Plaque-bearing mice with reduced levels of oligomeric amyloid-beta assemblies have intact memory function.

The amyloid-beta (Abeta) protein exists in the aging mammalian brain in diverse assembly states, including amyloid plaques and soluble Abeta oligomers. Both forms of Abeta have been shown to impair neuronal function, but their precise roles in Alzheimer's disease (AD) -associated memory loss remain unclear. Both types of Abeta are usually present at the same time in the brain, which has made it difficult to evaluate the effects of plaques and oligomers individually on memory function. Recently, a particular oligomeric Abeta assembly, Abeta 56, was found to impair memory function in the absence of amyloid plaques. Until now it has not been possible to determine the effects of plaques, in the absence of Abeta oligomers, on memory function. We have identified Tg2576 mice with plaques but markedly reduced levels of Abeta oligomers, which enabled us to study the effects of plaques alone on memory function. We found that animals with amyloid plaques have normal memory function throughout an episode of reduced Abeta oligomers, which occurs during a period of accelerated amyloid plaque formation. These observations support the importance of Abeta oligomers in memory loss and indicate that, at least initially, amyloid plaques do not impair memory.

Tau suppression in a neurodegenerative mouse model improves memory function.

Neurofibrillary tangles (NFTs) are the most common intraneuronal inclusion in the brains of patients with neurodegenerative diseases and have been implicated in mediating neuronal death and cognitive deficits. Here, we found that mice expressing a repressible human tau variant developed progressive age-related NFTs, neuronal loss, and behavioral impairments. After the suppression of transgenic tau, memory function recovered, and neuron numbers stabilized, but to our surprise, NFTs continued to accumulate. Thus, NFTs are not sufficient to cause cognitive decline or neuronal death in this model of tauopathy.

Immunity to heat shock proteins and neurological disorders of women.

Stress or heat shock proteins are constitutively expressed in normal CNS tissues in a variety of cell types (oligodendrocytes, astrocytes, and neurons). Their presence may protect cells from various stresses, such as hypoxia, anoxia, and excessive excitatory stimulation. Increased amounts of hsp are expressed in various cells of the CNS during acute toxic-metabolic states and in chronic degenerative and inflammatory diseases. Increased expression of hsp may lead to immune responses to these proteins. Antibodies to mycobacterial hsp bind to normal human myelin and to oligodendrocytes in regions of MS demyelination. Cellular immune responses to hsp occur with increased frequency and magnitude in persons with MS, especially those with recent onset of disease. In addition, there are populations of T cells expressing gamma/delta T cells in the brains and spinal fluids of persons with MS, suggesting an in situ immune response to hsps. Humoral immune responses to hsp are found in CSF, but no disease specificity has been documented. Some myelin proteins have sequence homology with particular hsps. One instance is the homology between a peptide of mycobacterial Hsp65 and the myelin protein CNP. Our data on EAE suggest that immune responses to either cross-reactive hsp epitopes or whole hsp can modify the course of both acute and chronic relapsing EAE. In addition, the severity and frequency of environmental exposure to infectious agents can modify the course of EAE, possibly by altering the patterns of immune response to hsp. Finally, tolerance to the small hsp, alpha B-crystallin, a putative autoantigen in persons with MS, alters the course of relapsing EAE, supporting its role in chronic, autoimmune CNS disease. Modifying immune responses to hsp may be a potential new treatment option for persons with MS.

Heat shock proteins and experimental autoimmune encephalomyelitis. II: environmental infection and extra-neuraxial inflammation alter the course of chronic relapsing encephalomyelitis.

We wished to study how infections might trigger relapses of autoimmune diseases such as multiple sclerosis (MS) and encephalomyelitis (EAE). We hypothesized that immune responses to heat shock proteins (hsp) induced by an infection could modulate responses to autoantigens. We induced extra-neuraxial inflammation in SJL mice housed either in specific-pathogen free (SPF) or conventional facilities. Mice in conventional housing are continuously exposed to large numbers of infectious agents. Spleen cell proliferative responses to human HSP60 and bacterial HSP65 were measured as were numbers of cells secreting IFN-gamma or IL-5. Proliferative responses to HSP60 were increased in conventionally housed mice compared to SPF mice and this was associated with skewing of secreted cytokines toward a Th2 pattern. Skewing toward a Th1 pattern was noted in SPF mice. Acute and relapsing EAE was induced in both groups of mice. Acute EAE was, in general, equivalent in all groups. However, SPF mice had more severe relapses than did conventionally housed animals and these differences were amplified by extra-neuraxial inflammation. Immunocytochemical analyses of brains from mice with relapsing EAE showed that increased numbers of brain gamma/delta cells were associated with disease remission. Our data suggest that frequent exposure to infectious agents leads to a relative Th2 skewing of immune responses to hsp and that this is associated with milder, less frequent relapses of EAE. They also support the concept that immune responses to hsp are of potential importance in exacerbating and perpetuating organ-restricted autoimmune diseases.

