL mice by proteolipid protein and in DA rats by syngeneic spinal cord homogenate, and the progressive forms induced in C57BL/6 and DBA/1 mice by immunization with myelin oligodendrocyte glycoprotein. In addition, prophylactically administered Dex suppressed histological and immunological features of EAE such as spinal cord infiltration of inflammatory cells and the increased frequency of autoantigen-specific interferon-gamma-secreting lymph node mononuclear cells. The present data reproduced in rodent EAE models some of the beneficial effects observed with glucocorticoids in MS. This strengthens the validity of these five models as in vivo predictors of drug efficacy in at least some variants of human MS. Better understanding of the clinical and immunopharmacologic features of these models might prove useful when testing new drug candidates for MS treatment.

Stromal interaction molecules 1 and 2 are key regulators of autoreactive T cell activation in murine autoimmune central nervous system inflammation.

Calcium (Ca(2+)) signaling in T lymphocytes is essential for a variety of functions, including the regulation of differentiation, gene transcription, and effector functions. A major Ca(2+) entry pathway in nonexcitable cells, including T cells, is store-operated Ca(2+) entry (SOCE), wherein depletion of intracellular Ca(2+) stores upon receptor stimulation causes subsequent influx of extracellular Ca(2+) across the plasma membrane. Stromal interaction molecule (STIM) 1 is the Ca(2+) sensor in the endoplasmic reticulum, which controls this process, whereas the other STIM isoform, STIM2, coregulates SOCE. Although the contribution of STIM molecules and SOCE to T lymphocyte function is well studied in vitro, their significance for immune processes in vivo has remained largely elusive. In this study, we studied T cell function in mice lacking STIM1 or STIM2 in a model of myelin-oligodendrocyte glycoprotein (MOG(35-55))-induced experimental autoimmune encephalomyelitis (EAE). We found that STIM1 deficiency significantly impaired the generation of neuroantigen-specific T cell responses in vivo with reduced Th1/Th17 responses, resulting in complete protection from EAE. Mice lacking STIM2 developed EAE, but the disease course was ameliorated. This was associated with a reduced clinical peak of disease. Deficiency of STIM2 was associated with an overall reduced proliferative capacity of lymphocytes and a reduction of IFN-gamma/IL-17 production by neuroantigen-specific T cells. Neither STIM1 nor STIM2 deficiency altered the phenotype or function of APCs. These findings reveal a crucial role of STIM-dependent pathways for T cell function and activation under autoimmune inflammatory conditions, establishing them as attractive new molecular therapeutic targets for the treatment of inflammatory and autoimmune disorders.

Quantitative and qualitative differences in the in vivo response of NKT cells to distinct alpha- and beta-anomeric glycolipids.

NKT cells represent a unique subset of immunoregulatory T cells that recognize glycolipid Ags presented by the MHC class I-like molecule CD1d. Because of their immunoregulatory properties, NKT cells are attractive targets for the development of immunotherapies. The prototypical NKT cell ligand alpha-galactosylceramide (alpha-GalCer), originally isolated from a marine sponge, has potent immunomodulatory activities in mice, demonstrating therapeutic efficacy against metastatic tumors, infections, and autoimmune diseases, but also has a number of adverse side effects. In vivo administration of alpha-GalCer to mice results in the rapid activation of NKT cells, which is characterized by cytokine secretion, surface receptor down-regulation, expansion, and secondary activation of a variety of innate and adaptive immune system cells. In this study, we have evaluated the in vivo immune response of mice to a set of structural analogues of alpha-GalCer. Our results show that, contrary to current thinking, beta-anomeric GalCer can induce CD1d-dependent biological activities in mice, albeit at lower potency than alpha-anomeric GalCer. In addition, we show that the response of NKT cells to distinct GalCer differs not only quantitatively, but also qualitatively. These findings indicate that NKT cells can fine-tune their immune responses to distinct glycolipid Ags in vivo, a property that may be exploited for the development of effective and safe NKT cell-based immunotherapies.

Cutting edge: ligation of the glucocorticoid-induced TNF receptor enhances autoreactive CD4+ T cell activation and experimental autoimmune encephalomyelitis.

