Immunohistochemical findings in vasculitic neuropathies

Natural Killer Cells in Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis - A Review of the Literature

Anti-neutrophil cytoplasmic antibody (ANCA)- associated vasculitis (AAV) is a group of systemic autoimmune diseases characterized by inflammation of small- and medium-sized vessels. The three main types of AAV are granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and eosinophilic granulomatosis with polyangiitis (EGPA). A growing number of studies focus on natural killer (NK) cells in AAV. NK cells are innate lymphoid cells with important roles in anti-viral and anti-tumor defense, but their roles in the pathogenesis of autoimmunity is less well established. In this review, we will present a summary of what is known about the number, phenotype and function of NK cells in patients with AAV. We review the literature on NK cells in the circulation of AAV patients, studies on tissue resident NK cells and how the treatment affects NK cells.

Biology of the human blood-nerve barrier in health and disease

A highly regulated endoneurial microenvironment is required for normal axonal function in peripheral nerves and nerve roots, which structurally consist of an outer collagenous epineurium, inner perineurium consisting of multiple concentric layers of specialized epithelioid myofibroblasts that surround the innermost endoneurium, which consists of myelinated and unmyelinated axons embedded in a looser mesh of collagen fibers. Endoneurial homeostasis is achieved by tight junction-forming endoneurial microvessels that control ion, solute, water, nutrient, macromolecule and leukocyte influx and efflux between the bloodstream and endoneurium, and the innermost layers of the perineurium that control interstitial fluid component flux between the freely permeable epineurium and endoneurium. Strictly speaking, endoneurial microvascular endothelium should be considered the blood-nerve barrier (BNB) due to direct communication with circulating blood. The mammalian BNB is considered the second most restrictive vascular system after the blood-brain barrier (BBB) based on classic in situ permeability studies. Structural alterations in endoneurial microvessels or interactions with hematogenous leukocytes have been described in several human peripheral neuropathies; however major advances in BNB biology in health and disease have been limited over the past 50 years. Guided by transcriptome and proteome studies of normal and pathologic human peripheral nerves, purified primary and immortalized human endoneurial endothelial cells that form the BNB and leukocytes from patients with well-characterized peripheral neuropathies, validated by in situ or ex vivo protein expression studies, data are emerging on the molecular and functional characteristics of the human BNB in health and in specific peripheral neuropathies, as well as chronic neuropathic pain. These early advancements have the potential to not only increase our understanding of how the BNB works and adapts or fails to adapt to varying insult, but provide insights relevant to pathogenic leukocyte trafficking, with translational potential and specific therapeutic application for chronic peripheral neuropathies and neuropathic pain.

Vasculitic Neuropathy: A Retrospective Analysis of Nerve Biopsies and Clinical Features from a Single Tertiary Care Center

Objective

Vasculitic neuropathy can be either restricted to the peripheral nerves or associated with systemic involvement of other organs. The objective of this study was to analyze the nerve biopsies reported as "vasculitic neuropathy" with clinical features.

Materials and Methods

All cases diagnosed with vasculitic neuropathy were retrospectively analyzed and categorized as systemic vasculitis and nonsystemic vasculitic neuropathy based on the clinical features. The histological features were further evaluated and classified according to the Peripheral Nerve Society Guidelines.

Results

Of the 126 cases, there were 65 nonsystemic vasculitis, 45 secondary systemic vasculitis, and 16 primary systemic vasculitis. Definite vasculitis was more common in the systemic vasculitis group. The epineurial vessels were predominantly involved with chronic axonal changes.

Conclusion

The sensitivity of definite vasculitis on nerve biopsy was 54.76%. The sensitivity increases when the diagnostic criteria of definite and probable vasculitis were applied taking into account perivascular inflammation accompanied by vascular changes and axonopathy.

The Role of Pericytes in Amyotrophic Lateral Sclerosis

In amyotrophic lateral sclerosis (ALS), motor neurons die selectively. Therefore, initial symptoms that include fasciculation, spasticity, muscle atrophy, and weakness emerge following axons retraction and consequent muscles' denervation. Patients lose the ability to talk and swallow and rely on parenteral nutrition and assisted ventilation to survive. The degeneration caused by ALS is progressive and irreversible. In addition to the autonomous mechanism of neuronal cell death, non-autonomous mechanisms have been proved to be toxic for motor neurons, such as the activation of astrocytes and microglia. Among the cells being studied to unveil these toxic mechanisms are pericytes, cells that help keep the integrity of the blood-brain barrier and blood-spinal cord barrier. In this chapter, we aim to discuss the role of pericytes in ALS.