Heat shock or stress proteins and their role as autoantigens in multiple sclerosis.

Stress or heat shock proteins are constitutively expressed in normal CNS tissues, in a variety of cell types (oligodendrocytes, astrocytes, and neurons). Their presence may protect cells from various stresses, such as hypoxia, anoxia, and excessive excitatory stimulation. Increased amounts of hsp are expressed in various cells of the CNS during acute toxic-metabolic states and in chronic degenerative and inflammatory diseases. Increased expression of hsp may lead to immune responses to these proteins. Antibodies to mycobacterial hsp bind to normal human myelin and to oligodendrocytes in regions of MS demyelination. Cellular immune responses to hsp occur with increased frequency and magnitude in persons with MS, especially those with recent onset of disease. In addition, there are populations of T cells expressing gamma/delta antigen receptors in the brains and spinal fluids of persons with MS, suggesting an in situ immune response to hsp. Humoral immune responses to hsp are found in CSF, but no disease specificity has been documented. Some myelin proteins have sequence homology with particular hsp. One instance is the homology between a peptide of mycobacterial HSP 65 and the myelin protein CNP. Our data in EAE suggest that immune responses to either cross-reactive epitopes or whole hsp can modify the course of both acute and chronic relapsing EAE. These data support the hypothesis that an immune response to an infectious agent's hsp could result in a cross-reactive immune response to CNS myelin, or to responses to endogenous, CNS-expressed hsp, resulting in demyelination. This may be an important mechanism in the pathogenesis of MS.

Heat shock proteins and experimental autoimmune encephalomyelitis (EAE): I. Immunization with a peptide of the myelin protein 2',3' cyclic nucleotide 3' phosphodiesterase that is cross-reactive with a heat shock protein alters the course of EAE.

We describe sequence similarity and immunologic cross-reactivity between a peptide of the mycobacterial hsp, HSP65, and the myelin protein 2',3' cyclic nucleotide 3' phosphodiesterase (CNP). We demonstrate that immunization with the homologous cross-reactive CNP peptide (hsp-CNP peptide) has significant biological consequences. Rats immunized with hsp-CNP peptide in either complete Freund's adjuvant (CFA) or incomplete Freund's adjuvant (IFA) produce large amounts of peptide-specific antibody. Isotypes of antibodies in animals immunized with peptide in CFA are IgG1 and IgG2a. Isotypes of antibodies in rats immunized with peptide in IFA are predominantly IgG1, with low titers of IgG2a. T cell proliferative responses to HSP65 are present in rats immunized with peptide in CFA. T cell responses to HSP65 initially are absent in rats immunized with peptide in IFA but develop over time. T cell proliferative responses to hsp-CNP peptide were not detected. None of the groups of rats developed clinical or histologic evidence of experimental autoimmune encephalomyelitis (EAE). To induce EAE, rats preimmunized with hsp-CNP peptide were challenged with guinea pig spinal cord (GPSC) emulsified in CFA. Rats preimmunized with peptide in CFA developed severe EAE. Rats preimmunized with hsp-CNP peptide in IFA were protected from EAE, with both a lower incidence and severity of disease. Injecting the murine monoclonal antibody recognizing the shared HSP65 and CNP epitope did not protect against EAE. Our data suggest that a Th2 pattern of immune response to a CNP peptide that itself is non-encephalitogenic protects against EAE. Immune responses to either hsp or myelin proteins cross-reactive with hsp may play an important role in the development of EAE.

Spinal fluid lymphocytes from a subgroup of multiple sclerosis patients respond to mycobacterial antigens.

