T cell subsets and Ia-positive cells in the sciatic nerve during the course of experimental allergic neuritis

Schwann cell differentiation inhibits interferon-gamma induction of expression of major histocompatibility complex class II and intercellular adhesion molecule-1

Interferon-gamma (IFN-γ) upregulates major histocompatibility complex class II (MHC class II) antigens and intercellular adhesion molecule-1 (ICAM-1) on Schwann cells (SC) in vitro, but in nerves of animals and patients MHC class II is primarily expressed on inflammatory cells. We investigated whether SC maturation influences their expression. IFN-γ induced MHC class II and upregulated ICAM-1; the axolemma-like signal 8-bromo cyclic adenosine monophosphate (8 Br cAMP) with IFN-γ inhibited expression. Delaying addition of 8 Br cAMP to SC already exposed to IFN-γ inhibited ongoing expression; addition of IFN-γ to SC already exposed to 8 Br cAMP resulted in minimal expression. Variability of cytokine-induced MHC class II and ICAM-1 expression by SC in vivo may represent the variability of signals from axolemma.

Expression and distribution of transcription factor NF-kappaB and inhibitor IkappaB in the inflamed peripheral nervous system

The NF-kappaB family of transcription factors is critically involved in the immune response. The activity of these proteins is under strict control of an inhibitory molecule called IkappaB. The present study investigated the expression and distribution pattern of NF-kappaB and IkappaB in sural nerve biopsies obtained from patients with Guillain-Barré syndrome, chronic inflammatory demyelinating polyradiculoneuropathy, and various non-inflammatory neuropathies. In inflammatory demyelinating as well as non-inflammatory neuropathies, NF-kappaB was primarily expressed by macrophages, as determined by immunohistochemistry. IkappaB, however, could be localized to macrophages as well as T cells in inflammatory demyelinating neuropathies, whereas in non-inflammatory controls Schwann cells were found to be the primary cell type expressing this inhibitor. Quantitation of immunoreactivity revealed a statistically significant increase of NF-kappaB expression in inflammatory demyelinating cases compared to controls. Our results suggest an important function of the NF-kappaB pool in the genesis of inflammatory demyelination in the peripheral nervous system.

Flow cytometric analysis of infiltrating cells in the peripheral nerves in experimental allergic neuritis

Experimental autoimmune neuritis (EAN) is an animal model that shares clinical, pathological and electrophysiological features with the human disease Guillain-Barré syndrome (GBS). In this study, we isolated and characterized by fluorescent activated cell sorter (FACS) phenotype of the inflammatory cells infiltrating cauda equina (CE) of Lewis rats at the active stage of the disease. We found that at this stage of EAN macrophages (Mphi) and alphabeta T cells were two major populations isolated from CE. We also found that among total cell population isolated from CE, gammadelta T and NK cells composed two small but distinct populations, while B cells were negligible. We characterized phenotype of alphabeta T cells in CE as CD45RC(+)CD8(+) (activated cytotoxic lymphocytes) and CD45RC(-)CD4(+) (memory Th cells). The phenotype of gammadelta T cells was found to be consisted of only CD45RC(+)CD8(+) cells. Both alphabeta and gammadelta T cells in CE expressed a higher level of CD25, CD44 and CD54 activation markers compared to the other tissues. Immunohistochemistry demonstrated that gammadelta T cells existed apart from the intense cellular infiltrate. This is the first report on the isolation and FACS analysis of CE-infiltrating cells, contributing a new and alternative approach to study the inflammatory lesions in EAN. We conclude that both alphabeta and gammadelta T cells have a unique activation/inflammatory phenotype required to traffic through and be retained in the peripheral nerves during EAN.

Disruption and reorganization of sodium channels in experimental allergic neuritis

The axonal distribution of voltage-dependent Na+ channels was determined during inflammatory demyelinating disease of the peripheral nervous system. Experimental allergic neuritis was induced in Lewis rats by active immunization. In diseased spinal roots Na+ channel immunofluorescence at many nodes of Ranvier changed from a highly focal ring to a more diffuse pattern and, as the disease progressed, eventually became undetectable. The loss of nodal channels corresponded closely with the development of clinical signs. Electrophysiological measurements and computations showed that a lateral spread of nodal Na+ channels could contribute significantly to temperature sensitivity and conduction block. During recovery new clusters of Na+ channels were seen. In fibers with large-scale demyelination, the new aggregates formed at the edges of adhering Schwann cells and appeared to fuse to form new nodes. At nodes with demyelination limited to paranodal retraction, Na+ channels were often found divided into two symmetric highly focal clusters. These results suggest that reorganization of Na+ channels plays an important role in the pathogenesis of demyelinating neuropathies.

