Ute Traugott

Multiple sclerosis: Distribution of T cells, T cell subsets and Ia-positive macrophages in lesions of different ages

Using monoclonal antibodies in combination with the PAP technique, total (T11+) T cells, helper-inducer (T4+) T cells, suppressor-cytotoxic (T8+) T cells and Ia+ cells (macrophages and B cells) were localized in frozen sections of multiple sclerosis (MS) lesions with varied disease activity. In acute MS, T11+, T4+, T8+ cells and Ia+ macrophages were found in large numbers throughout the lesion but were virtually absent from normal white matter. In active chronic MS lesions, the numbers of T11+, T4+ and T8+ cells increased from the center towards the edge of the lesion. T11+ and T4+ cells penetrated deeply into the normal-appearing white matter adjacent to the lesion, while T8+ cells were more confined to the lesion edge. Ia+ macrophages displayed a reverse distribution pattern to that of T cells. They showed the highest density in the lesion center and their numbers decreased slightly towards the lesion edge. Small numbers of T11+, T4+, T8+ and Ia+ cells were always present in normal white matter. In silent chronic MS lesions, the numbers of both T cells and Ia+ cells were significantly lower than in active chronic MS. While T11+ and T4+ cells were found throughout the central nervous system (CNS), T8+ cells were virtually absent from the lesion center. Ia+ macrophages were also present in small numbers throughout the CNS and, sometimes, showed some accumulation at the lesion edge. Thus, T cells and T cell subsets have been demonstrated to be involved in lesion pathogenesis in MS in that lesion progression was associated with T4+ cells while ongoing demyelination depended upon the presence of Ia+ macrophages.

On the presence of Ia-positive endothelial cells and astrocytes in multiple sclerosis lesions and its relevance to antigen presentation.

Using a monoclonal antibody in combination with the 4-step modified peroxidase-antiperoxidase (PAP) technique, Ia expression was demonstrated on endothelial cells and astrocytes in MS lesions of different ages. On endothelial cells, Ia antigen was found most frequently in grey and white matter parenchyma of acute MS brain and showed lower, comparable numbers in active and silent chronic MS brain tissue. Ia+ astrocytes were most numerous in acute MS lesions. In active chronic MS, Ia+ astrocytes predominated at the lesion edge, where they frequently displayed an atypical, rounded configuration. Positive astrocytes showed somewhat lower numbers within the lesion center and in normal white matter close to the lesion edge. Their frequency was significantly lower in normal white matter remote from the lesion. In silent chronic MS, Ia+ astrocyte processes were detectable only within the lesion center. Grey matter astrocytes displayed no staining with anti-Ia antibody. In normal brain tissue, no Ia antigen could be detected. The presence of Ia molecules on some endothelial cells and astrocytes in MS brain tissue suggests a role in antigen presentation perhaps relevant to the initiation and perpetuation, respectively, of the inflammatory process.

Multiple sclerosis: relevance of Class I and Class II MHC-expressing cells to lesion development

Expression of Class I (HLA-ABC) and Class II (HLA-Dr; Ia) major histocompatibility (MHC) antigens on endothelial cells and astrocytes was investigated in multiple sclerosis (MS) lesions of variable disease activity and in normal central nervous system (CNS) using immunocytochemical techniques. Findings were correlated to lesion pathology and to the presence and distribution of T cells, T cell subsets, and interleukin-2 (IL-2) receptor-bearing cells. HLA-ABC was present on virtually all endothelial cells in normal and pathologic tissue samples. Ia was absent from controls and was detectable on about 10% of CNS endothelial cells in MS. In normal CNS, astrocytes were Ia-negative and rarely expressed HLA-ABC. In MS, Class I and II MHC-positive astrocytes were found, and both displayed a high frequency in active lesions. Class I-reactive glia were primarily associated with T cell infiltrates and were less common in older lesions in which macrophages predominated. In contrast, Class II-positive astrocytes were found in all active MS lesions independent of the composition of inflammatory cells. Expression of HLA-ABC and Ia molecules on astrocytes in MS lesions could indicate their involvement in local presentation of antigen to cytotoxic (T8+) and helper/inducer (T4+) T cells, respectively. The observed distinct distribution patterns of HLA-ABC and Ia-positive astrocytes might suggest that cytotoxic T8+ cells are operative early during lesion development in MS. This could be followed by a more extensive Class II MHC-restricted helper T cell-mediated immune response which leads to selective destruction of myelin via activated macrophages.