Immune responses to heat shock or stress proteins are observed in several chronic autoimmune diseases. Such proteins are major antigens of many bacteria, especially mycobacteria. To determine whether immune responses to stress proteins occur in chronic inflammatory diseases of the central nervous system such as multiple sclerosis (MS) we measured proliferative responses of lymphocytes from spinal fluids and bloods of patients with MS and other neurological diseases to a sonicate of M. tuberculosis, an acetone extract of M. tuberculosis, a recombinant 65-kd heat shock protein of M. leprae, and tetanus toxoid as a control recall antigen. Significantly increased spinal fluid lymphocyte responses to mycobacterial sonicate, relative to responses from paired peripheral blood lymphocytes, were present in 14 of 20 specimens from patients with MS (p < 0.025) and 2 of 9 specimens from patients with other neurological diseases. Spinal fluid lymphocytes also responded to tetanus toxoid, but differences between blood and spinal fluid were not statistically significant. Lymphocytes from 1 patient with MS responded only to M. leprae. There were no proliferative responses to the M. tuberculosis acetone extract. When patients with MS were classified according to duration of disease (< 2- or > 2-yr duration) 9 of 10 patients with recent onset had cerebrospinal fluid cells that responded to M. tuberculosis compared with 5 of 10 with longer duration symptoms (p < 0.012). Our data suggest a selective recruitment and/or expansion of mycobacterial reactive cells to the central nervous system of a subpopulation of patients with MS.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of regulatory cells in spinal fluid and blood in patients with multiple sclerosis and other neurologic diseases.

Multiple sclerosis is a disease in which immune abnormalities are present both in the CNS and peripheral blood. Whether these changes are primary or secondary to the disease process is not known. We tested T-cell clones derived from activated lymphocytes in the blood and CSF of MS patients and controls for their capacity to regulate T-cell responses to alloantigens. A wide spectrum of regulatory functions were observed, ranging from marked enhancement to almost complete suppression. Clones from different patient populations and anatomic sites were equivalent in their regulatory functions with the net effect of clones in each compartment being suppression. However, certain clones from CSF and peripheral blood had the capacity to stimulate autologous T cells. Percentages of such clones in the peripheral blood of MS patients were significantly higher than in controls, while percentages in MS and other neurologic diseases (OND) CSF were equivalent. Our data suggest that (1) functional suppressor cells are not lost from the blood or CSF or MS and OND patients, (2) lymphocytes that have entered the CNS in patients with MS and other CNS diseases have equivalent regulatory functions, (3) MS may be an illness in which peripheral immunologic events are important in perpetuating the disease process, and (4) responses to autologous antigens may also play a role in this perpetuation.

Immunologic differences in murine glial cells and their association with susceptibility to experimental allergic encephalomyelitis.

We tested the hypothesis that glial cells from mice resistant or susceptible to the autoimmune disease experimental allergic encephalomyelitis (EAE) may differ in their abilities either to express Ia antigens and/or stimulate anti-class II (Ia)-specific T-cells. Ia antigens were induced on glial cells from EAE-susceptible (SJL/J) and -resistant (B10.S and DBA/2) strains of mice by culture with lymphokines from activated T-cells (2 degrees SN). Ia antigen expression was quantified with an enzyme-linked immunosorbent assay (ELISA) in which glia were exposed to monoclonal anti-Ia antibodies and alkaline phosphatase-labeled anti-mouse Ig antibodies. The ability of glial cells to stimulate anti-Ia T-cells was quantified by culturing irradiated glial cells with anti-Ia-specific T-cell lines and measuring the amounts of [3H]thymidine incorporated by these lines. Glial cells from all strains of mice could be induced to express Ia antigens and upon exposure to high concentrations of lymphokines, amounts of expressed Ia antigen were equivalent. However, at limiting lymphokine concentrations, glia from the EAE-resistant strain B10.S expressed greater amounts of Ia antigen than did glia from SJL/J mice (p less than 0.05), suggesting that B10.S glia were more sensitive to the Ia-inducing effects of T cell lymphokines. In contrast to the above results, glia from EAE-susceptible SJL mice consistently demonstrated an increased ability to induce T-cell proliferation in lines specific for Ias antigen, compared to glia from EAE-resistant mice, even those of the same Ia haplotype (i.e. B10.S). Spleen cells from resistant strains had equivalent and frequently greater ability to induce anti-Ia-specific T-cell proliferation than did SJL spleen cells. These data suggest (a) that there are differences in the sensitivity of glia from different strains of mice to the Ia antigen-inducing effects of T-cell lymphokines, (b) that expression of Ia antigen does not necessarily correlate with the ability to stimulate Ia-specific T-cells, (c) that there are organ-specific differences in the ability to stimulate Ia antigen-specific T-cells, and (d) that an additional variable involved in determining resistance or susceptibility to an organ-specific autoimmune disease may be the ability of the target organ to stimulate anti-Ia-specific T-cells.