Inflammatory neuropathies: pathology, molecular markers and targets for specific therapeutic intervention

Inflammatory neuropathies encompass groups of heterogeneous disorders characterized by pathogenic immune-mediated hematogenous leukocyte infiltration of peripheral nerves, nerve roots or both, with resultant demyelination or axonal degeneration or both. Inflammatory neuropathies may be divided into three major disease categories: Guillain-Barré syndrome (particularly the acute inflammatory demyelinating polyradiculoneuropathy variant), chronic inflammatory demyelinating polyradiculoneuropathy and nonsystemic vasculitic neuropathy (or peripheral nerve vasculitis). Despite major advances in molecular biology, pathology and genetics, the pathogenesis of these disorders remains elusive. There is insufficient knowledge on the mechanisms of hematogenous leukocyte trafficking into the peripheral nervous system to guide the development of specific molecular therapies for immune-mediated inflammatory neuropathies compared to disorders such as psoriasis, inflammatory bowel disease, rheumatoid arthritis or multiple sclerosis. The recent isolation and characterization of human endoneurial endothelial cells that form the blood-nerve barrier provides an opportunity to elucidate leukocyte-endothelial cell interactions critical to the pathogenesis of inflammatory neuropathies at the interface between the systemic circulation and peripheral nerve endoneurium. This review discusses our current knowledge of the classic pathological features of inflammatory neuropathies, attempts at molecular classification and genetic determinants, the utilization of in vitro and in vivo animal models to determine pathogenic mechanisms at the interface between the systemic circulation and the peripheral nervous system relevant to these disorders and prospects for future potential molecular pathology biomarkers and targets for specific therapeutic intervention.

Differential gene expression in nerve biopsies of inflammatory neuropathies

DNA microarray analysis is a powerful tool for simultaneous analysis and comparison of gene products expressed in normal and diseased tissues. We used this technique to identify differentially expressed genes (DEGs) in nerve biopsy samples of chronic inflammatory demyelinating polyneuropathy (CIDP) and vasculitic neuropathy (VAS) patients. We found novel previously uncharacterized genes of relevance to CIDP or VAS pathogenesis. Of particular interest in CIDP were tachykinin precursor 1, which may be involved in pain mediation, stearoyl-co-enzyme A (CoA) desaturase, which may be a marker for remyelination, HLA-DQB1, CD69, an early T-cell activation gene, MSR1, a macrophage scavenger receptor, and PDZ and LIM domain 5 (PDLIM5), a factor regulating nuclear factor (NF)-kappa B activity. Genes upregulated in VAS included IGLJ3, IGHG3, IGKC, and IGL, which all function in B-cell selection or antigen recognition of B cells. Other upregulated genes included chemokines, such as CXCL9 and CCR2, as well as CPA3, a mast cell carboxypeptidase. Allograft inflammatory factor-1 (AIF-1), a modulator of immune response was upregulated both in CIDP and VAS. Microarray-based analysis of human sural nerve biopsies showed distinct gene expression patterns in CIDP and VAS. DEGs might provide clues to the pathogenesis of the diseases and be potential targets for therapeutics.

[A patient with Churg-Strauss syndrome presenting as Guillain-Barré syndrome]

A 74-year-old man presented in a pulmonary clinic with symmetrically ascending tetraparesis. Physical and neurophysiological examinations suggested Guillain-Barré syndrome. The patient was treated with an initial course of 7s immunoglobulins without success. His state worsened until he was unable to walk. Severe eosinophilia (41%) was later noted in the differential white blood cell count. Combined with the onset of asthma-like symptoms, this prompted us to suspect Churg-Strauss syndrome. Despite treatment with high-dose corticoids, the palsy did not improve. It was only after immunosuppression with cyclophosphamide that the patient began to recover. The subgroup of necrotising vasculitides must be considered as differential diagnosis of rapidly progressive, symmetrical neuropathy with ascending course. Early identification and treatment are essential, since early immunosuppressive therapy is often successful, whereas delayed initiation of treatment may lead to a fatal outcome.

