Development of a major histocompatibility complex class II conditional knockout mouse to study cell-specific and time-dependent adaptive immune responses in peripheral nerves.

INTRODUCTION/AIMS: The precise relationship between molecular mimicry and tissue-specific autoimmunity is unknown. Major histocompatibility complex (MHC) class II antigen presenting cell-CD4+ T-cell receptor complex interactions are necessary for adaptive immunity. This study aimed to determine the role of endoneurial endothelial cell MHC class II in autoimmune polyneuropathy. METHODS: Cryopreserved Guillain-Barré syndrome (GBS) patient sural nerve biopsies and sciatic nerves from the severe murine experimental autoimmune neuritis (sm-EAN) GBS model were studied. Cultured conditional ready MHC Class II antigen A-alpha chain (H2-Aa) embryonic stem cells were used to generate H2-Aaflox/+ C57BL/6 mice. Mice were backcrossed and intercrossed to the SJL background to generate H2-Aaflox/flox SJL mice, bred with hemizygous Tamoxifen-inducible von Willebrand factor Cre recombinase (vWF-iCre/+) SJL mice to generate H2-Aaflox/flox; vWF-iCre/+ mice to study microvascular endothelial cell adaptive immune responses. Sm-EAN was induced in Tamoxifen-treated H2-Aaflox/flox; vWF-iCre/+, H2-Aaflox/flox; +/+, H2-Aa+/+; vWF-iCre/+ and untreated H2-Aaflox/flox; vWF-iCre/+ adult female SJL mice. Neurobehavioral, electrophysiological and histopathological assessments were performed at predefined time points. RESULTS: Endoneurial endothelial cell MHC class II expression was observed in normal and inflamed human and mouse peripheral nerves. Tamoxifen-treated H2-Aaflox/flox; vWF-iCre/+ mice were resistant to sm-EAN despite extensive MHC class II expression in lymphoid and non-lymphoid tissues. DISCUSSION: A conditional MHC class II knockout mouse to study cell- and time-dependent adaptive immune responses in vivo was developed. Initial studies show microvascular endothelial cell MHC class II expression is necessary for peripheral nerve specific autoimmunity, as advocated by human in vitro adaptive immunity and ex vivo transplant rejection studies.

Aberrant Expression of Nodal and Paranodal Molecules in Neuropathy Associated With IgM Monoclonal Gammopathy With Anti-Myelin-Associated Glycoprotein Antibodies.

To clarify the pathogenesis of anti-myelin-associated glycoprotein (MAG) antibody neuropathy associated with IgM monoclonal gammopathy (anti-MAG neuropathy), sural nerve biopsy specimens from 15 patients were investigated. Sodium channels, potassium channels, contactin-associated protein 1 (Caspr1), contactin 1, and neurofascin were evaluated by immunofluorescence in teased-fiber preparations. Immunoreactivity to the pan-sodium channel in both anti-MAG neuropathy patients and in normal controls was concentrated at the node of Ranvier unless there was demyelination, which was defined as the widening of the node of Ranvier. However, this immunoreactivity became weak or disappeared as demyelination progressed. In contrast, KCNQ2 immunostaining was nearly absent even in the absence of demyelination. The lengths of Caspr1, contactin 1, and pan-neurofascin immunostaining sites at the paranode were significantly increased compared with those of normal controls despite the absence of demyelination. The length of paranodal neurofascin staining correlated with the anti-MAG antibody titer, nerve conduction indices, the frequency of de/remyelination in teased-fiber preparations, and the frequency of widely spaced myelin (p < 0.05, p < 0.05, p < 0.01, and <0.05, respectively). These findings suggest that nodal and paranodal molecular alterations occur in early stages preceding the morphological changes associated with demyelination in anti-MAG neuropathy.

Paranodal dissection in chronic inflammatory demyelinating polyneuropathy with anti-neurofascin-155 and anti-contactin-1 antibodies.

