Neuroendocrine modulation of chronic relapsing experimental autoimmune encephalomyelitis: a critical role for the hypothalamic-pituitary-adrenal axis

Murine relapsing EAE can be profoundly suppressed by restraint stress (RST) administered beginning prior to neuroantigen immunization. This study determined what hormone pathway(s) mediate disease suppression. Our results showed that nadolol (NAD), a beta2-adrenergic antagonist, did not reverse the RST-induced suppression of EAE. However, administration of either RU486 or aminoglutethimide, which block the action of peripheral glucocorticoids, resulted in a partial reversal of EAE suppression. Administration of exogenous corticosterone mimicked the effects of RST, in terms of suppression of EAE, decrease in lymphoid cell numbers and decrease in Thl cytokine production. Therefore, the HPA axis plays a more profound role in the RST-induced suppression of EAE than does the sympathetic nervous system.

Oral Administration of Myelin Basic Protein Is Superior to Myelin in Suppressing Established Relapsing Experimental Autoimmune Encephalomyelitis

Oral administration of a myelin component, myelin basic protein (MBP), induces immunological unresponsiveness to CNS Ags and ameliorates murine relapsing experimental autoimmune encephalomyelitis (REAE). However, a recent clinical trial in which multiple sclerosis patients were treated with repeated doses of oral myelin was unsuccessful in reducing disease exacerbations. Therefore, we directly compared the tolerizing capacity of myelin vs MBP during REAE in B10.PL mice. Oral administration of high doses of myelin, either before disease induction or during REAE, did not provide protection from disease or decrease in vitro T cell responses. In contrast, repeated oral administration of high doses of MBP suppressed established disease and MBP-specific T cell proliferation and cytokine responses. The frequency of IL-2-, IFN-γ-, and IL-5-secreting MBP-specific T cells declined with MBP feeding, implicating anergy and/or deletion as the mechanism(s) of oral tolerance after high Ag doses. We have previously shown that the dosage and timing of Ag administration are critical parameters in oral tolerance induction. Studies presented here demonstrate that Ag homogeneity is also important, i.e., homogeneous Ag (MBP) is more effective at inducing oral tolerance than heterogeneous Ag (myelin).

Oral administration of myelin basic protein is superior to myelin in suppressing established relapsing experimental autoimmune encephalomyelitis

Oral administration of a myelin component, myelin basic protein (MBP), induces immunological unresponsiveness to CNS Ags and ameliorates murine relapsing experimental autoimmune encephalomyelitis (REAE). However, a recent clinical trial in which multiple sclerosis patients were treated with repeated doses of oral myelin was unsuccessful in reducing disease exacerbations. Therefore, we directly compared the tolerizing capacity of myelin vs MBP during REAE in B10.PL mice. Oral administration of high doses of myelin, either before disease induction or during REAE, did not provide protection from disease or decrease in vitro T cell responses. In contrast, repeated oral administration of high doses of MBP suppressed established disease and MBP-specific T cell proliferation and cytokine responses. The frequency of IL-2-, IFN-gamma-, and IL-5-secreting MBP-specific T cells declined with MBP feeding, implicating anergy and/or deletion as the mechanism(s) of oral tolerance after high Ag doses. We have previously shown that the dosage and timing of Ag administration are critical parameters in oral tolerance induction. Studies presented here demonstrate that Ag homogeneity is also important, i.e., homogeneous Ag (MBP) is more effective at inducing oral tolerance than heterogeneous Ag (myelin).

Oral tolerance in the treatment of inflammatory autoimmune diseases

Oral tolerance refers to the oral administration of protein antigens, which induces a state of systemic nonresponsiveness specific for the fed antigen. This method of inducing immune non-responsiveness has been applied to the prevention and treatment of experimental animal models of autoimmune disease. Extensive research in this area over the past ten years has led to the conclusion that two mechanisms are operative in the mediation of oral tolerance--active suppression and clonal anergy/deletion. A number of factors have been identified that determine which mechanism of tolerance is operative--antigen dose, antigen form, and the timing of antigen administration. Work from these animal models has recently been extended into human clinical trials of multiple sclerosis, rheumatoid arthritis, diabetes, uveitis, and allergy, with differing degrees of success. In this review, a discussion is provided of the animal model systems where oral tolerance has been applied and the clinical trials where an oral tolerization approach has been attempted. Moreover, recent mechanistic studies are reviewed and a model proposed for the induction of oral tolerance.

Neuroendocrine influences on experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE), a model for human multiple sclerosis, is an inflammatory disease of the CNS mediated by autoreactive T lymphocytes directed against the neuroantigen, myelin basic protein (MBP). EAE is inducible in the Lewis rat, which exhibits an acute monophasic disease, and in selected mouse strains, which show a remitting-relapsing or chronic course of paralysis. We examined the effects of neuroendocrine modulation by restraint stress on these models of EAE. In Lewis rats, daily cycles of restraint resulted in significant suppression of both clinical and histopathologic changes of EAE. Suppression of EAE was more pronounced in the female than in the male rat, which follows from the higher endogenous corticosterone levels in the female. Mechanistic studies suggested that stress affected the processing of MBP or the T-cell idiotype. In the relapsing murine model of EAE, B10.PL mice were restrained beginning either before MBP challenge or after the establishment of relapsing disease. We observed a striking inhibition of EAE clinical signs in mice stressed before challenge relative to nonstressed controls. Interestingly, approximately 10 days after termination of the stress period, clinical signs returned and were as severe or more severe than in control nonstressed animals. Stress administered after relapsing EAE was established had no protective effect. In vitro parameters revealed that only stress initiated before disease induction significantly reduced the frequency of MBP-specific lymphocytes in the spleen and lymph nodes. Both Th1 and Th2 cytokine responses were suppressed in stressed mice. T-cell receptor transgenic mice exposed to restraint showed a marked decreased in the number and functional activity of transgene-positive lymphocytes. In summary, elevated levels of endogenous neuroendocrine hormones exert a profoundly suppressive effect on both acute and chronic models of autoimmune CNS injury.

Is Spinal Cord Injury an Autoimmune Disorder?