Cryofibrinogenemia associated with polyarteritis nodosa

We report the case of a 77-year-old woman with biopsy-confirmed polyarteritis nodosa (PAN) associated with cryofibrinogenemia presenting with polyarthralgia and digital gangrene induced by cold exposure. The clinical manifestations and parameters measured by laboratory markers including cryofibrinogen responded well to corticosteroid therapy. To our knowledge, the case of the combination of PAN and cryofibrinogenemia has not been reported. Our case indicates that cryofibrinogenemia might be associated with PAN. The PAN patients with cold-induced symptoms should be screened for cryofibrinogen.

Non-systemic vasculitic neuropathy

PURPOSE OF REVIEW

This article reviews the literature on non-systemic vasculitic neuropathy, with emphasis on recent advances, summarizing the clinical presentation, diagnosis, pathology, treatment, and outcome of this condition, and speculating on its nosological status vis-à-vis the systemic vasculitides.

RECENT FINDINGS

A new cohort of non-systemic vasculitic neuropathy patients was recently reported. Analysis of the clinical characteristics of this cohort demonstrated a higher incidence of painful, asymmetric, overlapping deficits than in previous studies. Extended follow-up revealed a high relapse rate, low risk of systemic spread, high incidence of chronic pain, relatively good neurological outcome, and low mortality rate. Analysis of therapeutic responses showed better outcomes with combination therapy than corticosteroid monotherapy. Another recent report proposed a role for magnetic resonance angiography in the diagnosis and follow-up of non-systemic vasculitic neuropathy. Recent pathological studies implicated proinflammatory cytokines and matrix metalloproteinase-9 in the mediation of vascular and axonal damage in non-systemic vasculitic neuropathy.

SUMMARY

Non-systemic vasculitic neuropathy is one of many localized vasculitides, with involvement restricted to nerves and (possibly) muscles. Inclusion and exclusion criteria differ between reported cohorts. All require a nerve biopsy diagnostic of or suspicious for vasculitis and no extra-neuromuscular involvement. Patients typically present subacutely with a painful, multifocal/asymmetric, distal-predominant neuropathy. In the absence of clinical or laboratory evidence of systemic vasculitis or a condition predisposing to such, prognosis with treatment is good. Pathological data are supportive of a primary T-cell-mediated immunopathogenesis. Some patients classified as having non-systemic vasculitic neuropathy have a systemic vasculitis presenting with neuropathy; in others, the disease is organ-specific.

Receptor for advanced glycation endproduct (RAGE)-mediated nuclear factor-κB activation in vasculitic neuropathy

Binding of ligands to the receptor for advanced glycation endproducts (RAGE) results in activation of the proinflammatory transcription factor nuclear factor-kappaB (NF-kappaB) and subsequent expression of NF-kappaB-regulated cytokines. In order to determine whether engagement of RAGE contributes to the pathogenesis of vasculitic neuropathy, we studied the presence of the RAGE ligand N(epsilon)-(carboxymethyl)lysine (CML), the receptor itself, NF-kappaB, and interleukin-6 (IL-6) in sural nerve biopsies of 12 patients with vasculitic neuropathies and 12 controls. In the patients, CML, RAGE, NF-kappaB, and IL-6 were localized in mononuclear cells, epineurial and endoneurial vessels and the perineurium. CML, RAGE, NF-kappaB, and IL-6 were expressed by CD4(+), CD8(+), and CD68(+) cells invading the nerves. Controls showed only weak staining. These data suggest that the RAGE pathway plays a critical proinflammatory role in vasculitic neuropathy.

Advances in understanding and treatment of immune-mediated disorders of the peripheral nervous system

During recent years, novel insights in basic immunology and advances in biotechnology have contributed to an increased understanding of the pathogenetic mechanisms of immune-mediated disorders of the peripheral nervous system. This increased knowledge has an impact on the management of patients with this class of disorders. Current advances are outlined and their implication for therapeutic approaches addressed. As a prototypic immune-mediated neuropathy, special emphasis is placed on the pathogenesis and treatment of the Guillain-Barré syndrome and its variants. Moreover, neuropathies of the chronic inflammatory demyelinating, multifocal motor, and nonsystemic vasculitic types are discussed. This review summarizes recent progress with currently available therapies and--on the basis of present immunopathogenetic concepts--outlines future treatment strategies.

