Role of BP230 autoantibodies in bullous pemphigoid

Bullous pemphigoid (BP) is an autoimmune disease associated with subepidermal blistering due to autoantibodies directed against BP180 and BP230. BP180 is currently considered as the major pathogenic autoantigen. However, previous clinical findings suggested that anti-BP230 autoantibodies alone can cause skin lesions in animal models and many BP patients. The characteristics of BP230 and the pathogenic roles of anti-BP230 antibodies have been proposed. First, at the molecular level, BP230 mediates the attachment of keratin intermediate filaments to the hemidesmosomal plaque and interacts with other constituents of hemidesmosomes. Second, the presence of BP230 autoantibodies may correlate with specific clinical features of BP. The immunoglobulin (Ig)G autoantibodies from BP patients react mainly against the C-terminus of BP230, while the IgE autoantibodies are still inconclusive. Third, in vivo, autoantibodies against BP230 involved in the disease may not only induce the inflammatory response but also impair the structural stability of hemidesmosomes. This article reviews recently published work about the role of BP230 and its antibodies, including IgG and IgE, aiming to find clues of its clinical association and lay the foundation for the research on the pathogenicity of antibodies against BP230.

Biological significance of dermal Merkel cells in development of cutaneous nerves in human fetal skin

We detected epidermal Merkel cells in 12-week fetuses with monoclonal antibodies (MAb) against simple epithelium keratin and epithelial membrane antigen. In 15-week fetuses these Merkel cells began to descend into the dermis and expressed nerve growth factor receptors (NGF-R). At approximately the same time, cutaneous nerves, as detected with an MAb against neurofilaments, extended from the subcutaneous trunk and branched to form the subepidermal nerve plexus. The expression of NGF-R on dermal Merkel cells preceded their connection with immunoreactive small nerves. Initially, most of these fine nerve endings were directed towards dermal Merkel cells. In 23-week fetuses the subepidermal nerve plexus was well developed and immunoreactive dermal Merkel cells began to disappear. At all stage of fetal development the epidermal Merkel cells did not strongly express NGF-R. We postulate that dermal Merkel cells play an inductive and a promotional role in development of the cutaneous nerve plexus in the upper dermis.

Dual roles of intermediate filaments in apoptosis

New roles have emerged recently for intermediate filaments (IFs), namely in modulating cell adhesion and growth, and providing resistance to various forms of stress and to apoptosis. In this context, we first summarize findings on the IF association with the cell response to mechanical stress and growth stimulation, in light of growth-related signaling events that are relevant to death-receptor engagement. We then address the molecular mechanisms by which IFs can provide cell resistance to apoptosis initiated by death-receptor stimulation and to necrosis triggered by excessive oxidative stress. In the same way, we examine IF involvement, along with cytolinker participation, in sequential caspase-mediated protein cleavages that are part of the overall cell death execution, particularly those that generate new functional IF protein fragments and uncover neoantigen markers. Finally, we report on the usefulness of these markers as diagnostic tools for disease-related aspects of apoptosis in humans. Clearly, the data accumulated in recent years provide new and significant insights into the multiple functions of IFs, particularly their dual roles in cell response to apoptotic insults.

Regulatory mechanisms and functions of intermediate filaments: a study using site- and phosphorylation state-specific antibodies