Cross-talk between cells of the nervous and immune systems is an emerging concept in neurotrauma research. Previously, neuroimmunological approaches in brain and spinal cord injury have focused on the functional consequences of macrophage and microglial activation. These cells constitute the natural, or innate, branch of CNS immunity and respond to injury or infection in a nonspecific fashion. Recent evidence, however, has shown that T-lymphocytes may also play a significant role in spinal cord injury. Once activated, T- and B-lymphocytes orchestrate the complex functions of the inflammatory response. Acquired immunity is readily induced against “non-self,” or foreign, antigens, although “self-reactive” lymphocytes are present in normal individuals, providing the potential for the onset of autoimmunity. Trauma to or infection in the CNS may release “self” antigens normally sequestered behind the blood-brain barrier that can trigger lymphocyte activation. This article addresses the potential pathological and physiological implications of lymphocyte activation induced by traumatic spinal cord injury. NEUROSCIENTIST 4:71-76, 1998

Oral tolerance as therapy for experimental autoimmune encephalomyelitis and multiple sclerosis: demonstration of T cell anergy

Experimental autoimmune encephalomyelitis (EAE) is an important model for developing therapies for multiple sclerosis (MS). The oral administration of the central nervous system antigen, myelin basic protein (MBP), to Lewis rats and susceptible mouse strains prior to MBP immunization prevents the induction of EAE. Clinical trials administering myelin orally to MS patients have met with only partial success, and thus require that oral tolerance be further studied to improve this treatment strategy. Clonal anergy, clonal deletion, immune deviation from Th1 to Th2 T cell subsets, and active suppression by TGF-beta-secreting T cells have all been implicated as possible mechanisms in oral tolerance. Which mechanism predominates depends on antigen dosage, frequency of feeding, and timing of antigen administration. In this study, we have characterized T cells derived from MBP-fed rats and determined the level of their unresponsiveness. Myelin basic protein-specific T cells are indeed present although in reduced numbers in lymphoid tissue of orally tolerized animals. Following several cell divisions in the presence of IL-2, these MBP-specific T cells undergo a dramatic reversal of unresponsiveness, proliferate in response to MBP and are capable of transferring EAE. These results support clonal anergy as an important mechanism for oral tolerance. Recent developments in clinical trials of oral tolerance are described.

Spinal cord neuropathology in rat experimental autoimmune encephalomyelitis: modulation by oral administration of myelin basic protein

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory disease of the central nervous system (CNS) in which clinical neurological signs and histopathologic changes of disease can be suppressed by feeding CNS myelin proteins. Using immunohistochemistry and image analysis, the cellular immune response was quantified over the rostral-caudal axis of the spinal cord in rats with EAE and in animals fed high- or low-dose myelin basic protein (MBP) prior to inducing EAE (tolerized animals). In a subset of rats, MBP was fed 9 days after MBP immunization to examine the effect of oral tolerance on the progression of CNS pathology. In unfed rats or rats fed vehicle only, activated microglia and macrophages were co-localized with T-lymphocytes throughout the spinal cord, but greater cellular reactions were evident in gray matter relative to white matter. In all tolerized animals, the CNS inflammatory response was reduced relative to controls. Subtle pathologic changes were occasionally observed in the CNS of MBP-fed animals, but the distribution of inflammatory cells in the dorso-ventral axis was more polarized in animals fed high-dose MBP. In this group, more T-cells and activated microglia were present in the dorsal spinal cord, specifically in the gray matter. In the group fed MBP after disease induction, clinical disease progressed as in control non-fed rats, but recovery from disease appeared to be accelerated. Thus, the results presented here provide a comprehensive analysis of the distribution and magnitude of inflammatory cells within the spinal cord in EAE and challenge the theory that MBP-induced EAE is only a white matter disease. These data also describe how the activation and distribution of immune effector cells is altered by oral tolerance and may help predict a range of neurological deficits not previously appreciated in EAE, particularly those effected by gray matter pathology.

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

Chronic relapsing experimental autoimmune encephalomyelitis (EAE), induced in mice by the injection of myelin basic protein (MBP), is a T cell-mediated autoimmune disease characterized by periods of paralysis and remission. We have shown previously that the oral administration of MBP or MBP peptides renders Lewis rats refractory to EAE. This study was undertaken to examine the conditions necessary to produce oral tolerance in a chronic relapsing model of EAE in B10.PL mice. The optimal tolerizing regimen for the mouse was found to be a single feeding of 20 mg of MBP suspended in PBS. To determine the ability to suppress chronic disease, a range of doses (0.4-100 mg) was administered orally in a single dose before challenge. Larger oral doses (20 or 100 mg) of MBP provided the best protection from EAE, while 0.4 mg exacerbated the clinical course of disease. Secretion of the proinflammatory cytokines, IL-2 and IFN-gamma, were lowest in the group fed 20 mg. A single feeding of MBP before challenge or as late as the first day of clinical signs showed significant protection over the relapsing disease course. Once relapsing EAE was established, multiple oral doses of MBP were required to achieve suppression of clinical signs of disease. These findings suggest that vehicle, dosage, and timing are important considerations in the successful application of oral tolerance strategies for suppression of chronic disease processes.

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

Chronic relapsing experimental autoimmune encephalomyelitis (EAE), induced in mice by the injection of myelin basic protein (MBP), is a T cell-mediated autoimmune disease characterized by periods of paralysis and remission. We have shown previously that the oral administration of MBP or MBP peptides renders Lewis rats refractory to EAE. This study was undertaken to examine the conditions necessary to produce oral tolerance in a chronic relapsing model of EAE in B10.PL mice. The optimal tolerizing regimen for the mouse was found to be a single feeding of 20 mg of MBP suspended in PBS. To determine the ability to suppress chronic disease, a range of doses (0.4-100 mg) was administered orally in a single dose before challenge. Larger oral doses (20 or 100 mg) of MBP provided the best protection from EAE, while 0.4 mg exacerbated the clinical course of disease. Secretion of the proinflammatory cytokines, IL-2 and IFN-gamma, were lowest in the group fed 20 mg. A single feeding of MBP before challenge or as late as the first day of clinical signs showed significant protection over the relapsing disease course. Once relapsing EAE was established, multiple oral doses of MBP were required to achieve suppression of clinical signs of disease. These findings suggest that vehicle, dosage, and timing are important considerations in the successful application of oral tolerance strategies for suppression of chronic disease processes.