Human autoimmune neuropathies

Peripheral nerve diseases are among the most prevalent disorders of the nervous system. Because of the accessibility of the peripheral nervous system (PNS) to direct physiological and pathological study, neuropathies have traditionally played a unique role in developing our understanding of basic mechanism of nervous system injury and repair. At present they are providing new insight into the mechanisms of immune injury to the nervous system. A rapidly growing catalogue of PNS disorders are now suspected to be immune-mediated, and in the best understood of these disorders, the molecular and cellular targets of immune attack are known, and the pathophysiology follows directly from the specific immune injury. This review summarizes the immunologically relevant features of the PNS, then considers selected immune-mediated neuropathies, focusing on pathogenetic mechanisms. Finally, the PNS is providing a testing ground for new immunotherapies and approaches to protection and regeneration, including the use of trophic factors. The current status of treatment and implications for future approaches is reviewed.

Pathogenicity of cilia-associated respiratory (CAR) bacillus isolates for F344, LEW, and SD rats

We conducted experiments to test whether rats of F344, LEW, and SD strains differ in susceptibility to mycoplasma-free isolates of cilia-associated respiratory (CAR) bacillus, whether Mycoplasma pulmonis can affect expression of CAR bacillus disease, and whether isolates of CAR bacillus differ in virulence for rats. In the first experiment, 24 rats of each strain were inoculated intranasally with 10(7) bacilli of CAR bacillus X1428D/AS, and 24 rats of each strain were inoculated with sterile medium (controls). Eight weeks later, eight inoculated rats and eight control rats of each strain were euthanatized, eight inoculated and eight control rats were given 10(6.5) colony-forming units of M. pulmonis X1428D, and eight inoculated rats and eight control rats were sham inoculated. Four rats of each group were euthanatized 4 or 8 weeks after the second inoculation. Severity of lesions in nasal passages, middle ear, trachea, and lungs was assessed by scoring. Rats of all three strains given CAR bacillus had typical lesions of similar severity; M. pulmonis X1428D was avirulent and did not exacerbate CAR bacillus disease. In the second experiment, groups of eight rats of F344 and SD strains were given 10(5) or 10(7) CAR bacillus X1328E, X1428D/AS, or X2450D and euthanatized 8 or 16 weeks later. Isolates X1428D/AS and X2450D caused similar lesions in rats of both strains and at both doses, but CAR bacillus X1328E was avirulent. Rats of the tested strains are similarly susceptible to CAR bacillus disease, but CAR bacillus isolates differ in virulence.

In vitro studies of glial cells: what can we learn about demyelinating diseases?

Acquired demyelinating diseases of the central and peripheral nervous systems comprise an important group of neurologic diseases of unknown etiology and incompletely understood pathogenesis. Cultures of glial cells are proving highly useful in investigating the role of both antibodies and cytokines in the pathogenesis of these disorders. While there clearly is need for comparative studies employing more complex systems and using patient derived tissues, glial cell cultures provide important advantages by allowing researchers to characterize the effect of cytokines and growth factors on specific cell types in controlled conditions.

Comparative severity of respiratory lesions of sialodacryoadenitis virus and Sendai virus infections in LEW and F344 rats

In several chronic diseases, lesions are more severe in LEW rats than in F344 rats. To determine whether or not acute viral diseases also are more severe in LEW rats than in F344 rats, we inoculated 6-7-week-old LEW and F344 rats with 10(7.2) cell culture infective units of sialodacryoadenitis virus or 10(4.7) infective units of Sendai virus. Twenty-four rats of each strain were given each virus. Lesions in nasal passages, tracheas, intrapulmonary airways, and pulmonary alveoli in 6 or 12 rats inoculated with each virus were assessed by scoring 5, 10, and 14 days after inoculation. Both viruses caused typical patchy necrotizing rhinitis, tracheitis, bronchitis, and bronchiolitis, with multifocal pneumonitis, in rats of both strains. Mean lesion indices for LEW rats given sialodacryoadenitis virus were significantly different from those for F344 rats for nasal passages on days 10 (0.999 vs. 0.680) and 14 (0.736 vs. 0.278), bronchi on day 5 (0.479 vs. 0.361), and alveoli on day 5 (0.677 vs. 0.275). Lesion indices for LEW rats given Sendai virus were significantly different from those for F344 rats for nasal passages on days 10 (1.000 vs. 0.611) and 14 (0.778 vs. 0.583); trachea on day 10 (0.625 vs. 0.028); bronchi on days 5 (0.476 vs. 0.331), 10 (0.123 vs. 0.013), and 14 (0.038 vs. 0); and alveoli on days 5 (0.413 vs. 0.114) and 10 (0.185 vs. 0.020). Thus, at the tested doses, both viruses caused more severe respiratory tract lesions in LEW rats than in F344 rats.

