In vivo demyelination by antimyelin antibodies

B cells play a cooperative role via CD40L-CD40 interaction in T cell-mediated experimental autoimmune neuritis in Lewis rats

The expression of co-stimulatory molecules CD40 and CD40L was examined over the course of experimental autoimmune neuritis (EAN) induced in Lewis rats by immunization with bovine peripheral nerve myelin. In draining lymph nodes, highest level of CD40L expression was seen on day 7 post immunization (p.i.), i.e. before onset of clinical signs of EAN, while CD40 expression was increased on day 14 p.i., i.e. at peak of clinical disease. In contrast, both CD40 and CD40L expressing cells in sciatic nerves, a target organ of EAN, peaked on day 14 p.i., large numbers of both expressing cells were mainly detected on day 14-21 p.i. After co-culture with EAN rat B cells bearing CD40, P0 peptide 180-199-specific T cell line cells exhibited a rapid down-regulation of CD40L expression. Furthermore, EAN rats had enhanced P0 peptide 180-199-specific antibody responses on day 14 p.i., which might have contributed to their aggravated EAN and further demonstrated the role of antibodies in EAN. The results indicate that CD40L-CD40 interactions are involved in the initiation of the antigen-specific T cell responses associated with the generation and development of EAN, and may mediate autoantibody production in EAN. Evidently, B cells play a cooperative role via CD40L-CD40 interaction in T cell-mediated EAN of Lewis rats.

Resistance and susceptibility to experimental autoimmune neuritis in Sprague-Dawley and Lewis rats correlate with different levels of autoreactive T and B cell responses to myelin antigens

Experimental autoimmune neuritis (EAN) is a CD4+ T cell-mediated, inflammatory demyelinating disease of the peripheral nervous system (PNS) that serves as a model for Guillain-Barré syndrome (GBS) in humans. Various mouse and rat strains show different susceptibilities to EAN that can be induced by immunization with bovine PNS myelin (BPM) + Freund's complete adjuvant (FCA). We examined PNS-induced T and B cell responses and cytokine protein production as well as mRNA expression to study the mechanisms behind susceptibility to EAN in Lewis rats and resistance in Sprague-Dawley (SD) rats. Lewis rats with EAN have elevated PNS myelin-reactive interferon-gamma (IFN-gamma) production, TNF-alpha mRNA expression, and increased B cell responses to PNS myelin antigens, but low PNS myelin-reactive transforming growth factor-beta (TGF-beta) and interleukin (IL)-10 mRNA expression in lymph node mononuclear cells (MNC). In contrast, resistance to EAN in SD rats is associated with reduced BPM and P2 peptide-reactive IFN-gamma production, TNF-alpha mRNA expression, and suppressed B cell responses to PNS myelin antigens as well as up-regulation of TGF-beta and IL-10 mRNA expression. Resistance to EAN is also associated with low-grade inflammation or absence of histological evidence of EAN. These results suggest that differential autoreactive T and B cells responses to PNS myelin antigens are strain specific, and the susceptibility to EAN is related to quantitative rather than qualitative differences in distribution between proinflammatory and anti-inflammatory cytokines.

The B cell repertoire in experimental allergic neuritis involves multiple myelin proteins and GM1

Experimental allergic neuritis (EAN) is a T cell mediated disease associated with inflammation and demyelination of peripheral nerves. EAN is an experimental model of Guillain-Barré syndrome. The peripheral nerve myelin components P2 and P0 represent major neuritogens, but the diversity and quantity of B cell responses in EAN are unknown. Lewis rats were immunized with bovine peripheral nerve myelin (BPM), and levels of B cells secreting IgM and IgG antibodies to BPM, P2 and P0, the glycolipid GM1 and five peptides of myelin-associated glycoprotein (MAG) were determined. Already on day 7 post-immunization (p.i.), i.e. before the onset of clinical EAN, lymph nodes contained elevated levels of cells secreting IgM antibodies of all specificities examined. Maximum numbers of IgG antibodies secreting cells were generally reached at the height of clinical disease. The numbers of cells secreting IgG antibodies to BPM, P2, P0, GM1 and MAG peptides were also elevated before disease onset, but they were mostly higher than those of IgM antibodies and they reached their maximum only after recovery. The results imply that EAN is associated with strong B cell responses to all myelin antigens under study without restriction to any immunodominant myelin component or MAG peptides.