Intermediate filaments (IF) form the structural framework of the cytoskeleton. Although histopathological detection of IF proteins is utilized for examining cancer specimens as reliable markers, the molecular mechanisms by which IF are involved in the biology of cancer cells are still unclear. We found that site-specific phosphorylation of IF proteins induces the disassembly of filament structures. To further dissect the in vivo spatiotemporal dynamics of IF phosphorylation, we developed site- and phosphorylation state-specific antibodies. Using these antibodies, we detected kinase activities that specifically phosphorylate type III IF, including vimentin, glial fibrillary acidic protein and desmin, during mitosis. Cdk1 phosphorylates vimentin-Ser55 from prometaphase to metaphase, leading to the recruitment of Polo-like kinase 1 (Plk1) to vimentin. Upon binding to Phospho-Ser55 of vimentin, Plk1 is activated, and then phosphorylates vimentin-Ser82. During cytokinesis, Rho-kinase and Aurora-B specifically phosphorylate IF at the cleavage furrow. IF phosphorylation by Cdk1, Plk1, Rho-kinase and Aurora-B plays an important role in the local IF breakdown, and is essential for the efficient segregation of IF networks into daughter cells. As another part of our research on IF, we have set out to find the binding partners with simple epithelial keratin 8/18. We identified tumor necrosis factor receptor type 1-associated death domain protein (TRADD) as a keratin 18-binding protein. Together with data from other laboratories, it is proposed that simple epithelial keratins may play a role in modulating the response to some apoptotic signals. Elucidation of the precise molecular functions of IF is expected to improve our understanding of tumor development, invasion and metastasis.

Matrix cells from Wharton's jelly form neurons and glia

We have identified an easily attainable source of primitive, potentially multipotent stem cells from Wharton's jelly, the matrix of umbilical cord. Wharton's jelly cells have been propagated in culture for more than 80 population doublings. Several markers for stem cells, including c-kit (CD117), and telomerase activity are expressed in these cells. Treatment with basic fibroblast growth factor overnight and low-serum media plus butylated hydroxyanisole and dimethylsulfoxide induced Wharton's jelly cells to express a neural phenotype. Within several hours of this treatment, Wharton's jelly cells developed rounded cell bodies with multiple neurite-like extensions, similar to the morphology of neural stem cells. Neuron-specific enolase (NSE), a neural stem cell marker, was expressed in these cells, as shown by immunocytochemistry. Immunoblot analysis showed similar levels of NSE expression in both untreated and induced Wharton's jelly cells. After 3 days, the induced Wharton's jelly cells resembled bipolar or multipolar neurons, with processes that formed networks reminiscent of primary cultures of neurons. The neuron-like cells in these cultures stained positively for several neuronal proteins, including neuron-specific class III beta-tubulin, neurofilament M, an axonal growth-cone-associated protein, and tyrosine hydroxylase. Immunoblot analysis showed increasing levels of protein markers for mature neurons over time post induction. Markers for oligodendrocytes and astrocytes were also detected in Wharton's jelly cells. These exciting findings show that cells from the matrix of umbilical cord have properties of stem cells and may, thus, be a rich source of primitive cells. This study shows their capacity to differentiate into a neural phenotype in vitro.

Human monoclonal IgMs with anti-Mycoplasma pneumoniae antibody activity

We have previously reported that IgM antibodies to Pep13 P1, the major immunogenic peptide of Mycoplasma pneumoniae (MP) P1 cytoadhesin involved in microorganism cytoadherence, is a part of the natural antibody repertoire expressed early in life. Hence, Pep13P1 belongs to the panel of self and non-self antigens recognized by the primitive B cell repertoire. Considering that antibody activity of human monoclonal IgM associated with lymphoproliferative diseases is representative of the immune repertoire, we analyze, in this study, the antibody reactivity to P1 of twenty human monoclonal IgMs. Interestingly, we show that 25% of them are of anti-Pep13P1 specificity: one is a MIgM with reactivity against intermediate filaments, two are MIgMs with anti-MAG specificity and two IgMs with previously unknown antibody activity. Our results indicate that anti-P1 IgM antibodies are parts of the autoreactive than the heteroreactive B cell repertoire and Pep13P1 may have structural similarities with an unknown self antigen as the corresponding physiologic ligand.

