Cell-mediated immunity to bovine P2 protein and neuritogenic synthetic peptide in experimental allergic neuritis

Cellular mRNA expression of interferon-gamma, IL-4 and transforming growth factor-beta (TGF-beta) by rat mononuclear cells stimulated with peripheral nerve myelin antigens in experimental allergic neuritis

Experimental allergic neuritis (EAN) serves as a useful model for inflammation in the peripheral nervous system. To study the potential role of important immunoregulatory and effector cytokines in EAN, we examined the expression of mRNA for interferon-gamma (IFN-gamma), IL-4 and TGF-beta by in situ hybridization in lymph node and splenic cells cultured with bovine peripheral nerve myelin (BPM), P2 and P0 during the course of EAN in Lewis rats. Levels of IFN-gamma mRNA-expressing mononuclear cells (MNC) from lymph nodes and spleens roughly correlated with clinical status, consistent with a disease-promoting role for IFN-gamma. BPM, P0 and P2-reactive IFN-gamma mRNA-expressing T cells appeared in lymph nodes and spleen before onset of the disease, whereas a significant TGF-beta response to BPM, P2 and P0 was observed at lower levels than the IFN-gamma response and at onset of recovery, consistent with a disease down-regulating role of TGF-beta. IL-4 mRNA-expressing cells were found at levels similar to TGF-beta mRNA-expressing cells, and with the latest peak of the three cytokines examined. This result suggests that IL-4 may also suppress IFN-gamma expression at late recovery phase of EAN.

Th1-like cell responses to peripheral nerve myelin components over the course of experimental allergic neuritis in Lewis rats

Experimental allergic neuritis (EAN) is a T cell-mediated animal model of Guillain-Barré syndrome characterized by inflammation and demyelination of peripheral nerves. EAN can be induced by immunization of rats with bovine peripheral nerve myelin (BPM) or the myelin proteins P2 or P0, but the extent of T cell responses over the course of EAN is incompletely defined. We studied the T cell responses to these proteins and the glycolipid GM1 by enumerating T helper type 1 (Th1)-like cells secreting interferon-gamma (IFN-gamma) after short-term culture of mononuclear cells (MNC) in presence of antigen. Already 7 days post immunization (p.i.) with BPM and before onset of clinical EAN, lymph nodes contained elevated levels of P2 responsive T cells. At the height of EAN on day 14 p.i. and during recovery, T cell levels responding to BPM, P0 and GM1 were also elevated. The same temporal profiles and specificities were registered for antigen reactive spleen MNC. The results implicate that Th1-like cells with multiple specificities including the glycolipid GM1 occur at increased levels in lymphoid organs in EAN rats, and that IFN-gamma may be an important effector molecule in the induction of nerve damage.

Activated T lymphocyte subsets in experimental allergic neuritis

Changes in activated T cell subsets in peripheral blood were examined during the course of experimental allergic neuritis (EAN), using two-color immunofluorescence flow cytometry. Both CD4+ and CD8+ activated T cells decreased transiently before the onset of clinical signs, and increased just around the time of onset of the disease. In contrast, during the recovery phase, the numbers of CD4+ activated T cells returned to the normal range, whereas CD8+ activated T cells continued to increase. These findings imply that activation of CD4+ helper/inducer cells contributes mainly to the evolution of EAN, and that of CD8+ suppressor cells are necessary for recovery.