Treatment of autoimmune disease by oral tolerance to autoantigens

Multiple sclerosis (MS) is a chronic demyelinating disease of the human central nervous system (CNS) which can be characterized clinically by a remitting-relapsing or a chronic progressive course. There is a striking similarity between the clinical and histopathological features of MS and the experimentally induced disease, experimental autoimmune encephalomyelitis (EAE). Induced by the injection of myelin basic protein (MBP) and adjuvants, EAE is characterized by clinical neurologic signs of paralysis and histopathologic changes consisting of perivascular mononuclear infiltration and demyelination. We have reported that the oral administration of MBP exerts a profoundly suppressive effect on EAE induced in the Lewis rat. This MBP-induced oral tolerance is characterized by an inhibition of EAE clinical neurologic signs, reduced CNS histopathologic changes, a profound decrease in the T-lymphocyte proliferative response specific for the fed antigen, and a decrease in serum antibody specific for MBP. In a chronic relapsing model of EAE in the B10.PL mouse, we have shown that the oral administration of MBP either prior to MBP challenge or on the first day of clinical signs results in a decreased number and severity of EAE relapses. The oral tolerance approach has also proven effective in the suppression of other organ-specific autoimmune diseases including collagen-induced arthritis, adjuvant arthritis, uveoretinitis, experimental myasthenia gravis, diabetes, and thyroiditis as well as graft rejection. Two primary mechanisms have been proposed to explain oral tolerance in EAE-active suppression following feeding of lower doses of antigen and clonal anergy or deletion following administration of higher doses. In vivo approaches in rats and transgenic mice have been used to further explore the mechanisms underlying oral tolerance. Administration of recombinant interleukin (IL)-2 was shown to reverse the tolerance induced by feeding low doses of MBP, but not the tolerance induced by feeding high doses of MBP, indicating that deletion had occurred in the high-dose group. Moreover, the oral administration of MBP to MBP-specific T-cell receptor (TCR) transgenic mice resulted in a profound decrease of the transgenic T cells in the blood, lymph node cells (LNC), mesenteric LNC, and spleen compartments. The proliferative response to MBP was also profoundly reduced in these organs, indicating that the cells had been deleted from these sites. The results achieved in animal models have led to clinical trials of oral tolerization in three human autoimmune diseases--MS, uveoretinitis, and rheumatoid arthritis--with promising results.

Concept of autoimmunity following spinal cord injury: possible roles for T lymphocytes in the traumatized central nervous system

The effect of immunological activation on the neuropathologic sequelae and neurologic outcome from spinal cord injury is unclear. Similar to models of neuroinflammatory disease (e.g., experimental autoimmune encephalomyelitis; EAE), injury to the spinal cord precipitates the activation of resident microglia and the recruitment of circulating inflammatory cells (e.g., macrophages and lymphocytes). In EAE, these cells are known to cause tissue damage and loss of neurological function via autoimmune reactions to myelin proteins. The role these cells play in the pathology of traumatic injury to the spinal cord has not been clarified. In this review, data are presented that indicate that T cells isolated from spinal-injured rats are capable of causing neurologic deficits and histopathologic changes similar to EAE when injected intravenously into naive animals. These data are consistent with the concept of trauma-induced autoimmune reactions. However, disease transfer was only possible when T cells were obtained from animals at 1 week post-injury. Thus, the encephalitogenic T-cell repertoire appears to be rapidly regulated. It is possible that trauma-induced autoimmunity evolves into a mechanism by which the autoreactive repertoire regulates ongoing central nervous system (CNS) immunologic responses. Similar immunoregulatory networks have been proposed in EAE and are discussed here in the context of CNS trauma and neurodegenerative disease.

Oral tolerance in EAE: reversal of tolerance by T helper cell cytokines

Oral administration of myelin basic protein (MBP) inhibits clinical and histopathological manifestations of experimental autoimmune encephalomyelitis (EAE), but only partially reduces serum anti-MBP antibody titers. We report here that orally administered MBP alters the isotypic distribution of anti-MBP antibody-forming cells (AFC) among various lymphoid tissues, with the most profound differences seen in mucosal tissues. We observed an isotype-selective reduction in anti-MBP IgA but not IgM AFC frequencies in Peyer's patches. The anti-MBP IgA AFC frequencies could be reconstituted by addition of interleukin 4 (IL-4) and interleukin 5(IL-5). The cytokines did not appear to generate de novo responses since no increases in anti-MBP lgA AFC frequencies were observed in control cultures. These results indicate that decreased antibody production, as a result of oral antigen administration, can be reversed by exposure to the appropriate cytokines.

Oral tolerance in experimental autoimmune encephalomyelitis

In work performed by a number of laboratories, it has become quite clear that the oral administration of autoantigens exerts a profoundly suppressive effect on the development and long-term clinical course of autoimmune disease. Specific peptide sequences derived from the autoantigens are similarly suppressive. An interesting sidelight to emerge from specificity studies is that oral administration of a self-protein or peptide sequence (i.e., rat MBP peptide administered to a rat) is markedly less tolerogenic than oral administration of a non-self or even closely related sequence (guinea pig MBP peptide administered to a rat). The dose of oral antigen is now known to play a critical role in determination of the mechanism of oral tolerance, with low doses of antigen causing active suppression with concomitant release of TGFbeta1. Studies outlined here suggest that oral administration of higher antigen doses (e.g., 20 mg MBP to rats or mice) results in deletion of specific antigen-reactive T lymphocytes. This conclusion stems from the fact that injections of IL-2 could not reverse high-dose tolerance while reversing low-dose oral tolerance. Moreover, feeding MBP to MBP-TCR transgenic mice caused trafficking of transgenic cells to the intestine followed by a profound depletion of transgene-positive cells and reduction in proliferative function in all peripheral lymphoid organs. Oral tolerance has proven to be of therapeutic benefit in other animal models of autoimmune disease as well, including uveitis, collagen-induced arthritis, adjuvant arthritis, thyroiditis, myasthenia gravis, and diabetes. Initial human trials in multiple sclerosis, rheumatoid arthritis, and uveitis show promising results.