Neurofilament is an autoantigenic determinant in myasthenia gravis

Intratumorous expression of a 153-kd protein (p153), which contains an acetylcholine receptor-like epitope, is the only tumor marker described to date that significantly associates with thymoma in paraneoplastic myasthenia gravis (MG). Here, we report that p153 is identical to the midsize neurofilament, as verified by immunohistochemistry, immunofluorescence, and western blot analysis. Furthermore, the acetylcholine receptor-like epitope of the midsize neurofilament (NF-M) was identified by peptide epitope mapping. We also show, using T-cell proliferation assays, a significantly increased response of intratumorous T cells to a recombinant midsize neurofilament fragment in thymoma patients with MG compared with MG patients with thymic follicular hyperplasia or thymoma patients without MG. The T cells of thymic follicular hyperplasia and thymoma patients without MG seem to be unresponsive to NF-M. In contrast, we found increased T-cell responses to recombinant acetylcholine receptor fragments in MG patients in general compared with non-MG patients. Increased T-cell responses to NF-M in patients with paraneoplastic MG might be the result of an abnormal positive selection of immature T cells within thymomas, caused by the expression of NF-M in neoplastic thymic epithelial cells. Our results offer further evidence that NF-M expression in thymomas is an autoantigenic determinant in MG.

Novel features of intermediate filament dynamics revealed by green fluorescent protein chimeras

In order to study the dynamic behavior of intermediate filament networks in living cells, we have prepared constructs fusing green fluorescent protein to intermediate filament proteins. Vimentin fused to green fluorescent protein labeled the endogenous intermediate filament network. We generated stable SW13 and NIH3T3 cell lines that express an enhanced green fluorescent protein fused to the N-terminus of full-length vimentin. We were able to observe the dynamic behavior of the intermediate filament network in these cells for periods as long as 4 hours (images acquired every 2 minutes). In both cell lines, the vimentin network constantly moves in a wavy manner. In the NIH3T3 cells, we observed extension of individual vimentin filaments at the edge of the cell. This movement is dependent on microtubules, since the addition of nocodazole stopped the extension of the intermediate filaments. Injection of anti-IFA causes the redistribution or ‘collapse’ of intermediate filaments. We injected anti-IFA antibodies into NIH3T3 cells stably expressing green fluorescent protein fused to vimentin and found that individual intermediate filaments move slowly towards the perinuclear area without obvious disassembly. These results demonstrate that individual intermediate filaments are translocated during the collapse, rather than undergoing disassembly-induced redistribution. Injections of tubulin antibodies disrupt the interactions between intermediate filaments and stable microtubules and cause the collapse of the vimentin network showing that these interactions play an important role in keeping the intermediate filament network extended. The nocodazole inhibition of intermediate filament extension and the anti-IFA microinjection experiments are consistent with a model in which intermediate filaments exhibit an extended distribution when tethered to microtubules, but are translocated to the perinuclear area when these connections are severed.

Monoclonal antibody P-31 recognizes a novel intermediate filament-associated protein (p250) in rat podocytes

The visceral glomerular epithelial cells (GECs) or podocytes of the renal glomerulus constitute a highly specialized epithelium. To study the nature of podocytes, we established mouse monoclonal antibodies against GEC. Clone P-31 reacted exclusively with the cytoplasm of GEC by immunofluorescence. Immunoblot analysis with P-31 showed that a single band of 250 kDa was detectable in a glomerular lysate. The 250-kDa polypeptide (p250) was recovered from Triton X-100-insoluble fractions of isolated glomeruli, suggesting that this molecule is associated with the cytoskeleton. Immunogold staining with P-31 demonstrated that the gold particles were located at the intersections of vimentin-type intermediate filaments of podocytes. In developing kidney, this protein first appeared in immature GECs during the S-shaped body stage. In puromycin aminonucleoside nephrosis, p250 was dramatically increased in glomeruli where enhanced desmin expression was observed in GECs. These results indicate that p250 is a novel intermediate filament-associated protein and plays a role in the organization of the intermediate filament network in both normal and diseased conditions.