Interferon-γ and Ia antigen are present on astrocytes in active chronic multiple sclerosis lesions

Using immunocytochemical techniques, presence of interferon (IFN)-γ, IFN-α and Class II major histocompatibility (MHC) antigen (HLA-DR, Ia) was evaluated in active central nervous system (CNS) lesions of 11 patients with chronic multiple sclerosis (MS) and the findings were correlated with a detailed analysis of inflammatory cells. Both IFN-γ and Ia antigen were detectable on astrocytes at the edge of active chronic MS lesions and in the adjacent normal-appearing white matter, where CD4+ (helper/inducer) T cells and interleukin-2 receptor (IL-2R)-positive cells were also found. IFN-α was predominantly seen on Ia-positive macrophages and not on astrocytes. Astroglia in the inactive lesion center and in normal CNS parenchyma were unreactive for both types of IFN and Ia antigen. These findings suggested that similar to the situation in vitro, IFN-γ can also induce Ia-expression on astrocytes in vivo. Via local antigen presentation, IFN-γ might thus play an important role in the development of MS lesions, while IFN-γ might be involved in local immunosuppression.

Acute experimental allergic encephalomyelitis in the mouse: immunopathology of the developing lesion.

To investigate the sequence of immunopathologic events during lesion formation in acute experimental allergic encephalomyelitis (EAE), SJL/J mice were inoculated with isogeneic spinal cord in complete Freunds adjuvant (CFA) and with Bordetella pertussis on Days 1 and 3 postinoculation (PI). Mice were sampled at different time points PI and T cells, T-cell subsets. Ia+ cells, Ig+ cells, albumin, and Ig deposits were localized in frozen sections by the avidin-biotin complex (ABC) method and direct fluorescence. Furthermore, samples were stained for Ia antigen, myelin basic protein (MBP), and galactocerebroside (GC) localization on endothelial cells by the ABC technique. Clinical and pathologic observations were correlated with the immunopathologic results. It was found that early in the disease process myelin and Ia-antigens were demonstrable on endothelial cells within the central nervous system (CNS). Simultaneously, damage to the blood-brain barrier was apparent, as indicated by albumin deposits, and small numbers of infiltrating T cells, T-cell subsets, and Ia+ cells were found. With time PI, the density of infiltrating total T cells (Thy-1.2+), helper/inducer (Lyt-1+), and suppressor/cytotoxic (Lyt-2+) T cells increased; Lyt-1+ and Lyt-2+ cells were detectable in meningeal as well as parenchymal infiltrates, while later on, Lyt-1+ cells showed some predilection for the CNS parenchyma and Lyt-2+ cells for meninges. Ia+ cells (B cells, macrophages, activated T cells) were present in small numbers only. Ig+ cells (B cells and macrophages) appeared shortly before onset of signs and persisted in moderate numbers. These results reconfirm the importance of early T-cell involvement for the development of EAE; they might also indicate a secondary role for Ig+ cells and are consistent with the concept that presentation of myelin antigens to T cells might occur locally on Ia-bearing endothelial cells within the CNS.

Immunopathology of the lesion in chronic relapsing experimental autoimmune encephalomyelitis in the mouse

To analyze immunopathologic events within the central nervous system (CNS) during various stages of actively induced chronic relapsing EAE in SJL/J mice, animals were sampled at various timepoints post inoculation (PI) and T cells, T-cell subsets, Ia+ cells and Ig+ cells, albumin, and Ig deposits were localized in frozen sections by immunocytochemical techniques. Furthermore, sections were stained for the demonstration of Ia antigen, myelin basic protein (MBP), and galactocerebroside (GC) on endothelial cells and astrocytes. During the acute phase of the disease, large numbers of all types of inflammatory cells studied (Lyt-1.2+, L3T4+, Lyt-2+, Ia+, Ig+) were randomly distributed throughout lesions, a finding similar to that described previously for acute EAE. A more distinct distribution pattern of infiltrating T cells was found during active chronic disease in that L3T4+ cells predominated within the CNS parenchyma, while Lyt-2+ cells were more numerous in meningeal and perivascular areas. During all chronic stages, a low-grade diffuse infiltration of the neuraxis by hematogenous cells was present. Ia and myelin antigens were detectable on some endothelial cells and astrocytes. Damage to the blood-brain barrier, as indicated by albumin and Ig deposits, was more extensive during the acute than during chronic stages of the disease. Taken in concert, the results further support the possibility of local antigen presentation on endothelial and astroglial cells and an essential involvement of helper (L3T4+) T cells in CNS lesion formation. These findings correlate well with events reported previously in acute and chronic multiple sclerosis lesions.