The beta 2-adrenergic agonist terbutaline suppresses experimental allergic neuritis in Lewis rats

Treatment of rats with experimental allergic neuritis with the beta 2-adrenergic agonist terbutaline suppresses clinical symptoms, decreases demyelination and Wallerian degeneration in peripheral nerves and improves electrophysiological parameters. Treatment is highly effective when given from the time of immunization through the acute phase of illness, when given for the first 12 days after immunization and also when given after the onset of the disease.

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.

Macrophages but not Schwann cells express Ia antigen in experimental autoimmune neuritis

This study was designed to identify which cells express major histocompatibility complex class II (Ia) antigen in experimental autoimmune neuritis and may therefore be antigen presenters. Serial 1-micron-thick cryosections of ventral roots of animals with experimental autoimmune neuritis were labeled with Ox6 antibody against rat Ia, the ED1 antibody to identify monocytes/macrophages and an antiserum against S100, a marker for Schwann cells. Ia-positive cells were predominantly present before overt clinical signs and demyelination (day 12). At later stages when many axons were demyelinated, their number was markedly reduced. Few Ia-positive cells that had extending long processes, which over some distance were in immediate contact with several myelin sheaths, were scattered in normal-appearing nerve roots at these later time points. Most of the Ia-positive cells could be identified as ED1-positive lean monocytes/macrophages, but in contrast most phagocytic macrophages in advanced stages of myelin degradation no longer expressed Ia. Ia-positive structures were invariably negative for S100 at early and late stages of experimental autoimmune neuritis, indicating that Schwann cells did not express identifiable Ia antigen. These findings contrast with reports of expression of major histocompatibility complex class II antigens by Schwann cells in human neuropathies. Furthermore they do not support the notion that aberrant Ia expression by Schwann cells plays a major pathogenic role in experimental autoimmune disease of the peripheral nervous system.

Quantitative analysis of endoneurial T-cells in human sural nerve biopsies

We used immunocytochemical methods on sural nerve biopsies from 42 patients with peripheral neuropathy to identify mononuclear cells, determine whether lymphocytic infiltration occurs in a variety of neuropathies, and identify the subtypes of lymphocytes. Immunostained cells were present in 76% of nerve biopsies. CD3+ cells (T lymphocytes) were greatest in density (cells/mm2). In patients whose CD4:CD8 T cell ratio was measured also in blood and cerebrospinal fluid, the CD4:CD8 T cell ratio was similar in all three compartments. These findings suggest that T lymphocytes are frequently present in nerves obtained from patients with various types of neuropathies and raise questions about factors that attract T lymphocytes into nerve that may be important in pathogenesis.

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.

Role of endoneural cells in experimental allergic neuritis and characterisation of a resident phagocytic cell

Electrophysiological, clinical and histological techniques were used to monitor the time course of events related to experimental allergic neuritis (EAN) in 48 Lewis rats. The primary lesion was found to be paranodal demyelination without cellular infiltration. Endoneural phagocytes derive from hematogenous ED1+ED2- monocytes and possibly from resident ED1-ED2+ monocytic cells, not from Schwann cells and fibroblasts. We demonstrate a population of monocytic Ia-bearing, ED1-ED2+ spindle-shaped cells residing in normal peripheral nerve and provide evidence for their transformation into macrophages in the course of EAN.

Major histocompatibility antigens and lymphocyte subsets during experimental allergic neuritis in the Lewis rat

Major histocompatibility antigens were identified in frozen sections of normal Lewis rat peripheral nerve tissue with monoclonal antibodies and an avidin-biotin-peroxidase complex system. Class I antigen is normally required for cytotoxic/suppressor T lymphocyte function and class II antigen for activation of helper T lymphocytes. In the sciatic nerves class I antigen was expressed diffusely by most endoneurial and perineurial cells but class II antigen only by a minority. In the cauda equina class I antigen was expressed by all arachnoid and some endoneurial cells, while class II antigen was expressed by a smaller proportion of arachnoid cells in the endoneurium of spinal roots and interstitial cells surrounding dorsal root ganglion neurons. The endothelium of endoneurial, perineurial and meningeal vessels uniformly expressed class I but not class II antigen. Experimental allergic neuritis was induced in Lewis rats by immunisation with bovine intradural root myelin. Early lesions consisted of multifocal infiltration of the nerve roots by cells expressing leucocyte common antigen. Surrounding endoneurial cells showed markedly increased expression of major histocompatibility antigens. In inflammatory lesions about 10% of the cells were stained with pan T cell antibodies. T lymphocyte subsets were identified with antibody W3/25 for helper cells and MRC OX-8 for cytotoxic/suppressor cells. The W3/25 positive cells were usually slightly in excess of OX-8 positive cells and their relative proportions did not alter during the disease. The presence of class I antigen on normal endothelium and its increased expression on endoneurial cells in the early phase of inflammation suggest an important role for class I restricted lymphocytes in the pathogenesis of the early stages of experimental allergic neuritis.