Search for autonomously proliferating spinal fluid lymphocytes in patients with multiple sclerosis.

Recently published reports have suggested that multiple sclerosis (MS) may be associated with human retrovirus infection. Indeed, an autonomously proliferating T-cell clone was isolated from the CSF of an MS patient, an observation interpreted as indicating an infection with human T lymphotropic virus I (HTLV I). In view of these findings, we undertook a systematic search for autonomously proliferating cells in the spinal fluids of MS patients and those with other neurologic diseases (OND). In vivo activated blast cells were isolated from the CSF of six MS patients and six OND controls. A total of 442 clones were grown from these cells and assayed for their ability to proliferate independently, without the need for T cell-produced lymphokines. No autonomously proliferating clones were detected. Thus, while our data do not exclude the possibility that HTLV I transformed cells may exist in the CSF of MS patients, they do suggest that such cells are exceptional.

Disparate responses of lymphocyte clones to cells of monozygotic twins discordant for multiple sclerosis.

Spinal fluid and peripheral blood lymphocytes from patients with multiple sclerosis (MS) and other neurologic diseases (OND) were stimulated with a pool of allogeneic MS lymphocytes. Responding cells were cloned and assayed for their proliferative responses to peripheral blood lymphocytes from monozygotic twins discordant for MS. As expected, most (greater than 90%) responding clones proliferated equally well to cells from both members of a twin set. However, some clones were noted that responded to cells from one but not the other of the twin set. These differences could not be explained on the basis of a decreased stimulatory capacity of the twin cells. We cannot definitively explain our observations but they may suggest that environmental factors, perhaps exposure to a virus, could have altered the antigenic phenotypes of cells from identical twins discordant for MS. Further evaluation of the nature of these differences may lead to an understanding of the pathogenesis of the disease.

Spinal fluid lymphocytes responsive to autologous and allogeneic cells in multiple sclerosis and control individuals.

Spinal fluid lymphocytes from multiple sclerosis (MS) patients and controls were stimulated with either autologous non-T cells or with allogeneic non-T cells followed by stimulation with autologous non-T lymphocytes. Cells responding to these stimuli were cloned and their proliferative responses to autologous and allogeneic MS and normal non-T cells were measured. Large numbers of clones with specific patterns of reaction to both autologous and allogeneic cells were obtained from lymphocytes in MS cerebrospinal fluid (CSF), but only occasionally from cells in control CSF. Patterns of responses among clones from a particular CSF were similar and often identical, which suggested that cells in MS CSF were relatively restricted in their specificities. Surface antigen phenotyping of the clones showed them to be predominantly OKT4+, with 13% OKT8+ and 11% OKT4+8+. Peripheral T cells that were stimulated and cultured in parallel with CSF cells were different in that they usually did not give rise to as many clones nor were their patterns of response similar. Many CSF clones were heteroclitic, that is they responded to particular allogeneic cells but not autologous cells. Lymphocytes in MS CSF thus appear to represent a selected population of cells with a high frequency of responsiveness to autologous and allogeneic antigens. Such responses may be evidence for immune regulation within the central nervous system or could represent responses to altered-self antigens.

Autologous lymphocyte proliferation in multiple sclerosis and the effect of intravenous ACTH.

The proliferative response of peripheral blood T cells to autologous non-T cells, a reaction called the autologous mixed lymphocyte reaction (MLR), was significantly increased in 17 patients with active multiple sclerosis (MS) compared to age- and sex-matched individuals with other neurological diseases (OND). Following a 10-day course of intravenous adrenocorticotropic hormone (ACTH) therapy the values were reduced to control levels. No differences were noted between MS patients and controls in their response to alloantigens. The increased autologous MLR in patients with active MS appeared to result from an increased stimulatory capacity of non-T cells rather than from an intrinsically greater T cell proliferative potential. ACTH appeared to induce a change in the populations of circulating non-T cells such that these cells had a decreased stimulatory capacity in both autologous and allogeneic MLR. The decrease in stimulatory capacity in autologous MLR was, however, significantly greater than the decrease in allogeneic stimulatory capacity, suggesting a functional decrease of specific non-T cell-enriched subpopulations. No significant changes in the numbers of myeloperoxidase-positive (MP+) cells were noted in the blood of MS patients before and after ACTH therapy. Since the autologous MLR results in generation of cells that regulate immune responsiveness, the changes noted provide additional evidence for abnormal immune regulation in MS.