OBJECTIVE: To investigate the morphological features of chronic inflammatory demyelinating polyneuropathy (CIDP) with autoantibodies directed against paranodal junctional molecules, particularly focusing on the fine structures of the paranodes. METHODS: We assessed sural nerve biopsy specimens obtained from 9 patients with CIDP with anti-neurofascin-155 antibodies and 1 patient with anti-contactin-1 antibodies. 13 patients with CIDP without these antibodies were also examined to compare pathological findings. RESULTS: Characteristic light and electron microscopy findings in transverse sections from patients with anti-neurofascin-155 and anti-contactin-1 antibodies indicated a slight reduction in myelinated fibre density, with scattered myelin ovoids, and the absence of macrophage-mediated demyelination or onion bulbs. Teased-fibre preparations revealed that segmental demyelination tended to be found in patients with relatively higher frequencies of axonal degeneration and was tandemly found at consecutive nodes of Ranvier in a single fibre. Assessment of longitudinal sections by electron microscopy revealed that detachment of terminal myelin loops from the axolemma was frequently found at the paranode in patients with anti-neurofascin-155 and anti-contactin-1 antibody-positive CIDP compared with patients with antibody-negative CIDP. Patients with anti-neurofascin-155 antibodies showed a positive correlation between the frequencies of axo-glial detachment at the paranode and axonal degeneration, as assessed by teased-fibre preparations (p<0.05). CONCLUSIONS: Paranodal dissection without classical macrophage-mediated demyelination is the characteristic feature of patients with CIDP with autoantibodies to paranodal axo-glial junctional molecules.

Endoneurial edema in sural nerve may indicate recent onset inflammatory neuropathy.

INTRODUCTION: Sural nerve biopsy is an important means of establishing the diagnosis of inflammatory neuropathies. We investigated the diagnostic value of endoneurial edema. METHODS: Diagnostic sural nerve biopsies from 42 patients with inflammatory and 28 patients with noninflammatory neuropathies were re-evaluated for the presence of endoneurial edema. Edema was assessed on hematoxylin-eosin stained paraffin and frozen sections and on azure II-methylene blue stained semithin sections. We determined the area of endoneurial edema on digitized images in relation to the entire endoneurial area of each fascicle. RESULTS: Edema was more extensive in neuropathies with short disease duration (≤12 months) as compared to long duration (>12 months; P < 0.01). Edema in inflammatory neuropathies of ≤12 months duration covered a larger area than in noninflammatory neuropathies (P < 0.01), and the extent of edema correlated negatively with disease duration (P < 0.05). CONCLUSIONS: Endoneurial edema may be a useful additional disease marker in inflammatory neuropathies of recent onset.

Gene expression profiling in nerve biopsy of vasculitic neuropathy.

To investigate molecular mechanisms of peripheral nerve vasculitis, gene expression patterns in archived frozen sural nerve biopsies from patients with vasculitic neuropathy were compared to control nerves by DNA microarray technology. There was a striking upregulation of mRNA of genes involved in immune system processes. Of special interest was the activation of immunoglobulin genes, such as IGLJ3, IGHG3, IGKC, and IGL, and of several chemokines, such as CXCL9 or CCR2. Genes involved in vascular proliferation or remodelling such as CXC31 and AIF were also upregulated. Among the downregulated genes were the Krüppel-Like Transcription Factors KLF2, KLF4 and the nuclear orphan receptor NR4A1 genes known to be involved in endothelial cell activation. Thus, this gene expression profile analysis revealed that in peripheral nerve vasculitis a prominent activation of immune response related genes as well as genes involved in vascular proliferation is taken place, while genes inhibiting endothelial cell activation are down regulated. These data point to interesting mechanistic clues to the molecular pathogenesis of vasculitic neuropathies.

Skin biopsy as an additional diagnostic tool in non-systemic vasculitic neuropathy.

Sural nerve biopsy is considered mandatory for diagnosing non-systemic vasculitic neuropathy (NSVN). This invasive technique may be associated with unpleasant sequelae and cannot easily be repeated. Skin punch biopsy from an affected area may be a less invasive and repeatable diagnostic method. Here we assessed the potential diagnostic value of skin punch biopsies in NSVN by analyzing skin biopsies in 20 patients with sural nerve biopsy-proven NSVN and in 11 patients with non-inflammatory axonal neuropathy. As further controls, skin biopsies were studied in nine healthy volunteers. Five millimeter skin punch biopsies were taken under local anesthesia from the distal lateral calf and T cells and macrophages were quantified after immunostaining. The diagnostic sensitivity and specificity compared to sural nerve biopsy was determined using receiver operating characteristic (ROC) analysis. ROC analysis revealed that the highest sensitivity (94%) and specificity (79%) for NSVN was obtained when perivascular macrophages were quantified. Quantification of scattered T cells yielded a sensitivity and specificity of 65%. Inflammatory cells were very rare in controls. Quantification of inflammatory cells in skin biopsies may thus be a sensitive and specific additional tool for diagnosing NSVN.

