Cellular hypersensitivity to basic myelin (P2) protein in the Guillain-Barré syndrome

The Neuroimmunology of Guillain-Barré Syndrome and the Potential Role of an Aging Immune System

Guillain-Barré syndrome (GBS) is a paralyzing autoimmune condition affecting the peripheral nervous system (PNS). Within GBS there are several variants affecting different aspects of the peripheral nerve. In general, there appears to be a role for T cells, macrophages, B cells, and complement in initiating and perpetuating attacks on gangliosides of Schwann cells and axons. Of note, GBS has an increased prevalence and severity with increasing age. In addition, there are alterations in immune cell functioning that may play a role in differences in GBS with age alongside general age-related declines in reparative processes (e.g., delayed de-differentiation of Schwann cells and decline in phagocytic ability of macrophages). The present review will explore the immune response in GBS as well as in animal models of several variants of the disorder. In addition, the potential involvement of an aging immune system in contributing to the increased prevalence and severity of GBS with age will be theorized.

Molecular mimicry and the autoimmune response to the peripheral nerve myelin P0 glycoprotein

In the Lewis rat immunisation with the myelin P0 glycoprotein can induce an inflammatory demyelinating disease of the peripheral nervous system, experimental allergic neuritis (EAN), which has many clinical and histopathological parallels with the human disease the Guillain-Barre syndrome. In view of the reported association of GBS with a number of infectious agents we have investigated whether "molecular mimicry" may occur between microbial antigens and the P0 protein that could possibly trigger a similar pathogenic autoimmune response in man. A computer search of the available protein sequence data bases identified several absolute sequence homologies between P0 and viral proteins that involve five or more consecutive amino acid residues. Four of these sequence homologies involved viral pathogens previously associated with the Guillain-Barre syndrome, namely Epstein-Barr virus (EBV), cytomegalovirus (CMV), Varicella zoster virus (VZV) and human immunodeficiency virus I (HIV I). Although, sequence homologies were also found between viral peptides and the neuritogenic determinants of P0, residues 56-71 and 180-199, these homologies proved incapable of eliciting EAN in the Lewis rat. These observations are discussed with reference to the role that molecular mimicry between T cell epitopes on pathogen derived antigens and the P0 protein may play in the pathogenesis of the Guillain-Barre syndrome.

Cell adhesion molecules of the immunoglobulin supergene family as tissue-specific autoantigens: induction of experimental allergic neuritis (EAN) by P0 protein-specific T cell lines

The P0 glycoprotein is a homophilic cell adhesion molecule of the immunoglobulin supergene family which is responsible for maintaining the structure of compact internodal myelin in the peripheral nervous system (PNS). Utilizing a panel of synthetic P0 peptides two distinct T cell epitopes have been identified that can induce T cell-mediated experimental autoimmune neuritis (EAN) in the Lewis rat. One T cell epitope (amino acid residues 56-71), is located within the extracellular, immunoglobulin-like domain of P0, while the other disease-inducing T cell epitope (residues 180-199) is located within the proteins cytoplasmic carboxyterminal domain. The adoptive transfer of 10(6) CD4+ T line cells specific for either of these peptide antigens induced EAN in syngeneic recipients. However, while the pathogenic response induced by both peptide-specific T cell lines was identical, their epitopes differ markedly in their immunologic properties in vivo. In particular while the response to peptide p180-199 was immunodominant in animals immunized with either purified P0 protein or the native membrane-bound P0 protein in autologous rat peripheral nerve myelin, no response to peptide p56-71 was detected, indicating that this epitope is cryptic. This study provides the first experimental evidence that the immunoglobulin-like domains of members of the immunoglobulin supergene family can function as target autoantigens in T cell-mediated autoimmune disease.

P2 specific lymphocyte transformation in Guillain-Barré syndrome and chronic idiopathic demyelinating polyradiculoneuropathy

Thymidine incorporation proliferation assays to whole bovine P2 protein and its 58-81 and 14-25 synthetic peptides were performed on blood mononuclear cells from ten patients with Guillain-Barré syndrome (GBS), six patients with chronic idiopathic demyelinating polyradiculoneuropathy (CIDP), and age and sex matched normal subjects. The only patients whose cells showed any response were two out of four with very early GBS. One responded to P2 and both synthetic peptides. One responded to P2 but to neither peptide. The results support a role for cell mediated immunity to P2 protein in some patients with Guillain-Barré syndrome.

