Effect of anti-interferon-γ monoclonal antibody treatment on the development of experimental allergic encephalomyelitis in resistant mouse strains

Immunization with myelin basic protein (MBP) in complete Freund's adjuvant failed to induce experimental allergic encephalomyelitis (EAE) in six resistant mouse strains studied: A/J, BALB/c C3H/HeJ, AKR, NZW and DBA/2. However, treatment of challenged mice with anti-interferon-γ (IFN-γ) monoclonal antibody (mAb) induced severe EAE in mice of all strains except AKR. Furthermore, anti-IFN-γ mAb treatment led to increased disease incidence and severity in BALB/c mice challenged with the MBP peptide_87–103, known to be encephalitogenic for the susceptible SJL strain. In three strains tested, anti-IFN-γ mAb enhanced passively induced EAE in the A/J and C3H/HeJ but not in the BAlB/c mice. All mice with clinically overt EAE had widespread histological lesions characterized by mononuclear cell infiltrates and focal demyelination. The results indicate that resistant strains are genetically capable of developing EAE, and that IFN-γ can contribute to disease resistance.     

Susceptibility of experimental allergic encephalomyelitis in two strains of rats and their hybrids

Summary Lewis and PVG strains of rats and their F₁-hybrids were challenged with guinea-pig or bovine encephalitogenic protein (EP) in Freund's complete adjuvant (FCA) to produce experimental allergic encephalomyelitis (EAE). The Lewis and F₁-rats were also challenged with guinea-pig EP in FCA with a fivefold lower concentration of Mycobacterium butyricum. Data are presented concerning clinical signs und histological changes of EAE showing an intermediate position of susceptibility to EAE for the F₁-hybrids compared to the parental strains. The findings are discussed in relation to the mode of inheritance of susceptibility of EAE. Among rats immunized with bovine encephalitogenic protein in FCA a weak activity was registered; this was difficult to evaluate, as it could be an effect of FCA only.Abbreviations EAE Experimental allergic encephalomyelitis - EP Encephalitogenic protein - FCA Freund's complete adjuvant     

Inhibition of chronic relapsing experimental allergic encephalomyelitis in the Biozzi AB/H mouse

Chronic relapsing experimental allergic encephalomyelitis (CREAE) can be reproducibly induced in Biozzi AB/H mice following injection of spinal cord homogenate (SCH) emulsified in complete Freund's adjuvant (CFA). Active clinical disease is associated with mononuclear cell infiltration of the central nervous system (CNS), mainly the spinal cord. Whole brain homogenate (BH), however, failed to induce clinical or histological disease. In contrast, substituting sciatic nerve homogenate in the inoculum induced experimental allergic neuritis (EAN). Clinical disease was manifest earlier (13.1 +/- 0.3 days) than CREAE (16.2 +/- 1.4) and was accompanied by mononuclear infiltration of the peripheral nervous system (PNS). In comparison to CREAE induction, pretreating mice with SCH or BH in incomplete Freund's adjuvant (IFA) suppressed the development of SCH-induced disease. The BH was more tolerogenic than the SCH and this hyporesponsiveness was CNS antigen-specific as PNS tissue failed to inhibit the course of CREAE. Tolerance induced by pretreatment with SCH or BH in IFA was reversed by a single injection of 200 mg/kg cyclophosphamide, 2 days prior to CREAE induction. This suggests that IFA-induced hyporesponsiveness is actively regulated, possibly via the action of suppressor cells. In addition, treatment with neuroantigens in IFA appears to be mainly afferent acting as it serves to prevent initial disease induction. This treatment after immunization for CREAE, however, fails to prevent disease progression. Furthermore, treatment with CNS antigens emulsified in IFA during the post-acute remission stage appeared to synchronize and induce (32 +/- 1 days) the onset of clinical relapse, compared with untreated controls (41 +/- 5 days). This indicates that such IFA treatment has minimal value in controlling an ongoing immune disease of the CNS.     

Neuroprotection of axons with phenytoin in experimental allergic encephalomyelitis

Voltage-gated sodium channels contribute to the development of axonal degeneration in white matter, and sodium channel blocking drugs are known to have a protective effect on acutely injured white matter axons. To determine whether phenytoin has a protective effect on axons in a neuroinflammatory model, we studied the effect of phenytoin on axonal degeneration in the optic nerve in MOG-induced experimental allergic encephalomyelitis (EAE). We report that, whereas approximately 50% of optic nerve axons are lost at 27-28 days in untreated EAE, only approximately 12% of the axons are lost if mice with MOG-induced EAE are treated with phenytoin. These results demonstrate that it is possible to achieve substantial protection of white matter axons in EAE, a model neuroinflammatory/demyelination disease, with a sodium channel blocking agent.     