The glucocorticoid-induced TNFR (GITR) is expressed at high levels on resting CD4(+)CD25(+) T regulatory (T(R)) cells and regulates their suppressive phenotype. Accordingly, we show that anti-GITR mAb treatment of SJL mice with proteolipid protein 139-151-induced experimental autoimmune encephalomyelitis significantly exacerbated clinical disease severity and CNS inflammation, and induced elevated levels of Ag-specific T cell proliferation and cytokine production. Interestingly, prior depletion of T(R) cells failed to result in exacerbated experimental autoimmune encephalomyelitis suggesting alternative targets for the anti-GITR mAb treatment. Importantly, naive CD4(+)CD25(-) T cells up-regulated GITR expression in an activation-dependent manner and anti-GITR mAb treatment enhanced the level of CD4(+) T cell activation, proliferation, and cytokine production in the absence of T(R) cells both in vivo and in vitro. Taken together, these findings suggest a dual functional role for GITR as GITR cross-linking both inactivates T(R) cells and increases CD4(+)CD25(-) T cell effector function, thus enhancing T cell immunity.

Suppressive DNA vaccination in myelin oligodendrocyte glycoprotein peptide-induced experimental autoimmune encephalomyelitis involves a T1-biased immune response.

Vaccination with DNA encoding a myelin basic protein peptide suppresses Lewis rat experimental autoimmune encephalomyelitis (EAE) induced with the same peptide. Additional myelin proteins, such as myelin oligodendrocyte glycoprotein (MOG), may be important in multiple sclerosis. Here we demonstrate that DNA vaccination also suppresses MOG peptide-induced EAE. MOG(91-108) is encephalitogenic in DA rats and MHC-congenic LEW.1AV1 (RT1(av1)) and LEW.1N (RT1(n)) rats. We examined the effects of DNA vaccines encoding MOG(91-108) in tandem, with or without targeting of the hybrid gene product to IgG. In all investigated rat strains DNA vaccination suppressed clinical signs of EAE. There was no requirement for targeting the gene product to IgG, but T1-promoting CpG DNA motifs in the plasmid backbone of the construct were necessary for efficient DNA vaccination, similar to the case in DNA vaccination in myelin basic protein-induced EAE. We failed to detect any effects on ex vivo MOG-peptide-induced IFN-gamma, TNF-alpha, IL-6, IL-4, IL-10, and brain-derived neurotropic factor expression in splenocytes or CNS-derived lymphocytes. In CNS-derived lymphocytes, Fas ligand expression was down-regulated in DNA-vaccinated rats compared with controls. However, MOG-specific IgG2b responses were enhanced after DNA vaccination. The enhanced IgG2b responses together with the requirement for CpG DNA motifs in the vaccine suggest a protective mechanism involving induction of a T1-biased immune response.

In vivo upregulation of interleukin-4 is one mechanism underlying the immunoregulatory effects of 1,25-dihydroxyvitamin D(3).

The active form of vitamin D (1,25-(OH)(2)D(3)) is a potent immune system regulator. In vivo the oral administration of 1, 25-(OH)(2)D(3) completely prevents experimental autoimmune encephalomyelitis (EAE), significantly prolongs allograft survival, and prevents collagen-induced arthritis. 1,25-(OH)(2)D(3) given to mice increased IL-4 protein and transcript levels. We have now tested the efficacy of 1,25-(OH)(2)D(3) on EAE development and allograft survival in IL-4-deficient [knockout (ko)] mice. 1, 25-(OH)(2)D(3) was found to be much less effective in the absence of IL-4, suggesting that IL-4 production is a significant factor in the action of 1,25-(OH)(2)D(3) on the immune system.

In vivo administration of anti-CD4 monoclonal antibody prolongs survival in longtailed macaques with experimental allergic encephalomyelitis.

The in vivo administration of monoclonal antibody (mAb) to the CD4 antigen associated with helper T cells has been successful in prolonging the survival of nonhuman primates with experimental allergic encephalomyelitis (EAE). EAE was induced in 17 outbred longtailed macaques (Macaca fascicularis) by inoculation of homologous myelin basic protein (BP) in complete Freund's adjuvant (CFA). Treatment was begun at the onset of clinical signs. Eleven animals were treated with anti-CD4 mAb Leu3a (eight) or OKT4a (three). Of the six control animals, two received anti-CD8 mAb (Leu2a), and four were treated with saline. Specific T- and B-cell subsets which have been implicated in the development of EAE were monitored throughout the course of the disease by one- and two-color immunofluorescence (IF). The monkey anti-BP antibody and anti-mouse immunoglobulin (IgG) responses were measured by enzyme-linked immunoassay (ELISA) techniques, as were the levels of free-circulating murine IgG. The nature of the infiltrating lymphocytes in the brain was evaluated histologically post mortem. Our results indicate that anti-CD4 mAb can prolong survival and in some cases completely reverse the clinical appearance of the disease; however, relapses did occur. Treatments with Leu3a or OKT4a anti-CD4 mAbs reversed the ongoing depletion of CD4+ and CD8+ cells caused by the development of EAE and appeared to reduce the size and degree of inflammation in brain lesions. These treatments did not induce immunologic tolerance to mouse IgG since all of the anti-CD4-treated animals produced high titers of anti-mouse IgG antibodies. Treatment with Leu2a (anti-CD8) had no effect on the development of EAE. These results suggest that CD4+ cells are important to the pathogenesis of EAE in macaques and that manipulation of this subset with monoclonal antibodies may provide effective treatment of human demyelinating disease.