Proximal motor neuropathy, IgA paraproteinaemia and anti-myelin-associated glycoprotein reactivity

We report a case with proximal motor neuropathy associated with benign IgA lambda paraproteinaemia. Immunoblot demonstrated reactivity to myelin-associated glycoprotein and not to P2 protein of peripheral nerve. Dramatic improvement of the polyneuropathy was observed with steroid treatment alone within 4 weeks.

T lymphocyte activation antigens in Guillain-Barré syndrome and chronic idiopathic demyelinating polyradiculoneuropathy

Activated circulating T lymphocytes were measured in ten patients with Guillain-Barré syndrome (GBS) and in ten with chronic idiopathic demyelinating polyradiculoneuropathy (CIDP), each paired with an age- and sex-matched healthy control. Activated T cells were identified by double labelling with phycoerythrin-conjugated anti-CD3 antibody and biotinylated antibodies to activation antigens: human leucocyte antigen (HLA)-DR, transferrin receptor (TFR) or interleukin-2 receptor (IL-2R) visualised with an avidin-biotin-fluorescein system. The frequency of activated T cells was increased in the GBS group. The median of the DR-positive T cells in the patients was 3.4% (range 0.5-9.4%), compared with 1.4% (range 0-4.3%) in the controls (P less than 0.01). For TFR the corresponding medians were 3.3% (range 0.5-6.2%) in the patients and 0% (range 0-2.5%) in the controls (P less than 0.01), and for IL-2R 3.7% (range 0-6.0%) in the patients compared with 0% (range 0-2.9%) in the controls (P less than 0.01). In the CIDP group the median percentage of activated T cells was also increased but the differences were less significant: for DR, patients 2.4% (range 0-3.8%), controls 0.5% (range 0-2.0%, P less than 0.05); for TFR, patients 0% (range 0-5.3%), controls 0% (range 0-1.0%, not significant), and for IL-2R, patients 0% (range 0-2.5%), controls 0% (range 0-0.5%, not significant). The activated cells might be directed against microbial antigens encountered during the infection preceding GBS, autoantigens, bacterial antigens encountered during concurrent infection, or a combination of these.

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

Cellular reactivity to bovine P2 protein (P2) and its two synthetic peptides, SP66-78 and SP70-78, was serially examined by the lymphocyte proliferation test in animals with experimental allergic neuritis (EAN). SP66-78 and SP70-78 correspond to residues 66-78 and 70-78 of bovine P2. Proliferative response to SP66-78 as well as P2 appeared at day 7 before the onset of EAN and was clearly manifested at day 14 in the active stage, thereafter disappearing in the stable stage, whereas no response to SP70-78 was detected during the course of the disease. These results suggest that cell-mediated immune response to P2 and the specific part residues 66-78 of P2 play an important role in the pathogenesis of EAN.

Cellular hypersensitivity to nervous antigens in Guillain-Barré syndrome

Cell-mediated immune responses to various nervous antigens were examined in 12 cases of Guillain-Barré syndrome (GBS), 24 cases of noninflammatory peripheral neuropathy (NIPN), and 18 cases of degenerative disorders of central nervous system (CNSDD), using the lymphocyte-transformation technique. Cellular hypersensitivity to bovine P2 protein (P2) and a synthetic peptide, SP66-78, corresponding to the residues 66-78 of P2, was detected in about two-thirds of GBS cases, especially in the active or improving stages, but not in NIPN and CNSDD. The lymphocytes sensitized to these nervous antigens might play an important role in the pathogenesis of GBS.