Antibodies to myelin-associated glycoprotein (anti-Mag) in IgM amyloidosis may influence expression of neuropathy in rare patients.

We have examined whether antibodies to myelin-associated glycoprotein (anti-MAG) influence neuropathy occurrence and phenotype in primary (AL IgM) amyloidosis. Anti-MAG and the cross-reacted sulfoglucuronyl paragloboside antibodies (SGPG) were studied in 46 patients with IgM amyloidosis (21 with polyneuropathy), and 21 matched IgM MGUS (monoclonal gammopathies of undetermined significance) controls without neuropathy. We assessed the occurrence, phenotype of neuropathy, and attributes of nerve conduction and their relation to antibody activity. Twenty of 46 patients with IgM amyloidosis (7 with and 13 without polyneuropathy) had elevation of anti-MAG or SGPG by enzyme-linked immunosorbent assay (ELISA). Two of the polyneuropathy patients with IgM amyloidosis had antibodies to MAG based on Western blot (WB) positivity. One of these patients, with the highest anti-MAG titer, had a painful sensory ataxia, with prominent demyelination, and amyloid deposition in sural nerve. The other anti-MAG WB-positive amyloid patient had an axonal neuropathy and dysautonomia. Low levels of anti-MAG antibodies were found in 12 of 21 IgM MGUS controls without neuropathy (mean follow-up, 11 years). We conclude that finding serum anti-MAG antibodies does not exclude the diagnosis of primary amyloidosis. They do not appear to affect the occurrence or expression of polyneuropathy, except possibly in occasional cases with WB positivity.

Case of mononeuritis multiplex onset with rituximab therapy for Waldenström's macroglobulinemia.

Waldenström's macroglobulinemia (WM) is a lymphoplasmacytic disorder with associated monoclonal gammopathy. A wide variety of neuropathies can be associated with WM, but most commonly it is a mild length-dependent sensory neuropathy of unclear etiology. Rituximab is a monoclonal antibody which suppresses mature B-cell populations. It has increasingly been used in wide applications including WM, especially in those cases with severe neuropathy. The highlighted case provides an example of rituximab treatment complication in a WM patient with mild sensory neuropathy that evolved to multiple mononeuropathies with features of systemic vasculitis and unusual conversion of type I to type II cryoglobulinemia.

Severe cranial nerve involvement in a patient with monoclonal anti-MAG/SGPG IgM antibody and localized hard palate amyloidosis.

We report a patient with severe cranial polyneuropathy as well as sensory limb neuropathy. Biclonal serum IgM-kappa/IgM-lambda gammopathy was found and serum anti-myelin-associated glycoprotein (MAG)/sulfoglucuronyl paragloboside (SGPG) IgM antibody was also detected. Immunofluorescence analysis of a sural nerve biopsy specimen revealed binding of IgM and lambda-light chain on myelin sheaths. No amyloid deposition was detected in biopsied tissues except for the hard palate, suggesting that the amyloidosis was of the localized type and had no relation to the pathogenesis of cranial neuropathy. Our observations indicate that the anti-MAG/SGPG IgM antibody may be responsible for this patient's cranial polyneuropathy, which is a rare manifestation in anti-MAG/SGPG-associated neuropathy.

Skin denervation in vasculitic neuropathy.

BACKGROUND: Skin denervation in vasculitic neuropathy has rarely been documented despite frequent manifestations of small-fiber neuropathy including reduced sensitivity and neuropathic pain. Recently, skin biopsy has been established as a new approach to diagnose small-fiber sensory neuropathy. OBJECTIVES: To investigate the pathologic features of cutaneous nerves and to evaluate inflammatory vasculopathy in the skin of patients with vasculitis. DESIGN: Case series. SETTING: National Taiwan University Hospital, Taipei. Patients Six patients with vasculitic neuropathy. INTERVENTIONS: Patients had 3-mm punch biopsy specimens taken from the distal part of the leg (without active vasculitic lesions) and a sural nerve biopsy specimen was taken in addition to detailed neurologic examinations, laboratory investigations, and nerve conduction studies. MAIN OUTCOME MEASURES: Results of nerve conduction studies, epidermal nerve fiber density studies, and immunohistochemistry. RESULTS: All 6 patients had combined large- and small-nerve-fiber involvement on the neurologic examinations. Nerve conduction studies showed a pattern of axonal neuropathy or mononeuropathy multiplex. Epidermal nerve fiber densities were significantly reduced in the skin of all patients, consistent with concomitant small-fiber neuropathies. Perivascular infiltration by T cells and macrophages was demonstrated by immunohistochemistry. All patients experienced neurologic improvement in muscle strength and alleviation of sensory symptoms after immunotherapy with corticosteroids, plasma exchange, or cyclophosphamide. CONCLUSIONS: Small-diameter sensory nerves are affected in vasculitis in addition to the well-known effect of vasculitis on large-diameter nerves. Significant inflammatory vasculopathy is present in the skin despite the absence of clinically active vasculitic lesions.