Lessons from keratin 18 knockout mice: formation of novel keratin filaments, secondary loss of keratin 7 and accumulation of liver-specific keratin 8-positive aggregates

Here, we report on the analysis of keratin 18 null mice. Unlike the ablation of K8, which together with K18 is expressed in embryonic and simple adult epithelia, K18 null mice are viable, fertile, and show a normal lifespan. In young K18 null mice, hepatocytes were completely devoid of keratin filaments. Nevertheless, typical desmosomes were formed and maintained. Old K18 null mice, however, developed a distinctive liver pathology with abnormal hepatocytes containing K8-positive aggregates. These stained positively for ubiquitin and MM120-1 and were identified as Mallory bodies, one hallmark of human alcoholic hepatitis. This is the first demonstration that the ablation of one keratin leads to the accumulation of its single partner. Another striking finding was the absence or drastic down regulation of K7 in several tissues despite its ongoing transcription. Moreover, K18 null mice revealed new insights in the filament-forming capacity of the tail-less K19 in vivo. Due to the unexpected secondary loss of K7, only K8/19 are expressed in the uterine epithelium of K18 null mice. Immunoelectron microscopy of this tissue demonstrated the presence of typical K8/19 IF, thus highlighting in vivo that K19 is a fully competent partner for K8.

Human monoclonal antibodies encoded by the V4-34 gene segment show cold agglutinin activity and variable multireactivity which correlates with the predicted charge of the heavy-chain variable region

We have characterized the reactivities of a panel of V4-34-encoded human IgM monoclonal antibodies (mAb) which bind the erythrocyte Rh D antigen, derived from an immunized individual. These were compared with the specificities of V4-34-encoded autoantibodies with I/i reactivity produced from patients with cold agglutinin disease (CAD), and other V4-34-encoded autoantibodies. The antibodies were evaluated for cold agglutinin activity using haemagglutination tests, immunofluorescence microscopy for reactivity with tissue components, and in solid phase radiobinding assays with purified antigens. We found that (i) cold agglutinin activity was a property of all the V4-34-encoded mAb (ii) the cold agglutinins from CAD patients were generally monospecific for I/i whereas most of the anti-D and the other V4-34-encoded mAb displayed multireactive properties, frequently binding to strongly acidic antigens (iii) computation of the net charge of the heavy-chain V regions showed that the multireactive mAb were generally more positively charged than the monospecific cold agglutinins, which could contribute to their multireactive phenotype. The involvement of charge interactions was further indicated by the effects of pH and ionic strength on the immunofluorescence staining patterns.

Ovarian Sertoli-Leydig cell tumor: a SRY gene-independent pathway of pseudomale gonadal differentiation

Sertoli-Leydig cell tumors (SLCT) are rare sex-cord stromal tumors of the ovary composed of undifferentiated gonadal stromal cells, Leydig cells (LC), and Sertoli cells (SC), with the latter forming structures resembling fetal testicular tubules. The histogenetic basis of morphological male differentiation patterns in females is controversial. Here, we report a SLCT with intermediate differentiation in a 23-year-old woman investigated by light microscopy, immunohistochemistry for intermediate filaments, and sex steroid hormone receptors (SSHR), as well as by polymerase chain reaction (PCR) for the presence of the sex-determining region Y gene (SRY). Our investigation shows that the SCs of SLCT express progesterone and androgen receptors as well as cytokeratins and vimentin. By PCR, SLCT-derived genomic DNA lacked the SRY gene, indicating that the SLCT results from a SRY gene-independent pathway of pseudomale gonadal differentiation. The expression of progesterone receptors (PRs) in the SCs of the SLCT is in contrast to their absence in testicular SCs, but in line with their presence in ovarian granulosa and surface epithelial cells. Thus, our results provide strong evidence for a close histogenetic relationship between the SLCT and the female gonocyte-supporting cell, the granulosa cell (GC).

Altered intermediate filament expression in human neuroblastoma cells transformed by a growth-promoting agent derived from schizophrenic CSF

1. Transformed (TR) cell lines showed faster doubling times and higher cell densities at confluence, as well as altered morphology, changing from flat epitheloid to smaller round or bipolar shapes. Since such morphological changes are suggestive of alterations in intermediate filaments, we have analyzed the expression of both vimentin and neurofilament. 2. Immunohistochemical analysis of vimentin showed a redistribution from a cytoplasmic network to a perinuclear accumulation in TR cell lines. 3. Western blot analysis demonstrated that the vimentin content was decreased 60-90%. The content of the 70-kD neurofilament protein was also decreased in TR cells, but its intracellular distribution was indistinguishable from that in the control cell lines.