Autoantibody responses in the cerebrospinal fluid of guinea pigs with chronic relapsing experimental allergic encephalomyelitis

We report the use of the ELISA technique to measure IgG specific for whole cord, myelin, myelin basic protein and Mycobacterium tuberculosis in the cerebrospinal fluid (CSF) of Strain 13 guinea pigs in different stages of chronic relapsing experimental allergic encephalomyelitis (CR-EAE). Specific antibody levels to all 4 antigen preparations were related to the severity of clinical signs, with the highest levels of IgG in the CSF of guinea pigs in relapse or in stable chronic disease. Total IgG levels in the CSF, though elevated throughout the course of CR-EAE, did not show any association with the category of disease. Control animals inoculated with complete Freund's adjuvant (CFA) alone showed CSF IgG levels specific for M. tuberculosis that were not significantly different from those in animals with chronic EAE, indicating that CFA may itself induce a late-acting increase in blood-brain barrier permeability.

Experimental allergic encephalomyelitis: the balance between encephalitogenic T lymphocytes and demyelinating antibodies determines size and structure of demyelinated lesions

The effect of a circulating monoclonal antibody recognizing an antigen located on the surface of myelin sheaths (myelin/oligodendroglia glycoprotein, MOG) on clinical and histopathological expression of experimental allergic encephalomyelitis (EAE) was tested in a model of EAE passively transferred by monospecific T lymphocytes. Intravenous injection of anti-MOG antibody at the onset of the disease massively augmented clinical impairment as well as primary demyelination. The structure of the CNS lesions depended on the balance between encephalitogenic T cells and anti-MOG antibody: when EAE was induced with high numbers of T cells, circulating anti-MOG antibody resulted in ubiquitous perivenous demyelination in the spinal cord and medulla oblongata. On the contrary, focal confluent demyelinated lesions were observed in animals injected with low numbers of T cells (even as few as 10(4] and anti-MOG antibody. Our studies, thus, indicate that the formation of inflammatory demyelinating lesions may be due to a synergistic action of cellular and humoral immune mechanisms.

Myelin changes in the rats CNS following intraventricular injection of serum

Normal human or rat serum administered by intraventricular injection induced demonstrable changes in the rat CNS myelin as seen from an increased recovery of dissociated myelin (DM), i.e. a myelin-related low density membrane fragments, from the tissue homogenates. The yield of DM reached a maximum on the third postinjection day and returned to the control level by day 5. In spite of the increased recovery of DM, no physico-chemical alternations in myelin isolates and no histological abnormalities in the tissue could be detected. The production of DM seems to be a sensitive index of serum-induced alteration of the myelin sheath.

In vivo demyelinating activity of sera from animals with chronic experimental allergic encephalomyelitis. Antibody nature of the demyelinating factor and the role of complement

Sera from guinea pigs and rats with chronic experimental allergic encephalomyelitis were injected into the cerebrospinal fluid (CSF) of normal recipient rats. Guinea pig sera induced demyelination in the central and (or) peripheral nervous system, whereas injection of rat sera resulted in demyelination in the peripheral nervous system only. Control sera did not induce demyelination. Demyelinating activity in guinea pig sera was confined to the IgG-fraction; in rat sera the IgG- as well as the IgM-fraction were able to induce demyelination. The demyelinating activity was abolished when the sera were absorbed with with sensitising antigen (guinea pig spinal cord tissue) or when immunoglobulins were removed from the sera. When chronic EAE sera from rats were injected into the CSF of rats, complement was not required for the induction of demyeLination. The presence of complement, however, augmented the demyelinating activity. Decomplemented chronic EAE sera from guinea pigs failed to induce demyelination after injection into the CSF of rats. Injection of control and non-demyelinating or demyelinating EAE sera into the subarachnoid space of normal recipient rats induced a weak inflammatory response with increased numbers of large mononuclear cells in the meninges. It is discussed that in vivo a complex interaction of antibodies, complement and effector cells is responsible for induction of demyelination.