Exquisite peptide specificity of oral tolerance in experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE), induced in Lewis rats by injection of myelin basic protein (MBP) and adjuvant, is a T cell-mediated autoimmune disease. Earlier studies from our laboratory have shown that oral administration of guinea pig MBP before encephalitogenic challenge induces T cell anergy and results in the suppression of clinical signs and CNS histopathologic changes of EAE. In contrast, oral administration of rat MBP did not confer a similar degree of protection. This study was undertaken to determine the tolerogenicity of the synthetic peptide 68-88 derived from guinea pig (GP) MBP and rat MBP. These peptides differ by a single amino acid at position 80. Lewis rats fed GP 68-88 were protected from EAE induced with GP 68-88 or rat 68-88. In contrast, feeding rats 68-88 did not protect the animals from challenge with either peptide. Measurement of the frequency of peptide-reactive Th1 cells showed results consistent with the clinical picture. The in vitro proliferative response was significantly suppressed following oral administration of either whole GP MBP, the GP peptide, or the rat peptide, irrespective of clinical status. These results extend our earlier observation at the whole molecule level that GP but not rat MBP confers oral tolerance. These findings suggest that small structural differences at the amino acid level can produce dramatic differences in clinical outcome, with important implications for the design of multiple sclerosis clinical trials.

Exquisite peptide specificity of oral tolerance in experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE), induced in Lewis rats by injection of myelin basic protein (MBP) and adjuvant, is a T cell-mediated autoimmune disease. Earlier studies from our laboratory have shown that oral administration of guinea pig MBP before encephalitogenic challenge induces T cell anergy and results in the suppression of clinical signs and CNS histopathologic changes of EAE. In contrast, oral administration of rat MBP did not confer a similar degree of protection. This study was undertaken to determine the tolerogenicity of the synthetic peptide 68-88 derived from guinea pig (GP) MBP and rat MBP. These peptides differ by a single amino acid at position 80. Lewis rats fed GP 68-88 were protected from EAE induced with GP 68-88 or rat 68-88. In contrast, feeding rats 68-88 did not protect the animals from challenge with either peptide. Measurement of the frequency of peptide-reactive Th1 cells showed results consistent with the clinical picture. The in vitro proliferative response was significantly suppressed following oral administration of either whole GP MBP, the GP peptide, or the rat peptide, irrespective of clinical status. These results extend our earlier observation at the whole molecule level that GP but not rat MBP confers oral tolerance. These findings suggest that small structural differences at the amino acid level can produce dramatic differences in clinical outcome, with important implications for the design of multiple sclerosis clinical trials.

Rat peritoneal mast cells present antigen to a PPD-specific T cell line

Rat peritoneal mast cells were examined to determine whether mast cells can stimulate T cell proliferation through antigen presentation. Mast cells were obtained by peritoneal lavage and purified to 98% using density gradient centrifugation. Purified peritoneal mast cells expressed MHC class II molecules as determined by flow cytometry using monoclonal antibody OX6 specific for common determinants of rat class II. The intensity of class II expression by mast cells was not significantly increased upon incubation with recombinant rat IFN-gamma. Peritoneal mast cells also were found to express the accessory molecules ICAM-1 (CD54) and LFA-1 beta (CD18) but not LFA-1 alpha (CD11a). In the presence of antigen, purified mast cells stimulated proliferation of an autologous CD4+, PPD-specific T cell line. This stimulation was blocked by OX6 antibody, confirming that the proliferation was class II dependent. T cell proliferation was similarly induced by purified mast cell populations that were completely monocyte and macrophages depleted. These results demonstrate that mast cells, through their expression of MHC class II and accessory molecules, are capable of antigen presentation.

Neuropsychological performance and CD4 levels in HIV-1 asymptomatic infection

The performance of 68 HIV-1 seropositive asymptomatic (HIV+) subjects stratified on CD4 levels were compared with 82 HIV-1 seronegative (HIV-) subjects on a battery of neuropsychological, mood state, and perceived health status measures. The neuropsychological test battery included measures of attention, reaction time, memory, intellectual ability, psychomotor speed, frontal lobe or "executive" function, and decision time. None of the HIV+ subjects were taking antiviral agents. The groups did not differ for age, mood state, or WAIS-R Verbal and Performance IQ scores. Due to group differences for education and weekly ethanol consumption, both variables were used as covariates in multivariate analyses of variance. Relatively few differences were observed between subgroups of HIV+ patients or between these subgroups and control subjects. These data suggest that factors other than absolute levels of immunosuppression as expressed by CD4 levels alone, appear to be responsible for the deficits observed in HIV+ asymptomatic patients.

Duration of illness and neuropsychological performance in asymptomatic HIV infection

The relationship between duration of illness and neuropsychological performance was examined in 25 asymptomatic HIV-infected men with an estimated date of seroconversion. Mean duration of illness was approximately 2 years. After controlling for CD4 level at the time of neuropsychological examination, duration of illness was correlated with measures of visual attention, mental flexibility, dexterity, auditory information processing, and response fluency, as well as an overall measure of neuropsychological performance. Although these patients performed within normal limits, these data suggest that duration of infection may be related to subtle alterations in neuropsychological performance. These results are discussed with regard to possible mechanisms that implicate gradual accumulation of neurotoxins.

Change in neuropsychological performance in asymptomatic HIV infection: 1-year follow-up

OBJECTIVE

To examine the stability of cognitive function in patients with asymptomatic HIV infection.

DESIGN

Previous longitudinal studies of cognitive function have focused on patients who progress in terms of disease stage. The present study avoided this potential confounding factor by including only subjects who remained in the asymptomatic stage of infection over the follow-up period.

METHOD

Subjects were administered an extensive neuropsychological test battery at baseline and 1 year follow-up. Overall performance was characterized as normal or abnormal based on the performance of a well-matched HIV-negative control group.

RESULTS

A significantly higher proportion of HIV-positive subjects became abnormal at the follow-up examination. Comparison of the seropositive subjects who remained normal with those who became abnormal revealed no differences at baseline on age, education, depression or CD4 levels. Subjects who became abnormal had worse performance at baseline on measures of information processing, verbal learning and memory, and reaction time.

CONCLUSIONS

These data indicate that cognitive function may decline in some patients who continue to be in the asymptomatic stage of infection. Patients with a pattern of cognitive abnormalities at baseline, which includes information processing and reaction time deficits, may be at increased risk for declines in function during early stages of infection.