Isolation of P2 protein--reactive T-cell lines from human blood

Human T-cell lines reactive with the peripheral nerve myelin protein, P2 protein, were isolated from the peripheral blood of 4 normal persons and 1 patient with Guillain-Barré syndrome. These predominantly helper phenotype T-cell lines were isolated and maintained in vitro by antigen stimulation followed by culture with interleukin 2. Myelin basic protein-reactive T cells were also isolated in parallel from the same subjects as antigen specificity controls. T cells recognizing myelin basic protein did not respond to P2 protein, nor did P2-reactive cells respond to myelin basic protein. These findings suggest that a potential for autoimmune reactivity with peripheral nervous system myelin antigens may exist for both normal persons and some patients with neurological disease.

Macrophage procoagulant activity as a measure of cell-mediated immunity to P2 protein of peripheral nerves in the Guillain-Barré syndrome

Cell-mediated and humoral immunity to purified nerve proteins has been assessed in GBS patients and compared with that of patients with other neurological diseases and healthy controls. A strong and specific cell-mediated response to the neuritogenic basic protein P2 occurred in 13/16 GBS patients tested. Extremely low levels of P2 (0.01 micrograms/culture) induced monocyte/macrophage procoagulant activity (MPCA) on peripheral blood mononuclear cells (PBM) from GBS patients (P = 0.007) whereas higher concentrations (2 micrograms/culture) of myelin basic protein (MBP) and sciatic nerve myelin (SNM) were required to stimulate similar levels of activity. These concentrations of nerve antigens failed to induce significant MPCA on peripheral blood mononuclear cells of patients with other neuropathies or healthy controls. Lipopolysaccharide, a non-specific stimulant of macrophage procoagulant activity, induced similar procoagulant levels on PBM from each group. The MPCA assay was a sensitive, quantitative and specific indicator of cell-mediated immunity to the neuritogenic peptide, P2 in GBS patients. Serum antibodies to P2, P0 and SNM were detected by a sensitive solid-phase radioimmunoassay. Naturally occurring antibodies to peripheral nerve antigens were observed in sera of healthy subjects and these levels were not significantly different from patients with GBS or those with other neuropathies. Our results indicate that the autoimmune cell-mediated response to the neuritogenic peptide P2 plays a major role in the pathogenesis of GBS.

Peripheral nerve P2 basic protein and the Guillain-Barré syndrome. In vitro demonstration of P2-specific antibody-secreting cells

An immune response to the peripheral nerve basic protein P2 may be operative in the pathogenesis of the Guillain-Barré syndrome (GBS). A method is described for the purification of P2 of human origin. Purified P2 was used to investigate whether lymphocytes derived from peripheral blood of GBS patients are capable of producing P2-specific antibodies after stimulation with the antigen in vitro. Peripheral blood lymphocytes (PBL) from 5 GBS patients, from 3 patients with chronic idiopathic polyradiculoneuropathy (CIP) and from 3 normal controls were cultured in vitro in the presence of P2. PBL from the 5 GBS patients were shown to generate an antigen (P2)-specific antibody response. Contrariwise, PBL from the 3 CIP patients as well as from the 3 normal controls did not show this specific response.

Immune responses to myelin antigens in Guillain-Barré syndrome

Antibodies to nerve antigens were sought in the sera of 17 patients with acute Guillain-Barré syndrome (GBS), 11 with chronic relapsing demyelinating poly-radiculoneuropathy (CRP), 20 with other neuropathies (ON), 15 with other neurological diseases (OND) and 19 normal subjects. Complement-fixing antibodies to a suspension of human peripheral nerve tissue were identified in only 2 patients with GBS and 1 with chronic progressive neuropathy. Five GBS sera gave complement fixation reactions with rabbit sciatic nerve. The sera were also tested for galactocerebroside (Gal-C) binding activity using a solid phase assay. The range of values in all groups was the same, although the mean values for patients with GBS, ON and OND were higher than those of normal subjects. In a radioimmunoassay for antibodies to bovine P2 slightly more radiolabelled antigen was precipitated by the GBS group of sera than by sera from the other groups, but only one serum from the GBS and another from the CRP patients precipitated more than 10% of the label. Addition of bovine P2 to cultures of peripheral blood mononuclear cells from 11 patients with GBS did not cause significant stimulation. Immunoassay for antibody to myelin basic protein (MBP) showed an increased proportion of sera with low binding activity in the GBS and CRP groups. The results suggest that humoral immune responses to potentially neuritogenic antigens are found with marginally increased frequency in patients with GBS and CRP.