Demonstration of serum IgG antibodies against myelin during the course of relapsing experimental allergic encephalomyelitis in guinea pigs

Chronic relapsing allergic encephalomyelitis (r-EAE) was induced in a local strain of guinea pigs. By the use of isoelectric focusing (IF) followed by antigen immunofixation and autoradiography, antibodies directed against central nervous system (CNS) myelin were detected in 21 of 23 sera sampled during the course of r-EAE. Previous absorption of the sera with CNS myelin reduced or abolished antibody activity on autoradiograms. One r-EAE guinea pig developed definite oligoclonal IgG bands in serum while in 7 r-EAE animals faint oligoclonal IgG bands were present. The mobility of oligoclonal IgG bands differed from the mobility of antimyelin antibody bands on autoradiograms. The significance of these findings has not been definitely elucidated but the antimyelin antibodies may possibly be involved in the pathogenesis of the disease while oligoclonal IgG bands may represent an epiphenomenon not pathogenetically related to r-EAE.

Shared antigenic determinants between brain and thymus-derived lymphocytes in dogs

Canine anti-canine myelin, canine distemper convalescent, and control sera were tested for the presence of antilymphocyte antibodies in a complement-dependent microcytotoxicity assay. Sera were cytotoxic for CT 45-S cells, a canine origin thymic lymphoma, canine thymocytes, and phytomitogen-transformed canine peripheral blood lymphocytes. The cytotoxic effect was removed by absorption with canine white matter but not by absorption with galactocerebroside. The data suggests that the specificity of antimyelin and antilymphocyte antibodies is directed toward a common antigen (canine Thy-1). It is likely that, in canine distemper, these antibodies are produced following the lymphotropic phase of viral infection. The possibility that similar autoimmune phenomena observed in multiple sclerosis patients occur via an unrecognized infectious event in lymphoid tissues is raised.

Mild encephalitogenic activity of basic protein--acidic lipid complex from myelin and detection of immune complexes in experimental allergic encephalomyelitis

Further biochemical and pathological investigation of basic protein--acidic lipid complex from canine cerebral myelin show the presence of sulfatide, phosphatidylserine, ganglioside and basic protein in the molar ratio of approximately 6 : 3 : 1 : 1 and that it is associated with mild encephalitogenic activity in guinea pigs in comparison to intact myelin and basic protein. Circulating immune complexes were detected in the sera of guinea pigs with clinical signs of experimental allergic encephalomyelitis and immunofluorescent staining showed the deposition of immune complexes of immunoglobulin and complement in vessels of white matter and meninges and in the choroid plexus.

In vivo effect of sera from animals with chronic relapsing experimental allergic encephalomyelitis on central and peripheral myelin

Sera from guinea pigs with acute or chronic relapsing experimental allergic encephalomyelitis (EAE) were injected into lumbosacral subarachnoid space of normal recipient rats. Seventeen of 37 sera induced demyelination in the CNS, and 27 of 37 sera caused demyelinated peripheral nerve fibers in the roots. The highest incidence of demyelinating activity of EAE sera was noted in those from donor animals sampled during the early chronic stage of the disease [40--100 days post sensitization (dps)]. Only few sera from animals sampled during the acute and subacute stage (10--40 dps) were able to induce demyelination. Sera from animals sampled between 100 and 200 dps showed a lower incidence of demyelinating activity as compared to those from the early chronic phase of the disease. There was no clear-cut correlation between the serum-demyelinating activity and the severity of the demyelinating disease in the donor animals. The patterns of demyelination in the central as well as peripheral nervous system of recipient animals were characterized by vesicular disruption of myelin or myelin stripping. Myelin degradation was performed mainly be macrophages. In the CNS some astrocytes also contained debris. Astrocytes increased in size, and mitosis of astrocytes was observed. Oligodendrocytes appeared to be unaffected. No demyelination was found when the sera from animals sensitized with CFA alone or with guinea pig liver tissue were injected into the subarachnoid space of normal recipient rats. Two possible mechanisms of demyelination are discussed: Antibody-mediated complement-dependent and antibody-dependent cell-mediated demyelination.