Nuclear antigens, as DNA, of DSB389 MAb and some other anti-desmin monoclonal antibodies

The anti-desmin monoclonal antibodies (MAbs) DSB389, AC54, and DSB860 recognize intermediate filaments (IFs) and nuclear antigens that appear granular, locate around chromosomes, and are insoluble following 0.5% Triton X-100 and cetyltrimethylammonium bromide (CTAB) extraction. Nuclear antigens of the MAbs were searched for in an IFs-deficient clone of SW13 cells. Reactive materials specific to DSB389, AC54, and DSB860 MAbs were trapped at the top of the gel of SDS-agarose-PAGE. The reactivity of the materials disappeared after treatment with DNase I. The reactivity, or trapping of this material at the top of the gel, required previous heat treatment of the sample before application to the gel. The MAbs recognized both single-stranded and double-stranded DNA in ELISA. These results indicate that at least the main nuclear antigens of DSB389, DSB860 and AC54 MAbs are DNA.

Hemidesmosomes: roles in adhesion, signaling and human diseases

Our understanding of the role of hemidesmosomes in cell-substratum adhesion has greatly improved both as a result of targeted gene mutation experiments and by means of observations of several blistering disorders of the skin in which the absence or defects of hemidesmosomal proteins have been demonstrated. Functionally important domains within the proteins that constitute hemidesmosomes have recently been identified by transfection and mutagenesis studies. These multiprotein complexes appear not only to mediate cell adhesion, but also to transduce signals from the extracellular matrix to the cell interior that may profoundly modulate cell behavior.

Expression of neurofilaments and of a titin epitope in thymic epithelial tumors. Implications for the pathogenesis of myasthenia gravis

Autoantibodies against both striated muscle proteins, particularly titin, and the acetylcholine receptor are a hallmark of thymoma-associated myasthenia gravis. However, the stimulus for these responses remains enigmatic as whole titin is not detectable in these tumors. This study reports that in thymomas with cortical differentiation many of the neoplastic epithelial cells expressed low and medium molecular weight neurofilaments detected with several antibodies (on selections and blots) and at the RNA level (by reverse transcriptase polymerase chain reaction). Moreover, higher molecular weight forms sharing at least one epitope with titin were detectable slightly less frequently, as were the more strongly phosphorylated epitopes. In stark contrast, in medullary and mixed thymomas, and especially in the normal thymus, immunoreactivity with anti-neurofilament antibodies was rare. This aberrant overexpression of a titin epitope by epithelial cells with antigen-presenting phenotype in an inappropriate cortical microenvironment suggests that they might autosensitize maturing T cells there and so initiate anti-titin autoimmunity in these patients.

Anti-idiotypic antibody to the V3 domain of gp120 binds to vimentin: a possible role of intermediate filaments in the early steps of HIV-1 infection cycle

Although the CD4 molecule is the major cellular receptor for human immunodeficiency virus (HIV), several lines of evidence suggest participation of additional molecules that are engaged after the binding of HIV to the CD4 receptor and that may facilitate viral entry into the target cell. Some of the post-CD4 binding, perfusion events involve the third hypervariable region (V3 loop) of the viral envelope protein gp120. To identify cellular proteins that interact with the V3 loop, we chose as a probe an antiidiotypic monoclonal antibody (MAb), anti-id2, which was prepared against the neutralizing MAb 110.4 that binds the V3 domain in the envelope glycoprotein gp120 of the LAI isolate of HIV-1. Anti-id2 reacted specifically with a 55- to 60-kDa protein in human T cell and monocytoid cell lines, and in a mouse melanoma cell line. This protein was identified immunologically and by protein sequence analysis as vimentin, an intermediate filament protein of lymphoid and other cells of mesodermal origin. Antiserum raised against vimentin inhibited nuclear translocation of HIV-1 DNA following infection of monocytes and CD4+ T cells with live virus, and reduced the amount of HIV-1 gag-specific RNA in the nuclei of monocytes following inoculation with HIV-1 pseudovirions. These data suggest that vimentin may participate in the early steps of HIV-1 replication, perhaps during the uptake of HIV-1 preintegration complexes into the nuclear compartment.