Paraneoplastic encephalomyelitis/sensory motor peripheral neuropathy - an autopsy case study.

Paraneoplastic neurological anti-Hu syndrome is one of the most frequent remote effects of cancer and usually manifests as encephalomyelitis combined with peripheral neuropathy. Subacute sensory neuronopathy, which results from the inflammatory destruction of sensory neurone cell bodies in the dorsal root ganglia, is thought to be the principal presentation of peripheral neuropathy. In addition to sensory involvement, evidence of motor nerve involvement is frequently found. The mechanisms of motor involvement remain largely unclear and there have been only a limited number of pathological studies. We present an autopsy case study of anti-Hu paraneoplastic encephalomyelitis/sensory-motor neuropathy, which confirms an inflammatory paraneoplastic destruction of sensory neuron cell bodies in the dorsal root ganglia and lower motor neurons in the spinal cord, as a cause of clinically rapidly progressive peripheral sensory-motor neuropathy.

Clinicopathological and virological analyses of familial human T-lymphotropic virus type I--associated polyneuropathy.

Human T-lymphotropic virus type I (HTLV-I) is known to be the causative agent of the chronic myelopathy, HTLV-I--associated myelopathy (HAM), and on rare occasions infection is also associated with the development of polyneuropathy. Here the authors present an HTLV-I--positive family of whom four members developed a chronic demyelinating polyneuropathy without HAM. Four female patients in a family from Hokkaido in Japan developed distal dominant paresthesia and muscle weakness in the second and third decades of their life. Neurological findings at ages ranging from 50 to 65 years included mild painful sensorimotor disturbances with atrophy of the distal parts of the extremities but without pyramidal signs or hyperactive tendon reflexes. Magnetic resonance imaging (MRI) findings of brain and spinal cord were unremarkable. Serum HTLV-I antibody levels were elevated at 1:8192 to 1:32,768, whereas those in cerebrospinal fluid were low at 1:4 to 1:8. Electrophysiological studies revealed polyphasic compound muscle action potentials with denervation potentials on nerve conduction studies and neurogenic patterns by electromyography, which were consistent with signs of chronic motor dominant demyelinating polyneuropathy. Sural nerve biopsy showed decreased myelinated fibers, occurrence of globule formation, myelin ovoid and remyelinated fibers, and an infiltration of CD68-positive macrophages with occasional CD4-positive T cells in the nerve fascicles. The polyneuropathy was responsive to steroid therapy. Analyses of serological human leukocyte antigen (HLA) types indicated that none of the patients possessed a high-risk HLA type known to be associated with adult T-cell leukemia (ATL), whereas they did have high responsive alleles to HTLV-I env similar to that observed in HAM. Nucleotide sequence analysis of the HTLV-I tax region demonstrated the B subgroup in all patients. This study suggests that HTLV-I infection can result in the development of a familial form of polyneuropathy that is associated with distinct HLA class I alleles, which might possibly involve a distinct virus subtype.

Dendritic cells in the cerebrospinal fluid and peripheral nerves in Guillain-Barré syndrome and chronic inflammatory demyelinating polyradiculoneuropathy.

The role of antigen-presenting cells (APC) involved in induction of T and B cell mediated autoaggressive immunity in Guillain-Barre syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is poorly understood. We studied the numbers and phenotype of dendritic cells (DC) in blood and cerebrospinal fluid (CSF) over the course of GBS and CIDP before and after immunomodulatory treatment. Four out of seven GBS patients examined prior to treatment with high-dose intravenous immunoglobulins (IvIg) had elevated numbers of CD123(+) plasmacytoid DC in the CSF, while both GBS and CIDP patients examined prior to treatment had elevated numbers of CD11c(+) myeloid DC in the CSF, as compared to patients with noninflammatory neurological diseases (OND). The percentages of blood DC expressing the cell surface marker CD1a, co-stimulatory molecules CD80 and CD86, adhesion molecule CD54, and chemokine receptors CCR1, CCR2, CCR5, and CXCR4 were not affected in GBS or CIDP. The immunohistochemistry of sural nerve biopsies revealed CD11c(+)CD83(-)CD14(-)CD16(-) immature myeloid DC at low numbers, mostly in the perineurium, without difference between CIDP patients and controls. In contrast, the numbers of CD11c(+)CD14(+)/CD16(+) macrophages were higher within the endoneurium in CIDP patients compared with the controls. The recruitment of DC to CSF in GBS and CIDP may be important in capturing antigens released from inflamed spinal nerve roots into CSF and in transferring these antigens from CSF to local lymph nodes, where naive T and B cells may be activated.