A case of inflammatory demyelinating polyradiculoneuropathy associated with T-cell lymphoma

Malignant lymphoma may present prominent peripheral nervous system disorders with variable etiologies. We describe a patient who presented with chronic relapsing polyradiculoneuropathy accompanied by right facial nerve palsy. Gadolinium enhancement of the right facial nerve and cervical spinal roots was noted on magnetic resonance imaging (MRI). Sural nerve biopsy specimens showed mononuclear cell infiltration around the vessels in the epineurium. Histopathological and immunohistochemical investigations of sural nerve specimens revealed perivascular infiltration of lymphocytes with T-cell dominancy. No apparent direct invasion of lymphoma cells was seen. The results of nerve conduction studies, sural nerve biopsy and cerebrospinal fluid examination were suggestive of immune-mediated inflammatory demyelinating neuropathy. The chronic and relapsing fashion and unique radiological findings in our patient expand on the previously reported features of peripheral neuropathy associated with peripheral T-cell lymphoma.

Clinicopathological studies of peripheral neuropathy in Churg-Strauss syndrome

Clinicopathological studies were performed on the visceral organs and the sural nerve of a male patient with Churg-Strauss syndrome (CSS) in order to understand the mechanisms of peripheral nervous system damage. A 67-year-old man, with a 2-year history of bronchial asthma, developed acutely painful paraplegia and dyspnea. Laboratory data showed a leukocytosis, an elevated serum creatinine kinase (CK) and marked eosionophilia. Autoantibodies including p- and c-ANCA were negative. Electrophysiological studies revealed a severe sensory-motor neuropathy of multiple mononeuritis type. Steroid pulse therapy performed a day after biopsy of skin, muscle and sural nerve was effective in resolving his respiratory and neurological dysfunction but a perforation of an intestinal ulcer occurred which required surgical intervention. In the biopsied sural nerve and the surgically resected intestine and mesentery there was vasculitis with fibrinoid necrosis accompanied by numerous eosinophils and macrophages containing eosinophil cationic protein (ECP). These findings suggest that in addition to ischemic changes due to vasculitis some neurotoxic substances generated by the eosinophils may be involved in the development of neuropathy in CSS.

Beyond neurons: evidence that immune and glial cells contribute to pathological pain states

Chronic pain can occur after peripheral nerve injury, infection, or inflammation. Under such neuropathic pain conditions, sensory processing in the affected body region becomes grossly abnormal. Despite decades of research, currently available drugs largely fail to control such pain. This review explores the possibility that the reason for this failure lies in the fact that such drugs were designed to target neurons rather than immune or glial cells. It describes how immune cells are a natural and inextricable part of skin, peripheral nerves, dorsal root ganglia, and spinal cord. It then examines how immune and glial activation may participate in the etiology and symptomatology of diverse pathological pain states in both humans and laboratory animals. Of the variety of substances released by activated immune and glial cells, proinflammatory cytokines (tumor necrosis factor, interleukin-1, interleukin-6) appear to be of special importance in the creation of peripheral nerve and neuronal hyperexcitability. Although this review focuses on immune modulation of pain, the implications are pervasive. Indeed, all nerves and neurons regardless of modality or function are likely affected by immune and glial activation in the ways described for pain.

Polyarteritis nodosa and microscopic polyangiitis: etiologic and diagnostic considerations

Polyarteritis nodosa (PAN) is a systemic necrotizing vasculitis of medium-sized vessels with clinical manifestations resulting from ischemia and infarction of affected tissues and organs. Although the cause of most cases of PAN and the related disorder microscopic polyangiitis (MPA) remains largely unknown, there has been significant progress in understanding the pathogenesis of vascular inflammation. The diagnostic approach to PAN and MPA should be individualized and based on specific organ involvement. Because no test or clinical finding reliably indicates the presence or absence of PAN or MPA, diagnosis requires integration of clinical findings, angiography, and biopsy data.

Neuromuscular complications of connective tissue diseases

The connective tissue diseases, such as rheumatoid arthritis, Sjögren's syndrome, systemic lupus erythematosus, systemic sclerosis, and vasculitis, may cause various disorders of the peripheral nervous system. In this review, the clinical effects of the connective tissues diseases on nerve and muscle are examined with particular attention to mononeuritis multiplex, distal symmetric neuropathy, fulminant motor neuropathy, compression neuropathy, sensory neuronopathy, and trigeminal sensory neuropathy.