T-cell and macrophage activation in experimental autoimmune neuritis and Guillain-Barré syndrome

Evidence implicating cellular immune responses in the pathogenesis of experimental autoimmune neuritis (EAN) and Guillain-Barré syndrome (GBS) is reviewed. In EAN the decisive role of T-lymphocytes in the initiation of immune-mediated nerve damage has been firmly established by adoptive transfer experiments. Macrophages but not Schwann cells express major histocompatibility complex class II gene products in situ and hence may function as antigen presenters. Macrophages are crucial in the amplification and effector phase and damage the myelin sheath by phagocytic attack and release of inflammatory mediators such as toxic oxygen radicals, arachidonic acid metabolites, complement, or hydrolases. Macrophage activation in EAN is achieved by interferon-gamma. Attempts to detect specific sensitization of T-lymphocytes to nerve antigens in patients with GBS have so far been unsuccessful. However, circulating activated T cells can be found in patients with GBS, as evidenced by augmented expression of HLA-DR antigen, the transferrin receptor, and the interleukin-2 receptor on the surface of peripheral blood T cells, and by increased serum concentrations of interleukin-2 and the soluble interleukin-2 receptor. In addition, we present data indicating macrophage activation in GBS.

Responsiveness to P2 of blood- and cauda equina-derived lymphocytes in experimental allergic neuritis in the Lewis rat: preliminary characterisation of a P2-specific cauda equina-derived T cell line

Experimental allergic neuritis (EAN) was induced in Lewis rats by immunisation with bovine spinal root myelin. Neurological signs appeared on day 12 and persisted for 10-15 days. A transient protein P2-specific proliferative response of circulating mononuclear cells was detected on days 10 and 14 after immunisation but not on days 17 and 35. Mononuclear cells recovered from cauda equina infiltrates on days 14 and 17 showed greater responsiveness to P2 than circulating cells. A P2-specific, interleukin-2-dependent T cell line has been developed from cauda equina (CE)-derived lymphocytes. In adoptive transfer experiments this cell line did not induce EAN but did protect normal recipients from actively induced EAN.

An approach to searching protein sequences for superfamily relationships or chance similarities relevant to the molecular mimicry hypothesis: application to the basic proteins of myelin

A rapid method for similarity searches (FASTP program) was used to identify similarities between a protein database and the human basic proteins from myelin [P2 protein and 17.2K, 18.5K, and 21.5K variants of myelin basic protein (MBP)]. From similarity scores, we concluded that none of the presently known proteins are in a family containing the MBPs. No new members were found for the lipid-binding family of which P2 is a member. Sequence similarities deemed relevant to the molecular mimicry hypothesis for virus-induced autoimmunity were identified in FASTP data with the aid of microcomputer programs. Several MBP/viral protein similarities were found that have not been reported previously. Of note because of their association with demyelinating conditions were proteins from visna and vaccinia. Similarity with visna was specific to the 21.5K and 20.2K MBPs. The most interesting new possibility for mimicry involving the P2 protein was between the influenza A NS2 protein and a sequence region of P2 thought to be neuritogenic in animals and mitogenic for lymphocytes from some patients with Guillain-Barré syndrome (GBS). This may have relevance for some cases of GBS associated with the 1976 U.S.A. swine flu vaccination program. Because FASTP reports only the best similarities between proteins, searches with FASTP may not have detected all the examples of mimicry present in the database. Searches might also be more effective if similarities could be scored on immunological rather than structural relatedness.

Immune responses in experimental allergic neuritis treated with corticosteroids

The preventive and suppressive effects of methylprednisolone (MP) were investigated in 22 rabbits immunized with peripheral nerve myelin. Cellular reactivity to bovine P2 protein (P2) and anti-P2 antibody were also examined serially in these animals, using the lymphocyte proliferation test or enzyme-linked immunosorbent assay. Seven animals (preventive group), given 15 mg/day of MP subcutaneously from Days 0-28, showed a significant reduction in maximal severity and a delay in onset in comparison with 8 control animals. The remaining 7 animals (suppressive group), given the same dose of MP from Days 11-28, also showed significantly milder clinical signs than those observed in the controls. However, cellular hypersensitivity to P2 were manifested at Day 14 (just after clinical onset) in the controls, as well as in the preventive or suppressive groups. Furthermore, anti-P2 antibody was detected in each group after Day 14. These results suggested that the interference of inflammatory processes of immune-mediated disease might respond to the preventive and suppressive effects of MP.