Immunolocalization and activation of transcription factor nuclear factor kappa B in dysimmune neuropathies and familial amyloidotic polyneuropathy.

BACKGROUND: Recently, immunoreactivity of transcription factor nuclear factor kappaB (NF-kappaB) was found in peripheral nerves from patients with Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy (CIDP), and familial amyloidotic polyneuropathy (FAP), suggesting a role in their pathogenesis. OBJECTIVE: To investigate expression and activation of NF-kappaB in nerve biopsy specimens from patients with peripheral neuropathies of different origins. PATIENTS: Nerve biopsies from 17 patients (5 with CIDP, 3 with vasculitis, 4 with Charcot-Marie-Tooth disease, and 5 with FAP) and 3 normal sural nerves were studied by immunocytochemistry and Western blot of nuclear extracts for the activated form of NF-kappaB. Nuclear factor kappaB DNA-binding activity was studied by electrophoretic mobility shift assay. RESULTS: Immunobinding for the activated form p65 of NF-kappaB was found in 2% to 5% of endoneurial vessel walls, in the external myelin of 5% to 10% of fibers, and in a few axons in CIDP specimens. It was also found in 5% to 15% of epineurial and endoneurial vessels in vasculitis specimens and at the level of amyloid deposits in FAP nerves. Nuclear factor kappaB immunoreactivity was not correlated to type of inflammatory cells, but it often corresponded to the deposition of the terminal complement complex C5b9. Western blot analysis of nuclear extracts showed a single band corresponding to 65 kDa in all affected nerves. Nuclear factor kappaB DNA-binding activity was revealed by electrophoretic mobility shift assay in specimens from patients with CIDP, vasculitis, and FAP. CONCLUSION: Our novel findings suggest a crucial role of NF-kappaB in inflammatory neuropathies and FAP.

Expression of matrix metalloproteinases in vasculitic neuropathy.

The aim of this study was to investigate the expression pattern and cellular source of matrix metalloproteinases (MMP) in vasculitic neuropathy. Matrix metalloproteinases are endopeptidases degrading components of extracellular matrix proteins, and they have been implicated in the pathogenesis of inflammatory demyelination. They are induced by cytokines, secreted by inflammatory cells, and enhance T cell migration. Vasculitic neuropathy occurs as a component of systemic vasculitis or as an isolated angiitis of the peripheral nervous system, and T cell-mediated inflammation is detected in its pathogenesis. Nerve biopsy sections of eight patients with nonsystemic vasculitic neuropathy (NSVN) and four with systemic vasculitic neuropathy were examined for the presence of CD4+, CD8+, and CD68+ cells and immunohistochemically for MMP-2 and MMP-9 expression. Nerve biopsies of eight patients with noninflammatory neuropathy were used as a control group. Semiquantitative polymerase chain reaction analysis was performed to detect MMP-2 and MMP-9 mRNA. The predominant cells were CD8+ and CD68+ T cells. Expression of MMP-9, but not MMP-2, was increased in perivascular inflammatory infiltrate in nerve tissues of vasculitic neuropathy patients. This MMP-9 expression correlated positively with immunostaining of CD8+ T cells. No difference was detected between immunostaining patterns of nonsystemic and systemic vasculitic neuropathies with the antibodies used, except in MMP-9 immunostaining, which was found to be enhanced in NSVN group. Polymerase chain reaction analysis revealed elevated mRNA levels of MMP-9 and MMP-2 compared with controls, but this did not reach statistical significance. Our results imply a pathogenic role for MMP-9 secreted from CD8+ cells in vasculitic neuropathy.

Increase of sural nerve T cells in progressive axonal polyneuropathy and monoclonal gammopathy.