Cell death in vasculitic neuropathy

Vasculitic neuropathy shows cluster of differentiation (CD)4+ and CD8+ perivascular infiltrates. CD8+ cells kill the target by different ways. Some mechanisms require the release of granzymes and T-cell restricted intracellular antigen (TIA-1) which induce cell death by apoptosis. A nonsecretory ligand-mediated mechanism has been proposed for apoptosis and requires the interaction of Fas and Fas-ligand. We studied apoptosis by immunohistochemistry and terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) in nerve biopsy specimens in 19 cases of vasculitic neuropathy and 8 controls. In vasculitic neuropathy, perivascular mononuclear cells expressed TIA-1, granzyme A, and granzyme B. Regarding the ligand-mediated mechanism, we observed Fas+ and Fas-ligand+ mononuclear cells in an epineurial-perivascular distribution. Cells undergoing apoptosis, as demonstrated by TUNEL, represented mononuclear cells. In vasculitic neuropathy, apoptosis by both a secretory and a nonsecretory mechanism is suspected. However, apoptosis seems to be restricted to inflammatory mononuclear cells, suggesting that it may play a critical role in recovery from vasculitic neuropathy.

Severe polyneuropathy in a patient with Churg-Strauss syndrome

We describe the clinicopathologic features of a 56-year-old woman affected with Churg-Strauss syndrome with major peripheral nerve involvement. The patient presented with a 1-month history of mainly distal upper-limb symmetrical paresthesias and hypostenia (bilateral "wrist drop"), palpable purpura and eosinophilia. Multiple pulmonary infiltrates and asthma had been present since the age of 52. Skin biopsy demonstrated an eosinophilic necrotizing vasculitis. During the hospitalization she was submitted to cardiac, bronchopulmonary, renal, and gastrointestinal evaluation and EMG. Peripheral nerve and skeletal muscle biopsies were performed. Sural nerve biopsy showed a marked degree of demyelination. A perivascular cellular infiltrate within the epineurium was immunoreactive for T lymphocytes and macrophages. Strong HLA-DR immunostaining was present in the endoneurium. IgM, IgE and fibrinogen deposition was found in some epi- and endoneurial vessels. Muscle biopsy showed neurogenic changes and 1 thrombosed vessel surrounded by mononuclear cells. Membrane attack complex (MAC) deposition was present in a few capillaries and major histocompatibility complex products I (MHCP I) was expressed at the subsarcolemmal level in a few isolated perivascular muscle fibers. After immunosuppressive therapy, the patient showed progressive improvement of both clinical symptoms and neurophysiological parameters.

The diagnostic value of sural nerve T cells in chronic inflammatory demyelinating polyneuropathy

BACKGROUND

T-cell infiltrates in sural nerve biopsy specimens of patients with inflammatory neuropathies have been reported, suggesting a role for T cells in the pathogenesis, but the specificity of the presence and localization of sural nerve T cells in chronic inflammatory demyelinating polyneuropathy (CIDP) is unknown.

OBJECTIVE

To study the diagnostic value of the number and distribution of sural nerve T cells in CIDP.

METHODS

We performed a quantitative immunohistochemical examination of T cells in sural nerve biopsy specimens taken from 23 patients with a CIDP and compared them with sural nerves of 15 patients with a chronic idiopathic axonal polyneuropathy (CIAP), 5 patients with a vasculitic neuropathy, and 10 normal controls.

RESULTS

T cells were found in sural nerves of all CIDP patients as well as in all disease and normal controls. Only six CIDP patients had increased numbers and densities of T cells compared with CIAP patients and controls. Based on the distribution of endoneurial or epineurial T cells, it was not possible to differentiate CIDP patients from CIAP patients or normal controls. In patients and controls perivascular epineurial T cells predominated. Increased numbers and densities of sural nerve T cells in patients with CIDP were associated with female sex, a more severe disease course, worse outcome, highly elevated CSF protein level, and a larger sural nerve area, but not with loss of myelinated nerve fibers in the sural nerve biopsy sample or demyelinating features on electrophysiologic examination.