Depression and neuropsychological performance in asymptomatic HIV infection

OBJECTIVE

The authors examined the effect of depression on neuropsychological performance in HIV-infected men. Previous studies have suggested that depression may account for the neuropsychological abnormalities observed in some patients with HIV infection, but few studies have specifically examined this question.

METHOD

An extensive neuropsychological test battery was administered to 121 HIV-seropositive asymptomatic men and 42 HIV-seronegative comparison subjects. The seropositive subjects were grouped into depressed and non-depressed groups on the basis of scores on the Beck Depression Inventory, Hamilton Rating Scale for Depression, and Structured Clinical Interview for DSM-III-R.

RESULTS

Statistical comparisons revealed very few measures on which the depressed seropositive subjects scored significantly worse than either of the nondepressed comparison groups. The nondepressed seropositive group differed consistently from the seronegative comparison subjects on measures of verbal memory and dexterity.

CONCLUSIONS

These data indicate that the subtle neuropsychological abnormalities observed in some asymptomatic HIV-seropositive subjects cannot be attributed to depression. These data also indicate the advantages of a multifaceted approach to assessment of depression.

Suppression of experimental autoimmune encephalomyelitis by restraint stress: sex differences

We have recently reported that female Lewis rats exhibit significantly higher basal circadian levels of corticosterone (Cort) than male Lewis rats. The studies reported here were designed to explore whether male and female Lewis rats demonstrate a differential suppression of experimental autoimmune encephalomyelitis (EAE) following exposure to an identical regimen of repetitive restraint stress. Rats were restrained for 1 or 9 h/day beginning 5 days before myelin basic protein (MBP) challenge and extending through the recovery period (18 days post challenge). Both clinical signs and histopathological changes of EAE were more significantly suppressed in 9-h-stressed females relative to male Lewis rats. Investigation of the mechanism underlying the stress-induced suppression of EAE revealed that restraint stress did not alter the clinical course of EAE in rats challenged with MBP 68-88 encephalitogenic peptide, suggesting that restraint stress may affect processing and/or presentation of the MBP molecule. Stressed rats exhibited decreased interleukin-2 and interferon gamma production, and the frequency of MBP-reactive lymphocytes was reduced in comparison to non-stressed rats. Finally, repetitive restraint stress had no effect on blood-spinal cord permeability during EAE. The results presented here underscore the importance of such experimental variables as sex, strain, time of day, and the kinetics of immune response development.

Neuropsychological performance in symptomatic and asymptomatic HIV infection

OBJECTIVE

To examine cognitive function in patients at various stages of HIV infection, and to determine the nature and severity associated with stage of illness.

DESIGN

Subjects were administered an extensive battery of neuropsychological tests.

SUBJECTS

Two hundred and thirty-three HIV-1-infected homosexual/bisexual men and 77 HIV-negative control subjects who had been screened for previous neurological illness. All subjects were volunteers in a longitudinal study of neurobehavioral complications of HIV infection.

RESULTS

Patients with symptomatic infection differed from controls on a large number of measures, and asymptomatic patients had a more circumscribed pattern of deficit. On a summary measure of cognitive impairment, there was a twofold increase in the prevalence of impairment in asymptomatic patients relative to controls, and a fourfold increase in symptomatic patients. Memory and dexterity problems appear to be early features of neurobehavioral dysfunction, and frontal lobe deficits were found in patients with symptomatic infection.

CONCLUSION

These data indicate that there is a steady increase in the prevalence of neurobehavioral abnormalities associated with stage of infection. The pattern of abnormality also varies with disease stage.

Drug and alcohol use and neuropsychological performance in asymptomatic HIV infection

The effect of drug and alcohol abuse on neuropsychological performance was examined in 132 human immunodeficiency virus-seropositive gay or bisexual men. Syndromal (diagnostic) criteria of alcohol/drug abuse based on DSM-III-R were used, and quantitative estimates of alcohol consumption were obtained. Very few differences appeared between substance abuse subgroups formed on the basis of recency or severity of drug use. There were some correlations with the quantitative estimate of alcohol use, but not on the measures previously found to differentiate seronegative and asymptomatic seropositive gay men. These data indicate that alcohol use does affect neuropsychological performance but does not account for the differences observed in studies of seronegative and seropositive subjects.

MR of head and neck adenopathy in asymptomatic HIV-seropositive men

PURPOSE

Adenopathy is a well-known component of AIDS-related complex. Our goal was to determine whether asymptomatic HIV-infected persons have characteristic findings of head and neck adenopathy on MR imaging and whether there is an association between the MR findings and the CD4 lymphocyte counts.

METHODS

We blindly and retrospectively evaluated the distribution and size of lymphadenopathy seen on screening MR examinations that were performed on 50 asymptomatic HIV-positive male subjects and 50 age-matched HIV-negative control subjects. We also correlated the imaging findings in HIV-seropositive and -seronegative subjects with their CD4 counts.

RESULTS

The HIV-positive subjects had a higher incidence of adenopathy compared with the controls. Statistically significant differences were found between the groups in size and number of neck lymph nodes, thickness of the adenoids, size of high, deep cervical-retropharyngeal lymph nodes, and presence of parotid abnormalities. We found a correlation between increasing lymph node size and decreasing CD4 levels.

CONCLUSION

We conclude that HIV-positive asymptomatic patients have a high incidence of head and neck abnormalities including lymphadenopathy, and alteration in their CD4 counts not commonly seen in seronegative control subjects.

Quantitation of antigen-specific immune responses in human immunodeficiency virus (HIV)-infected individuals by limiting dilution analysis

The lymphocyte proliferative response to recall antigens is lost following HIV infection. We sought to devise a means by which the functional immune status of persons in the early stages of HIV infection could be monitored quantitatively. The response to tetanus toxoid was examined in 45 HIV-infected individuals and 11 controls using conventional lymphocyte proliferative assays concurrently with limiting dilution analysis utilizing the secretion of interleukin-2 as the measure of a response. Our data show that the limiting dilution analysis detects tetanus toxoid-reactive T cells in 80% of those tested, as compared to only 44% by proliferation. However, the frequency of tetanus-reactive T cells in HIV-infected individuals (median frequency = 1/59,156) is decreased five-fold as compared to seronegative controls (median frequency = 1/11,599). Longitudinal studies demonstrated a time-dependent decrease in the frequency of tetanus-specific T cell responses in the HIV-infected individuals. Thus, the limiting dilution analysis is a quantitative approach for detecting antigen-specific T cells in HIV-infected individuals, and may be used to monitor changes in T cell function in HIV infection.