Chronic relapsing experimental allergic encephalomyelitis: Identification and dynamics of T and B cells within the central nervous system

Abstract Using a monoclonal antibody against guinea pig T cells and anti-guinea pig immunoglobulins, T- and B-cell dynamics were studied by immunofluorescence in situ in the central nervous system (CNS) of animals with untreated and treated chronic relapsing experimental allergic encephalomyelitis (EAE). Treated animals were given a series of injections of either myelin basic protein (MBP) in incomplete Freunds adjuvant (IFA) or MBP and galactocerebroside in IFA. Within the CNS, T and B cells showed distinct distribution patterns in untreated chronic relapsing EAE, similar to that recently described in acute EAE. T cells were predominantly localized within the CNS parenchyma and B cells were mainly found in perivascular areas. B-cell infiltrates were more extensive than in acute EAE and, although most were centered around blood vessels, some were also detectable in the parenchyma. IgG, C 3 , and albumin deposits were common. These observations suggest an age-dependent difference in the immune response. In treated chronic EAE, the disease process was apparently arrested and T- and B-cell infiltrates in the white matter were negligible. Therefore, it appears that the present treatment protocol prevents lymphocytes from entering the CNS parenchyma.

Glial bridges and Schwann cell migration during chronic demyelination in the C.N.S.

SummaryThe formation of fibrotic bridges from subpial astrocytes into the subarachnoid space of the spinal cord and the migration of Schwann cells to the central nervous system (C.N.S.) is appraised in chronically demyelinated C.N.S. lesions. Spinal cord tissue was studied from inbred, Strain 13 guinea pigs with chronic experimental allergic encephalomyelitis (EAE). It has been found that uncommitted Schwann cells are present around remyelinated fibres in nerve root entry zones, between meningeal cells at a distance from the roots and along blood vessels within the spinal cord parenchyma. It is speculated that these cells migrate via the above route to the C.N.S. In the present model, this invasion might be aided by glial fibrosis, a process which leads to surface irregularities in the spinal cord, an extensive extracellular space and possible breaches in the glia limitans through which Schwann cells might penetrate.

The pathogenesis and therapy of multiple sclerosis is based upon the requirement of a combination of myelin antigens for autoimmune demyelination

It is postulated that the pathogenesis of demyelination in multiple sclerosis (MS) might lie in the cooperative effect of a T cell response against one myelin antigen (e.g. myelin basic protein--MBP) and a B cell response against a second myelin component which may act as a hapten or a carrier for the primary antigen. The hypothesis is based upon recent experiments in guinea pigs in which the encephalitogenicity of MBP was enhanced by the myelin glycolipid, galactocerebroside. This pathogenetic mechanism might be analogous to antibody-dependent, cell-mediated demyelination. Based upon this assumption, therapeutic trials in MS should take into consideration the possibility that instead of MBP alone, MBP might be more effective in combination with a lipid hapten.

Characterization and distribution of lymphocyte subpopulations in multiple sclerosis plaques versus autoimmune demyelinating lesions

For many years now, autoimmune phenomena have been implicated in the pathogenesis of multiple sclerosis (MS) and more recently this has been supported by reports on the sensitization of the cellular and humoral immune system against myelin components [25, 29, 32, 34, 43, 65] and the observation that decreases in circulating suppressor/cytotoxic (T8 +) T cells frequently occur during clinical exacerbations [2, 24, 63]. Surprisingly, during relapses helper/inducer (T4 +) T cells and not T8 + cells have been found to be activated in the cerebrospinal fluid [CSF25, 29, 32, 34, 37], an observation which might imply a more significant role for T4 + than T8 + cells in lesion pathogenesis. Despite increasing amounts of data on immunologic changes in the circulation in MS, until recent months, knowledge on immunopathologic changes within the target organ of this disease, the central nervous system (CNS), has been limited and was predominantly confined to descriptive analysis of MS lesions by routine pathology [1, 19, 49-53]. By these criteria, the chronic MS lesion is seen to consist of a sharply-demarcated area of demyelination with variable degrees of hypercellularity at the lesion edge and myelin degradation products serving as indicators of lesion activity. The inflammatory components in active MS lesions consist mainly of lymphocytes, macrophages, and plasma cells. Immunocytochemical studies have demonstrated deposits of IgG at the lesion edge and have confirmed the presence of plasma cells and immunoglobulin (Ig)-containing macrophages [13, 51, 52, 73]. The latter sometimes display a cap-like aggregation of IgG and have been claimed to be actively involved in myelin breakdown l-51, 52]. With the availability of monoclonal antibodies to subpopulations of hematogenous cells [28, 36, 62], more detailed analysis of inflammatory infiltrates in regard to their immunologic function has