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Two distinct CD28-specific mAb were used in treatment of active or adoptive transfer (AT)-experimental autoimmune neuritis (EAN): "superagonistic" JJ316 activates T cells without T cell receptor (TCR) occupancy, and conventional JJ319 activates T cells only in the presence of TCR-stimulation. Treatment with JJ316 during induction phase of active and adoptive-transfer experimental autoimmune encephalomyelitis (AT-EAN) dramatically reduced disease severity and improved nerve function as revealed by electrophysiology. JJ316 given 1 week before immunization had a preventive effect. By immunohistology, JJ316 markedly reduced TC infiltration of the sciatic nerve in active and AT-EAN. JJ319 was less effective. Ex vivo, JJ316 therapy reduced P2-specific proliferation and interferon-gamma (IFN-gamma) production of lymph node cells. We demonstrate preventive and therapeutic effects of a "superagonistic" mAb-mediated, TCR-independent CD28 stimulation in EAN, possibly with implications for therapy of autoimmune-inflammatory disorders.

Treatment of experimental autoimmune disorders of the nervous system with high doses of glucocorticosteroids (GC) or with administration of the specific antigen is effective and associated with marked T cell apoptosis in situ. Here we investigated in adoptive transfer-experimental autoimmune neuritis (AT-EAN) of the Lewis rat whether induction of T cell apoptosis resulting from T cell activation by antigen therapy can be further augmented by glucocorticosteroids (GC). AT-EAN was induced by intravenous injection of P2-specific T cell blasts. At the maximum of disease two pulses of the antigen recombinant human P2 (rhP2) were given within 12 h. Methylprednisolone was administered simultaneously or 2 h after the antigen and animals were killed 6 h after the second antigen injection. Using an in situ tailing technique followed by immunocytochemical analysis, the presence of DNA fragmentation in T lymphocytes was confirmed. The bromodeoxyuridine (BrdU) technique was employed to detect in situ proliferating cells. T cell apoptosis in sciatic nerve was enhanced after monotherapy with either antigen or GC compared to the control group receiving an irrelevant myelin protein, recombinant human P0. In combination therapy, a synergistic effect on T cell apoptosis in sciatic nerve was obtained when methylprednisolone was injected sequentially, 2 h after rhP2 protein. BrdU incorporation in the sciatic nerve as well as in the spleen, a major lymphoid organ, was significantly enhanced in animals treated with antigen followed by GC 2 h later as compared to rats receiving rhP2 only, speaking for T cell proliferation in situ associated with T cells undergoing apoptosis. Our findings underscore that different proapoptotic stimuli may act synergistically, depending on the timing of the second treatment. In this scenario even local T cell proliferation in the inflamed nervous system occurs. These results support the paradigm of antigen presentation in the nervous system.

High-dose Ag administration induces apoptotic death of autoreactive T cells and is an effective therapy of experimental autoimmune diseases of the nervous system. To explore the role of cytokines in Ag-specific immunotherapy, we analyzed mRNA induction and protein expression for the proinflammatory cytokines TNF-alpha and IFN-gamma, the anti-inflammatory cytokine IL-10, and the cytokine-inducible NO synthase (iNOS) during high-dose Ag therapy of adoptive transfer experimental autoimmune encephalomyelitis (AT-EAE) in the Lewis rat. Using semiquantitative and competitive RT-PCR, we found 5- to 6-fold induction of TNF-alpha mRNA and 3-fold induction of IFN-gamma mRNA in the spinal cord that occurred within 1 h after i.v. injection of Ag and was accompanied by a 2-fold increase of iNOS mRNA. Both IFN-gamma and iNOS mRNA remained elevated for at least 6 h, whereas TNF-alpha mRNA was already down-regulated 6 h after Ag injection. A comparable time course was found for circulating serum levels of TNF-alpha and IFN-gamma. IL-10 mRNA levels did not change significantly following Ag injection. Neutralization of TNF-alpha by anti-TNF-alpha antiserum in vivo led to a significant decrease in the rate of T cell and oligodendrocyte apoptosis induced by high-dose Ag administration, but did not change the beneficial clinical effect of Ag therapy. Our data suggest profound activation of proinflammatory but not of anti-inflammatory cytokine gene expression by high-dose Ag injection. Functionally, TNF-alpha contributes to increased apoptosis of both autoaggressive T cells and oligodendrocytes in the target organ and may thereby play a dual role in this model of Ag-specific therapy of CNS autoimmune diseases.

The adhesive cell surface molecule P(0) is the most abundant glycoprotein in peripheral nerve myelin and fulfills pivotal functions during myelin formation and maintenance. Mutations in the corresponding gene cause hereditary demyelinating neuropathies. In mice heterozygously deficient in P(0) (P(0)(+/-) mice), an established animal model for a subtype of hereditary neuropathies, T-lymphocytes are present in the demyelinating nerves. To monitor the possible involvement of the immune system in myelin pathology, we cross-bred P(0)(+/-) mice with null mutants for the recombination activating gene 1 (RAG-1) or with mice deficient in the T-cell receptor alpha-subunit. We found that in P(0)(+/-) mice myelin degeneration and impairment of nerve conduction properties is less severe when the immune system is deficient. Moreover, isolated T-lymphocytes from P(0)(+/-) mice show enhanced reactivity to myelin components of the peripheral nerve, such as P(0), P(2), and myelin basic protein. We hypothesize that autoreactive immune cells can significantly foster the demyelinating phenotype of mice with a primarily genetically based peripheral neuropathy.