Spontaneous and experimental neuritis and the distribution of the myelin protein P2 in the nervous system

The P2 contents of nervous tissues from the human, rabbit, guinea pig, and Lewis rat were measured by radioimmunoassay. The ventral spinal roots contained more P2 than any other tissue. Human dorsal roots and peripheral nerves contained 41-65% of the amount in human ventral roots. Human olfactory and optic nerves and brain contained 1.1-2.7%, spinal cord, 2.8%, cranial nerve VIII, 11%, and cerebral grey matter, 0%. The relative amounts in the rabbit nervous system were similar except that the spinal cord contained 20% of the amount in the ventral roots. Qualitative estimates in the guinea pig showed that the spinal roots and peripheral nerves contained more P2 than the spinal cord, and that none was present in the brain. In the Lewis rat, P2 could be detected in the spinal roots and peripheral nerves but not in the CNS. The distribution of P2 in the human nervous system parallels the incidence and severity of lesions in acute polyradiculoneuritis. It also explains the absence of any lesions in the CNS when experimental allergic neuritis is induced in the Lewis rat.

Abnormal serum factors in Guillain-Barré syndrome

The Guillain-Barré Syndrome (GBS) is generally considered to be a cell-mediated immunopathologic disease of the peripheral nervous system (PNS), although the evidence for this is indirect. Both in vitro and in vivo studies of sera from experimental animals with autoimmune demyelinating neuropathies suggest that serum factors, including antibodies to PNS myelin and/or Schwann cells, may be important in the pathogenesis of some of these disorders. More recently, similar in vitro and in vivo techniques, including the production of demyelination following intraneural injection in the rat have been employed to study sera from patients with GBS. The results of these studies demonstrate the presence of factor(s), as yet not fully characterized, that may be important in mediating demyelination. Moreover, in some patients with chronic or relapsing demyelinative inflammatory neuropathies and monoclonal gammopathy, there is evidence of antimyelin antibodies to PNS myelin. Further studies of serum from patients with acute GBS and these other neuropathies may clarify the role of serum factors in acquired inflammatory diseases of the PNS.

The treatment of chronic relapsing and chronic progressive idiopathic inflammatory polyneuropathy by plasma exchange

Observations are reported on the effects of plasma exchange on three patients with chronic relapsing idiopathic inflammatory polyneuropathy and three with the chronic progressive form of this disorder. Substantial temporary improvement occurred in two of the chronic relapsing cases in relation to repeated plasma exchanges, but only slight improvement in the remainder. A striking feature was the rapidity of the effect in the patients that improved. The significance of these observations in relation to pathogenesis and to clinical management of the disorder is discussed.

Immune responses in experimental allergic neuritis

The antibody and cell mediated immune responses were investigated in inbred Lewis rats with experimental allergic neuritis (EAN) induced by either P2, a protein purified from the bovine cauda equina nerve roots, or whole bovine nerve root myelin. In the P2 immunised animals both antibodies to P2 detected by radioimmunoassay and cell-mediated immunity to P2 assayed by skin testing appeared before the onset of EAN and persisted during and after the disease. In the myelin immunised animals the antibody titres were lower and somewhat delayed and the skin tests became negative at the height of the disease. Complement-fixing antibodies to galactocerebroside, which have been implicated in the production of demyelination under some circumstances, could not be detected in the serum after immunisation with either P2 or myelin. EAN was transferred passively with lymph node cells from rats immunised with either P2 or myelin although anti-P2 antibodies could not be detected in the serum of recipients with EAN. The results favour a cell-mediated immune response to P2 as the most important pathogenetic mechanism in EAN induced wtih whole myelin in the rat.