[Allergic encephalomyelitis in guinea pigs on the intracutaneous and subcutaneous administration of fragment 114-122 of the human myelin cationic protein]. / Allergicheskii éntsefalomielit u morskikh svinok pri vnutrikozhnom i podkozhnom vvedenii fragmenta 114-122 kationnogo belka mielina cheloveka.

Single intracutaneous injection of 30 micrograms of human basic myelin protein peptide 114-122 (H-Phe-Ser-Trp-Gly-Ala-Glu-Gly-Gln-Arg-OH) with Freund adjuvant induced the onset of encephalomyelitis on day 9-19 after the injection. The lethality was 33%. In autumn the disease was more severe than in summer.

Effect of splenectomy on the development of experimental autoimmune encephalomyelitis in rats with different genetic background.

We studied the effect of total or partial splenectomy on experimental autoimmune encephalomyelitis (EAE) development in rats with different genetic background after immunization with guinea pig basic encephalitogenic protein in Freund's complete adjuvant. The operations did not affect some strains with a high susceptibility to EAE but may have reduced the EAE development in the Fischer strain, which shows only a weak susceptibility. In some hybrids and backcrosses, but not in others, splenectomy resulted in a clear-cut reduction of neurological signs of EAE. This effect may be ascribed to the elimination of contrasuppressive cell populations.

Effect of indomethacin treatment upon actively-induced and transferred experimental allergic encephalomyelitis (EAE) in Lewis rats.

Daily administration of indomethacin (5 mg/kg) to Lewis rats from day 7 through day 21 following sensitization to guinea-pig spinal cord neural antigen plus Freund's complete adjuvant (FCA) resulted in an aggravation of clinical signs of EAE accompanied by a higher mortality. In contrast, lymph node cells (LNC) from sensitized and drug-treated donor rats showed decreased EAE transfer activity. The in vitro Con A response of LNC from sensitized, indomethacin-treated rats was comparable to those of normal LNC or LNC from sensitized animals only. The spleen cell response of sensitized rats was significantly lower than the response seen in normal animals, but was returned to normal levels in sensitized, indomethacin-treated animals. We believe these observations reflect an indomethacin-mediated diminished accumulation of EAE effector cells within peripheral lymph node tissues together with abrogation of splenic suppressor cell activity by indomethacin-mediated inhibition of prostaglandin (PG) synthesis in Lewis rats sensitized and treated with this drug under the conditions defined.

Ameliorating effects of hyperbaric oxygenation on experimental allergic encephalomyelitis.

The effect of hyperbaric oxygenation (OHP) on survival and quality of survival of guinea pigs afflicted with experimental allergic encephalomyelitis (EAE) was investigated. EAE was induced in Hartley and Strain 13 animals by intradermal injections of whole guinea pig spinal cord in complete Freund's adjuvant. The inoculated animals were divided into control and treatment groups; the treated animals received OHP in a variety of treatment schedules. Clinical signs of EAE were quantitated and mean survival times were measured. When Hartley animals were exposed to 100% O2 at 2.5 atmospheres absolute (ATA) for 2 hr/day from 5--19 days postinoculation, the mean survival time (+/- SE) was 19.1 +/- 1.6 days relative to 15.7 +/- 0.7 days in the control (p less than 0.050). When Strain 13 guinea pigs were treated with 100% O2 at 2ATA for 4 hr/day on 5--16 days, the mean survival time was 21.6 +/- 0.6 days compared to 16.0 +/- 0.4 days for the control (p less than 0.001). Clinical sign measurements demonstrated that the onset of EAE in the treated animals of both strains occurred between 4--6 days after these signs became detectable in control animals. These results suggest that OHP therapy can ameliorate EAE in afflicted guinea pigs.