CONCLUSIONS

In the majority of CIDP patients, the number and distribution of T cells in sural nerve biopsy samples were similar to patients with noninflammatory neuropathies and normal controls. Only large numbers of sural nerve T cells are specific for inflammatory neuropathies and therefore of diagnostic value for CIDP.

Clinicopathological features of Churg-Strauss syndrome-associated neuropathy

We assessed the clinicopathological features of 28 patients with peripheral neuropathy associated with Churg-Strauss syndrome. Initial symptoms attributable to neuropathy were acute painful dysaesthesiae and oedema in the dysaesthetic portion of the distal limbs. Sensory and motor involvement mostly showed a pattern of mononeuritis multiplex in the initial phase, progressing into asymmetrical polyneuropathy, restricted to the limbs. Parallel loss of myelinated and unmyelinated fibres due to axonal degeneration was evident as decreased or absent amplitudes of sensory nerve action potentials and compound muscle action potentials, indicating acute massive axonal loss. Epineurial necrotizing vasculitis was seen in 54% of cases; infiltrates consisted mainly of CD8-positive suppressor/cytotoxic and CD4-positive helper T lymphocytes. Eosinophils were present in infiltrates, but in smaller numbers than lymphocytes. CD20-positive B lymphocytes were seen only occasionally. Deposits of IgG, C3d, IgE and major basic protein were scarce. The mean follow-up period was 4.2 years, with a range of 8 months to 10 years. Fatal outcome was seen only in a single patient, indicating a good survival rate. The patients who responded well to the initial corticosteroid therapy within 4 weeks regained self-controlled functional status in longterm follow-up (modified Rankin score was < or = 2), while those not responding well to the initial corticosteroid therapy led a dependent existence (P < 0.01). In addition the patients with poor functional outcomes had significantly more systemic organ damage caused by vasculitis (P < 0.05). Necrotizing vasculitis mediated by cytotoxic T cells, leading to ischaemic changes, appears to be a major cause of Churg-Strauss syndrome-associated neuropathy. The initial clinical course and the extent of systemic vasculitic lesions may influence the long-term functional prognosis.

Vasculitis and the nervous system. Historical perspective and overview

This article is an introduction to the historical background, clinical and laboratory diagnosis, pathogenesis, and treatment of vasculitis involving the peripheral and central nervous system. It also provides a background for the articles that follow.

Detection of Borrelia burgdorferi DNA and complement membrane attack complex deposits in the sural nerve of a patient with chronic polyneuropathy and tertiary Lyme disease

We report a patient who developed a chronic sensory-motor polyneuropathy and a progressive myelopathy 4 years after a tick bite. An increased serum antibody titer to Borrelia burgdorferi suggested a diagnosis of Lyme neuroborreliosis, although a concomitant cervical spondylosis probably contributed to spinal cord damage. Treatment with ceftriaxone resulted in a marked improvement of neuropathic symptoms, providing indirect evidence of spirochetal infection. Search for B. burgdorferi DNA by polymerase chain reaction amplification on sural nerve confirmed the diagnosis, demonstrating that the spirochete localized in the peripheral nervous system. The presence of complement membrane attack complex deposits and macrophage infiltrates around epineurial vessels and within the endoneurium suggests that the neuropathy in our patient was immune-mediated.

Immunohistochemical characterization of inflammatory cells and immunologic activation markers in muscle and nerve biopsy specimens from patients with systemic polyarteritis nodosa

OBJECTIVE

To investigate the phenotype of infiltrating cells in classic lesions of polyarteritis nodosa (PAN).

METHODS

Twenty-one muscle and 10 sural nerve biopsy samples from 24 patients with systemic PAN were studied using avidin-biotin-peroxidase and alkaline phosphatase-anti-alkaline phosphatase immunohistochemical techniques.

RESULTS

The inflammatory infiltrates consisted mainly of macrophages (41%) and T lymphocytes (41%), particularly of the CD4+ subset. Granulocytes were present in varying quantities (0-45%) and were more abundant in heavily infiltrated vessels and in those with fibrinoid necrosis. Dendritic cells could be identified in 4 samples. Proliferating and interleukin-2 receptor-expressing cells, present in 71% and 79% of the patients, respectively, were more frequent in untreated patients.

CONCLUSION

T cell-mediated immune mechanisms may play a role in the development and perpetuation of PAN lesions.