Anti-endothelial cell antibody and immune complexes in the sera of animals with acute experimental allergic encephalomyelitis and chronic relapsing experimental allergic encephalomyelitis

Blood-brain barrier (BBB) injury occurs in both acute and chronic relapsing experimental allergic encephalomyelitis (EAE). Sera from animals in which these forms of EAE had been induced were examined for anti-endothelial cell antibodies and immune complexes by enzyme-linked immunosorbent assay (ELISA) using either cultured endothelial cells or Raji cells. IgG binding to endothelial cells was significantly increased in the sera of animals with acute EAE and chronic relapsing EAE, compared to controls. Increased levels of circulating immune complexes were also detected in the sera of some animals with chronic relapsing EAE, especially those in an exacerbation. It is suggested that the anti-endothelial cell antibody and immune complexes detected may play pathogenetic roles in the destruction of the BBB in EAE.     

Adoptive transfer of experimental allergic encephalomyelitis

We have previously shown that adoptive transfer of experimental allergic encephalomyelitis can be greatly enhanced by culturing sensitized lymph node cells (LNC) with specific antigen, myelin basic protein (BP). In the present study, successful transfer was accomplished with 5×10⁶ Lewis rat LNC after 48 h culture with BP. Disease transfer was inhibited by the addition to culture of dibutyryl adenosine 3’,5’-cyclic monophosphate (Bt₂ cAMP) or the phosphodiesterase inhibitor, isobutyl methylxanthine (MIX), but not by Bt₂cGMP. BP-induced lymphoproliferation was also inhibited, but with a slightly different dose-response relationship. An early step in the lymphocyte activation process appears to be most sensitive to the inhibitory effects of Bt₂cAMP.     

Immunomodulation of relapsing experimental allergic encephalomyelitis

Mice immunized to produce relapsing experimental allergic encephalomyelitis (R-EAE) were treated with immunomodulating agents known to affect acute monophasic experimental allergic encephalomyelitis. Pretreatment with either mouse spinal cord or myelin basic protein in incomplete Freund's adjuvant decreased the incidence of R-EAE from 77% to 28 and 31%, respectively. Single doses of cyclophosphamide (CY) at the time of immunization did not affect development of R-EAE. CY given repetitively in low doses decreased the incidence of R-EAE to 10%. Therefore, R-EAE can be altered by immunomodulation, but the patterns differ from those seen in acute EAE.     

Visual evoked potentials in experimental allergic encephalomyelitis

We have compared the clinical signs, brain pathology and visually evoked responses (VEP) of guinea pigs with experimental allergic encephalomyelitis (EAE). Animals immunized with myelin basic protein had a milder disease, both from the clinical and histological points of views, compared to those immunized with crude white matter extract. However, VEP findings were quite similar in both groups. The VEP of the majority of animals from both groups showed changes before or at the same time that neurological signs appeared. Electrophysiological responses were usually characterized by abnormal wave shapes and prolonged latencies. Recovery of the VEP usually preceded the recovery from clinical signs. In contrast, the severity and incidence of brain tissue pathology was not correlated to either clinical signs or VEP changes. Possible explanations of the electrophysiological, clinical and histopathological changes and their time-course are discussed.     

Ascending impairment of nociception in rats with experimental allergic encephalomyelitis

An ascending impairment of tail nociception is a previously undescribed clinical sign of acute experimental allergic encephalomyelitis (EAE) in the rat. It occurs in EAE induced by inoculation with purified central nervous system (CNS) myelin basic protein (MBP) as well as with whole spinal cord. It is invariably present and consists of an absence of the vocalization response to noxious mechanical stimulation of the tail. This impairment of nociception evolves over 1-3 days, simultaneously with the development of tail weakness, and resolves more rapidly than the tail weakness. Light-microscopic, electron-microscopic and electrophysiological studies indicate that it is due to demyelination-induced conduction block in the small diameter myelinated afferent (A delta) fibres in the sacral and coccygeal dorsal root ganglia, dorsal roots and dorsal root entry zones. Unmyelinated fibres appear to be largely spared.     

Mast cell activity in experimental allergic encephalomyelitis

The number and functional reactivity of peritoneal mast cells (MCs) were evaluated in rats with experimental allergic encephalomyelitis (EAE). Cells were counted following staining with toluidine blue and activation was measured by B-hexosaminidase (B-hex) release. The number of detectable MCs and their capacity to release B-hex decreased significantly by 40 and 65%, respectively, as compared with normal controls just prior to the onset of clinical signs. These values returned to normal on clinical recovery. Preliminary data on MC counts performed on histological sections of rat brains with EAE suggested a similar pattern of response, i.e., an early decrease prior to disease onset with subsequent normalization on recovery. In an attempt to modify the course of EAE, rats were treated with the MC stabilizing agent nedocromil or with the MC activating agent, compound 48/80. Nedocromil induced a slight delay in the onset of EAE, but only when administered at the time of EAE induction. Compound 48/80 did not seem to affect the clinical course of the disease. Our results suggest that MCs are involved in the pathogenesis of EAE and may contribute to the induction of the disease rather than to the effector phase and its clinical expression.