Sex and strain differences in the circadian rhythm fluctuation of endocrine and immune function in the rat: implications for rodent models of autoimmune disease

This study compares 24-h basal patterns of corticosterone and immunoreactivity for Lewis and Fischer (F344) strain rats. Significant differences in the circadian rhythm of plasma corticosterone were found across sex and strain. Male Lewis rats exhibited significantly lower 24-h corticosterone levels relative to female Lewis and male F344 rats. In addition, male Lewis rats were found to have higher mononuclear cell counts than female Lewis or male F344 rats, particularly in the peripheral blood and spleen compartments. Levels of CD4-bearing lymphocytes in blood, lymph node, and spleen were found to be higher in Lewis rats compared to the F344 strain over a 24-h period. In general, percentages of CD8- and major histocompatibility complex (MHC) class II-bearing lymphocytes were shown to vary over 24 h in all compartments across strains. Given that the Lewis rat has low basal levels of circulating corticosterone, and comparatively higher numbers of CD4-bearing lymphocytes, these factors may play a causative role in the known susceptibility of this strain to many experimental models of autoimmune disease.

Oral tolerance in experimental autoimmune encephalomyelitis. III. Evidence for clonal anergy

We have recently reported that experimental autoimmune encephalomyelitis (EAE) can be suppressed by the oral administration of myelin basic protein (MBP). The oral introduction of 20 mg MBP together with a trypsin inhibitor results in inhibition of EAE clinical signs, decreased CNS histopathologic changes and dramatically reduced MBP-specific proliferative responses in fed and challenged Lewis rats. In the present study, we have investigated the mechanism underlying MBP-induced oral tolerance in EAE. Neither lymphoid cells (lymph node cells, spleen cells, Peyer's patch lymphocytes, thymocytes) nor humoral elements derived from tolerant donors were capable of transferring the tolerance to naive recipients. Moreover, lymphoid cells obtained from orally tolerant donors exhibited a marked decrease in their capacity to transfer EAE to naive recipient rats, even after in vitro activation with MBP or Con A. We observed that EAE could be readily transferred into orally tolerant rats using MBP-specific encephalitogenic T cell lines. In vitro cell mixing studies showed that the proliferation of lymphocytes from MBP-sensitized donors was not inhibited by the addition of lymphoid cells from tolerant donors, arguing against the role of a suppressor cell. Investigation of MBP-stimulated lymphokine production showed that both IL-2 and IFN-gamma levels were substantially decreased in spleen and lymph node cell cultures from MBP-fed rats compared to vehicle-fed control animals. Furthermore, limiting dilution analyses revealed that MBP-fed rats exhibited a profound decrease in MBP-reactive, IL-2-secreting lymphocytes relative to control animals. Thus, because lymphocytes from MBP-fed rats neither proliferate nor secrete IL-2 or IFN-gamma in response to MBP and we can find no compelling evidence for the role of suppressor cells, we propose that the oral administration of MBP results in a state of clonal anergy.

Oral tolerance in experimental autoimmune encephalomyelitis. III. Evidence for clonal anergy

We have recently reported that experimental autoimmune encephalomyelitis (EAE) can be suppressed by the oral administration of myelin basic protein (MBP). The oral introduction of 20 mg MBP together with a trypsin inhibitor results in inhibition of EAE clinical signs, decreased CNS histopathologic changes and dramatically reduced MBP-specific proliferative responses in fed and challenged Lewis rats. In the present study, we have investigated the mechanism underlying MBP-induced oral tolerance in EAE. Neither lymphoid cells (lymph node cells, spleen cells, Peyer's patch lymphocytes, thymocytes) nor humoral elements derived from tolerant donors were capable of transferring the tolerance to naive recipients. Moreover, lymphoid cells obtained from orally tolerant donors exhibited a marked decrease in their capacity to transfer EAE to naive recipient rats, even after in vitro activation with MBP or Con A. We observed that EAE could be readily transferred into orally tolerant rats using MBP-specific encephalitogenic T cell lines. In vitro cell mixing studies showed that the proliferation of lymphocytes from MBP-sensitized donors was not inhibited by the addition of lymphoid cells from tolerant donors, arguing against the role of a suppressor cell. Investigation of MBP-stimulated lymphokine production showed that both IL-2 and IFN-gamma levels were substantially decreased in spleen and lymph node cell cultures from MBP-fed rats compared to vehicle-fed control animals. Furthermore, limiting dilution analyses revealed that MBP-fed rats exhibited a profound decrease in MBP-reactive, IL-2-secreting lymphocytes relative to control animals. Thus, because lymphocytes from MBP-fed rats neither proliferate nor secrete IL-2 or IFN-gamma in response to MBP and we can find no compelling evidence for the role of suppressor cells, we propose that the oral administration of MBP results in a state of clonal anergy.

Rate of CD4 decline and neuropsychological performance in HIV infection

This study examined the relationship between performance on a battery of neuropsychologic tasks and rate of CD4 lymphocyte decline in 47 gay or bisexual men infected with the human immunodeficiency virus type 1. Subjects were volunteers for a longitudinal study of the human immunodeficiency virus infection and were not selected because of neuropsychiatric symptoms. Subjects were at all stages of illness, although most were asymptomatic. Faster rates of decline in percent CD4 lymphocyte were related to poorer performance on measures of memory and reaction time. This relationship was independent of stage of illness and CD4 level at the time of neuropsychologic examination, and was not due to medication effects. The rate of percent CD4 lymphocyte cell loss is associated with and may represent a risk factor for the development of the human immunodeficiency virus-related neurobehavioral deficit.