The authors investigated whether T cells have a role in the pathogenesis of axonal polyneuropathy and monoclonal gammopathy by comparing the presence of T cells in sural nerves of 23 patients with axonal polyneuropathy and monoclonal gammopathy (12 IgM, 11 IgG), of 15 patients with chronic idiopathic axonal polyneuropathy, and of 10 autopsy cases. Seven patients with an increased T-cell density had a progressive disease course, and four of these patients were treated with prednisone with a good response, suggesting that vasculitis plays a role in the pathogenesis.

GalNAc-GD1a in human peripheral nerve: target sites of anti-ganglioside antibody.

BACKGROUND: The authors previously reported that immunoglobulin G (IgG) antibody to the ganglioside N-acetylgalactosaminyl GD1a (GalNAc-GD1a) is associated with the pure motor variant of Guillain-Barré syndrome (GBS). Elucidation of the localization of GalNAc-GD1a in human peripheral nerve tissue may lead to understanding of the pathogenetic role of anti-GalNAc-GD1a antibody in GBS. METHODS: IgG anti-GalNAc-GD1a-monospecific antibody was purified from anti-GalNAc-GD1a antibody-positive rabbit sera through an affinity column. Anti-neurofilament-200 monoclonal and anti-HNK-1 monoclonal antibodies were used as the markers for axon and myelin. Immunohistochemical study using double fluorescence labeling technique was conducted in human ventral roots (VR), dorsal roots (DR), intramuscular nerves, and sural nerves. Human teased ventral fibers also were studied. RESULTS: Anti-GalNAc-GD1a antibody immunostained an inner part of compact myelin and additionally a periaxonal-axolemma-related portion in the VR, small-diameter DR fibers, and IM nerves. In sural nerves, small fibers were selectively stained. In VR, the staining was localized in the paranodal region. CONCLUSION: Anti-GalNAc-GD1a antibodies in patients' sera may bind to those regions in the VR and IM nerves where GalNAc-GD1a is localized, and may function in the pathogenesis of pure motor type GBS. Further investigation is needed to explain the discrepancy between the immunolocalization of GalNAc-GD1a in sensory nerves and the absence of sensory disturbance in patients with GBS with IgG anti-GalNAc-GD1a antibodies.

[Chronic inflammatory demyelinating polyneuropathy]. / Chronisch inflammatorische demyelinisierende Polyneuropathie.

Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired immune-mediated disease of the peripheral nervous system with a prevalence of 1-2/100,000. Clinical and experimental findings suggest a role of immune pathomechanisms;however, the target antigens are still unknown. Beside classic CIDP with symmetrical proximal and distal paresis, subgroups of CIDP with pure motor or sensory deficits have been described. Diagnostic criteria include evidence of demyelination in electrophysiological examination and biopsy as well as elevated protein content in the CSF. Magnetic resonance imaging of plexuses and roots extends the diagnostic armamentarium and may be helpful in differential diagnosis. The utility of immunosuppressant/immunomodulatory therapies has been demonstrated in several studies.

[Structural characteristics of sural nerve myelin from patients with chronic inflammatory demyelinating polyneuropathy: an X-ray diffraction study]. / Características estructurales de la mielina de nervios surales de pacientes con polineuropatía desmielinizante inflamatoria crónica: estudio por difracción de rayos X.

INTRODUCTION AND OBJECTIVE: Using the X ray diffraction technique and the mathematical analysis developed by Luzzati and Mateu, we have studied the structure of nerve myelin from patients with chronic inflammatory demyelinating polyneuropathy (CIDP) in order to quantitatively evaluate the changes occurred in the myelin sheath at structural level. PATIENTS AND METHODS: Sural nerves from 4 patients filling the criteria for CIDP were studied and the results compared to those of 4 other sural nerves extracted from patients who died in the Hospital with no symptoms of peripheral nerve diseases. The structural parameters determined by the mathematical analysis were: the repeat distance between the myelin membranes pairs (D) and its mean standard deviation (sigmaD); the mean number of membrane turns per axon ; the fraction of total myelination (alpha myel) in the nerve, the fraction of membrane pairs not packed in a crystallite (alpha loose) and the degree of disorientation (sigmaw) of the myelin membrane pairs with respect to the fiber axis. RESULTS: The alterations found in pathological nerve myelin were: 1) increase in the packing disorder sigmaD and in the fraction of disordered myelin alpha loose; 2) decrease in the percentage of myelination alpha myel and in the mean number of membrane turns around the axons . CONCLUSIONS: Our results indicate that with these techniques it is possible to detect and quantify demyelination produced by CIDP in human peripheral nerves. In consequence it should be possible to use a similar approach to study other types of polyneuropathy.