Cell-mediated immunity in idiopathic polyneuritis

The role of cell-mediated immunity (CMI) in the pathogenesis of idiopathic polyneuritis (IP) is discussed. Of significance has been the finding of a decreased suppressor T cell response in IP. This may provide an important common denominator linking the numerous antecedent events which trigger IP to the disease. The role of humoral immunity in IP and chronic relapsing inflammatory polyneuritis (CRIP) remains controversial, but has awakened renewed interest in view of recent reports of favorable response to plasmapheresis in IP and CRIP patients. P2 protein is an important neuritogenic factor in experimental allergic neuritis (EAN), but we failed to find antibody directed against P2 in either IP or CRIP even though anti-P2 antibody was regularly detected in EAN. Whether CMI response to P2 occurs in IP or CRIP remains controversial. We did not detect CMI response to P2 in IP or CRIP. It may be that the neuritogenic factor (or factors) in IP and CRIP remains to be found.

Detection of antibodies to central nervous system antigens by solid phase radioimmunoassay

A solid phase radioimmunoassay is described which employs 125I-protein-A to detect the presence of antibodies against a panel of cellular and soluble central nervous system (CNS) specific antigens coated onto polyvinylchloride Microtiter plates. Serum antibodies from rabbits immunized against myelin, myelin basic protein (MBP), glial acidic fibrillary protein (GFAP), astroglioma cells, and cerebellar cells were easily detected, and high specificity for each antiserum and antigen was also demonstrable. The assay is applicable to cerebrospinal fluid (CSF) from patients with neurological diseases to detect antibodies against CNS-specific antigens. The assay should be useful for examining cell lines derived from CNS tissue for the presence of brain proteins.

Peptides and autoimmune disease

The use of derived and synthetic peptides has contributed greatly to our understanding of encephalitogenic determinants in the basic protein molecule. Peptides derived from BP by use of trypsin, pepsin, cathepsin D (brain and liver) and BNPS-skatole have proven most useful. Synthetic peptides have served to define the disease-inducing determinants with precision. A remarkable feature of these studies is that different antigenic determinants serve as encephalitogenic sites in different species. The encephalitogenic sites comprise short peptide domains of the BP polypeptide chain, only 8 residues (rat), 9 residues (guinea pig), and 10 residues (rabbit) in length. In view of the requirement for both haptenic and carrier specificity of an immunogenic molecule, it is impressive that these peptides themselves elicit the autoimmune disease, EAE. While less active than BP on a molar basis, they are nonetheless potent encephalitogens, producing clinical signs in rats and guinea pigs at less than 1 microgram dose. The data indicate that for most animal species (guinea pig, rat, monkey) there appears to be only one major encephalitogenic determinant, an unusual finding in view of the number of antigenic determinants for cell-mediated immunity existing in the BP molecule. Possibly a combination of genetic and anatomical factors may account for this phenomenon. A relationship may exist between multiple sclerosis and EAE as shown by peptide studies; lymphocytes are found in MS patients during exacerbation sensitized to the same region of BP active in the monkey. The major encephalitogenic sites are: Guinea Pig (9) Phe-Ser-Trp-Gly-Ala-Glu-Gly-Gln-Lys(Arg); Rabbit (10) Thr-Thr-His-Tyr-Gly-Ser-Leu-Pro-Gln-Lys; Rat (8) Ser-Gln-Arg-Ser-Gln-Asp-Glu-Asn; Monkey (14) Phe-Lys-Leu-Gly-Gly-Arg-Asp-Ser-Arg-Ser-Gly-Ser-Pro-Hser.

The autoimmune features of acute transverse myelopathy

Lymphocytes from patients with acute transverse myelopathy (ATM) were shown to undergo a specific and significant transformation when cultured in vitro in the presence of either the central nervous myelin basic encephalitogenic protein (BE) or the peripheral nerve myelin P2 protein. A similar pattern of response was demonstrated in acute disseminated encephalomyelitis and in acute myeloradiculitis. Lymphocytes from patients suffering from other autoimmune neurological disorders or other neurological diseases affecting the spinal cord showed no response to there immunologically related antigens, which have previously been found to have the capacity of inducing experimental allergic encephalomyelitis, either alone or with experimental allergic neuritis, when injected into animals. The specific in vitro response to BE and P2 suggests that in vivo sensitization of lymphocytes to such self-antigens occurs in ATM and than a cell-mediated, probably postinfecious autoimmune mechanism may be an important factor in the pathogenesis of the disease.