Facilitation of dimethylbenz[a]anthracene-induced rat mammary tumorigenesis by restraint stress: role of beta-endorphin, prolactin and naltrexone

In order to investigate the involvement of opioid peptides and prolactin in stress-facilitated mammary cancer, we studied the effect of chronic restraint stress on dimethylbenz[a]-anthracene (DMBA)-induced mammary tumorigenesis and the effect of an opiate antagonist, naltrexone, on this process. Female Fischer-344 rats (n = 160) were administered 15 mg DMBA/ml of sesame oil/rat by intragastric intubation. Eighty rats were subjected to daily 30 min restraint stress in a plastic cylinder, and 80 rats served as control not subjected to the stressor. Half of the rats from each group received naltrexone (1 mg/kg, i.p. daily). Five rats from each group (restraint stress +/- naltrexone and control +/- naltrexone) were killed every 2-3 weeks. Rats subjected to restraint stress developed a greater number of tumors earlier. Naltrexone decreased the tumor incidence in the stressed animals from 32 to 12% (P less than 0.001) and in unstressed rats from 27 to 15% (P less than 0.001) at the end of 18 weeks. Stressed rats showed a decrease of 48% (P less than 0.001) in the level of hypothalamic beta-endorphin. Plasma prolactin increased from 4-13 ng/ml in the control rats to 109-396 ng/ml (P less than 0.001) in the stressed rats throughout the 18 week period. The beneficial effect of naltrexone was associated with 42% (P less than 0.01) increase in T cell proliferation, but greater than 90% (P less than 0.001) decrease in plasma prolactin level was observed in naltrexone-treated rats compared to the untreated animals. Rats subjected to restraint stress showed a 15% (P less than 0.001) decrease in weight gain at the end of the experiment (18 weeks). Neither restraint stress nor naltrexone administration affected the caloric intake of rats during this period. Thus, we believe that restraint stress facilitates DMBA-induced mammary tumors by releasing beta-endorphin and prolactin, and naltrexone shows a beneficial effect by opposing the effect of beta-endorphin on prolactin release in the stressed animals.

Oral tolerance in experimental autoimmune encephalomyelitis: serum and salivary antibody responses

We have recently reported that the oral administration of myelin basic protein (MBP) prior to encephalitogenic challenge results in suppression of experimental autoimmune encephalomyelitis (EAE). We examined the serum and salivary antibody responses to MBP in orally tolerant rats using an avidin-biotin enzyme-linked immunosorbent assay. Serum anti-MBP IgA and IgG, but not IgM levels are suppressed in orally tolerant versus control rats. This suppression is time dependent and is confined to the period when animals would otherwise be manifesting EAE clinical signs. In contrast, there is an increase in salivary anti-MBP IgA levels in MBP-fed rats relative to vehicle-fed controls. Thus, MBP-induced unresponsiveness is demonstrable at the humoral level, and moreover, a discrete compartmentalization between the serum and salivary anti-MBP responses exists.

Genetic resistance in experimental autoimmune encephalomyelitis. I. Analysis of the mechanism of LeR resistance using radiation chimeras

Experimental autoimmune encephalomyelitis (EAE) is a cell-mediated autoimmune disease of the central nervous system that has been extensively studied in the rat. The Lewis rat is highly susceptible to the induction of EAE, while the Lewis resistant (LeR) rat is known to be resistant. In this paper, we demonstrate that the LeR rat, which was derived from the Lewis strain by inbreeding of fully resistant animals, is histocompatible with the Lewis strain. Radiation chimeras, a tool for distinguishing between immunologic and nonimmunologic resistance mechanisms, were utilized to analyze the cellular mechanisms involved in genetic resistance to EAE. By transplanting bone marrow cells from LeR rats into irradiated Lewis recipients, Lewis rats were rendered resistant to EAE induction. Likewise, transplanting Lewis bone marrow cells into irradiated LeR recipients rendered LeR rats susceptible. Mixed lymphoid cell chimeras using bone marrow, spleen, and thymus cells in Lewis recipient rats revealed individual lymphoid cell types and cell interactions that significantly affected the incidence and severity of EAE. Our results suggest that LeR resistance is mediated by hematopoietic/immune cells, and that cells located in the spleen appear to play a critical role in the resistance/susceptibility to EAE induction. Depletion of splenic adherent cells did not change the patterns of EAE resistance. In vivo cell mixing studies suggested the presence of a suppressor cell population in the LeR spleen preparations which exerted an inhibitory effect on Lewis autoimmune responses. Thus, the mechanism of LeR resistance appears to be different from that in other EAE-resistant animals.

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.

Gangliosides suppress the proliferation of autoreactive cells in experimental allergic encephalomyelitis: ganglioside effects on IL-2 activity

Gangliosides have been shown to suppress human and murine lymphocyte proliferative responses in vitro. We tested the suppressive effects of gangliosides on the proliferation of autoreactive lymphoid cells obtained from Lewis rats with experimental allergic encephalomyelitis (EAE). Exogenous rat brain gangliosides inhibited both antigen- and mitogen-induced proliferation by as much as 79 and 93%, respectively. Gangliosides similarly inhibited the antigen-induced proliferation of a myelin basic protein (MBP)-reactive T-cell line which is able to passively induce EAE. Suppression was greatest when gangliosides were added at the initiation of culture, and was not abrogated by supraoptimal antigen concentration. Interleukin 2 (IL-2) activity in culture supernatants was not diminished by the addition of gangliosides. Gangliosides did not inhibit the IL-2-induced proliferation of a murine IL-2-dependent cell line, CTLL-20, unless the IL-2 was first preincubated with gangliosides before the addition of CTLL-20. Preincubation of CTLL-20 with gangliosides resulted in no inhibition of the subsequent responses to IL-2. Exogenous gangliosides did not decrease the binding of a monoclonal antibody directed against the rat cell surface IL-2 receptor. Addition of exogenous IL-2 to ganglioside-suppressed cultures had no effect or only partially restored the proliferative responses. Therefore, gangliosides were shown to inhibit the proliferation of autoreactive lymphoid cells without affecting IL-2 production or IL-2 receptor expression.

Modification of the clinical and histopathologic expression of experimental allergic encephalomyelitis by the vasoactive amine antagonist cyproheptadine

Experimental allergic encephalomyelitis (EAE) is an autoimmune syndrome that can be induced in Lewis rats by myelin basic protein (BP) in complete Freund's adjuvant (CFA). Rats that have recovered from a primary episode of EAE display paradoxical long-term resistance to EAE reinduction by BP-CFA. Previous observations indicated, however, that clinical disease could be reinduced in convalescent rats by a concomitant secondary challenge with BP-CFA + Bordetella pertussis extract (PERT). Vascular permeability changes in the central nervous system (CNS) paralleled disease reinduction. To further probe the relationship between disease reinduction and vascular permeability, convalescent rats were treated with the vasoactive amine antagonist cyproheptadine (CYP) prior to a secondary challenge with BP-CFA + PERT. Data presented here indicate that CYP treatment results in substantial protection of convalescent rats from clinical disease reinduction by BP-CFA + PERT. CYP did not, however, prevent the development of new CNS lesions. CYP therapy also altered the clinical course of EAE induced by a primary injection of BP-CFA + PERT. In these rats, there was a delay in the onset of clinical signs as well as in the appearance of CNS lesions. Nevertheless, both CYP-treated and untreated naive rats challenged with BP-CFA + PERT eventually developed severe and usually lethal EAE. The effect of CYP on EAE induced in naive rats without including PERT in the sensitization protocol was also evaluated. In contrast to the mitigating effect of CYP on EAE induced or reinduced by BP-CFA + PERT, CYP treatment did not affect the clinical course or the development of CNS lesions in rats challenged with BP-CFA alone. Likewise, the passive transfer of EAE, mediated by mitogen-stimulated cells obtained from BP-CFA-sensitized donors, was not affected by CYP treatment. Collectively, these data indicate that CYP therapy altered the expression of EAE induced by regimens that included PERT, but did not affect EAE induced without PERT. In view of the opposing effects of PERT and CYP on vascular permeability, these data are consistent with the hypothesis that alterations in vascular permeability may play a crucial role in controlling the expression of autoimmune neurological diseases.

Species-restriction of rat lymphoid cell migration inhibitory factor

Migration inhibitory factor (MIF) was produced by lymphoid cells of Lewis rats in response to infection with Bacille Calmette Guérin (BCG), mixed lymphocyte reaction or concanavalin A stimulation. It was found that rat lymphokine-containing supernatants demonstrate a definite species specificity, in that MIF activity is observed only when rat indicator cells and not when guinea-pig indicator cells are used. A comparative study of MIF activities, using rat peritoneal exudate cells, revealed that all three methods stimulated MIF production by either spleen or lymph node cells. Only infection with BCG induced peripheral blood leukocytes to elaborate MIF. In all cases, rat MIF inhibited rat peritoneal exudate cells but not guinea-pig peritoneal exudate cells. Possible explanations for the species specificity of rat MIF including a role for receptor carbohydrate moieties and fibronectin are discussed.

Oligoclonal IgG in rabbits with experimental allergic encephalomyelitis: non-reactivity of the bands with sensitizing neural antigens

Oligoclonal IgG bands have recently been reported to occur in cerebrospinal fluid (CSF) and serum of rabbits with experimental allergic encephalomyelitis (EAE). To examine the specificity of these bands, a) individual bands eluted from rabbit CSF and sera were tested by radioimmunoassay (RIA) for anti-MBP activity and b) rabbit sera were absorbed with the neuroantigens used for sensitization. RIA of eluates from sequential agar gel slices of the entire IgG region of serum or CSF from MBP sensitized rabbits showed that anti-MBP activity occurred throughout the IgG region and did not localize to specific band-containing fractions. Furthermore, there was no change in banding patterns following absorption of EAE rabbit sera with washed brain homogenates, soluble MBP or MBP conjugated to Sepharose beads. Therefore, our results indicate that the oligoclonal IgG response in EAE is not preferentially directed against the sensitizing neuroantigen, and we raise the possibility of nonspecific B cell activation.

Endogenous myelin basic protein-serum factors (MBP-SFs) and anti-MBP antibodies in humans. Occurrence in sera of clinically well subjects and patients with multiple sclerosis

Sera of normal subjects and patients wtih multiple sclerosis (MS) have been frequently found to contain picomolar quantities of endogenous myelin basic protein-serum factors (MBP-SFs). These serum factors, collectively representing a heterogeneous spectrum, were detected and measured by means of a competitive inhibition radioimmunoassay (RIA) designed to distinguish their respective binding affinities with anti-MBP reagent antiserum. Anti-MBP antibodies in these same normal and patient sera were also detected and their differing binding affinities determined. In general, when sera of normal subjects were found to contain free MBP-SFs, the reagent anti-MBP antibodies in the reagent antiserum used to detect them were of relatively high binding affinity (8 X 10(8) M-1). When normal sera were found to contain free anti-MBP antibodies, the affinities of such antibodies were invariably lower (0.06-0.7 X 10(8) M-1). In contrast, sera of patients with active MS and exhibiting clinical fluctuations in their disease, infrequently contained high or medium high affinity MBP-SFs, whereas higher affinity anti-MBP antibodies were commonly detected. These patterns of MBP-SFs and anti-MBP antibodies in normal and MS human sera resemble those previously observed in studies of normal Lewis rats and rats developing experimental allergic encephalomyelitis (EAE). The findings here reported provide additional support for the view that circulating endogenous MBP-SFs may function as neuroautotolerogens that restrict expansion of MBP-reactive lymphoid cell clones having potentially injurious effector activity for central nervous system (CNS) tissue.

Cerebrospinal fluid and serum oligoclonal IgG bands in rabbits with experiment allergic encephalomyelitis

Rabbits sensitized with whole nervous tissue or myelin basic protein (MBP) plus adjuvant and developing experimental allergic encephalomyelitis (EAE) were studied for the presence of oligoclonal immunoglobulin (Ig) bands in spinal fluid and serum. Samples obtained prior to sensitization and at the time of sacrifice were concentrated and subjected to agar gel electrophoresis. Of 11 rabbits receiving whole nervous tissue and developing severe clinical signs of EAE, 7 showed new oligoclonal Ig bands in spinal fluid and in serum obtained 19 days or more after sensitization. With MBP sensitization, 2 of 6 rabbits exhibited new spinal fluid bands, while all 6 rabbits studied demonstrated serum banding. The bands were identified as IgG by immunochemical studies using peroxidase-labeled antisera and by Staph. protein A absorption. The majority of animals showed no banding in presensitization samples. The finding of oligoclonal IgG in EAE reveals yet another immunologic correlation between EAE and the human demyelinating disease, multiple sclerosis.