Stable, detyrosinated microtubules function to localize vimentin intermediate filaments in fibroblasts

Separate populations of microtubules (MTs) distinguishable by their level of posttranslationally modified tubulin subunits and by their stability in vivo have been described. In polarized 3T3 cells at the edge of an in vitro wound, we have found a striking preferential coalignment of vimentin intermediate filaments (IFs) with detyrosinated MTs (Glu MTs) rather than with the bulk of the MTs, which were tyrosinated MTs (Tyr MTs). Vimentin IFs were not stabilizing the Glu MTs since collapse of the IF network to a perinuclear location, induced by microinjection of monoclonal anti-IF antibody, had no noticeable effect on the array of Glu MTs. To test whether Glu MTs may affect the organization of IFs we regrew MTs in cells that had been treated with nocodazole to depolymerize all the MTs and to collapse IFs; the reextension of IFs into the lamella lagged behind the rapid regrowth of Tyr MTs, but was correlated with the slower reformation of Glu MTs. Similar realignment of IFs with newly formed Glu MTs was observed in serum-starved cells treated with either serum or taxol to induce the formation of Glu MTs. Next, we microinjected affinity purified antibodies specific for Glu tubulin (polyclonal SG and monoclonal 4B8) and specific for Tyr tubulin (polyclonal W2 and monoclonal YL1/2) into 3T3 cells. Both injected SG and 4B8 antibodies labeled the subset of endogenous Glu MTs; W2 and YL1/2 antibodies labeled virtually all of the cytoplasmic MTs. Injection of SG or 4B8 resulted in the collapse of IFs to a perinuclear region. This collapse was comparable to that observed after complete MT depolymerization by nocodazole. Injection of W2, YL1/2, or nonspecific control IgGs did not result in collapse of the IFs. Taken together, these results show that Glu MTs localize IFs in migrating 3T3 fibroblasts and suggest that detyrosination of tubulin acts as a signal for the recruitment of vimentin IFs to MTs.

Association of a transglutaminase-related antigen with intermediate filaments

A mouse monoclonal antibody, G92.1.2, raised against guinea pig liver transglutaminase (TGase) recognizes an antigen present in primary mouse dermal fibroblasts. A filamentous pattern, bearing remarkable similarity to the vimentin intermediate filament (IF) network, is seen when these cells are fixed and processed for indirect immunofluorescence with the antibody. Double-label immunofluorescence reveals that the antigen reacting with the antibody colocalizes precisely with vimentin IF and that this colocalization is retained after the treatment of fibroblasts with colchicine, which induces a redistribution of the majority of IFs into perinuclear aggregates. These morphological observations are further supported by the finding that the protein reacting with G92.1.2 is retained in IF-enriched cytoskeletal preparations made by using nonionic detergent-containing high ionic strength solutions. Western blots of the IF fraction show that G92.1.2 recognizes a major band of approximately 280 kDa and does not cross react with vimentin. Furthermore, when the antibody is microinjected into live dermal fibroblasts, it causes a collapse of the vimentin IF network in the majority of injected cells. The results suggest that a form of TGase, or a TGase-related antigen, is closely associated with the vimentin IF network of primary cultures of mouse dermal fibroblasts.

The resistant hepatocyte model of carcinogenesis in the rat: the apparent independent development of oval cell proliferation and early nodules

The early cellular changes in the Solt-Farber resistant hepatocyte model of carcinogenesis have been studied to clarify the relationship of oval cell proliferation to the development of early hepatocyte nodules. Cellular proliferation, intermediate filament profiles and the expression of specific cytochrome P450 enzymes were examined. At 24 h after partial hepatectomy (PH) many of the bile ductular cells were in S phase, but over the next few days DNA synthesis progressively decreased in the portal bile ducts and was more common in arborizing ductules (oval cells) radiating from the portal areas. These cells strongly expressed cytokeratins 8 and 19 and vimentin, and from 1 week after PH they frequently underwent differentiation either into hepatocytes, expressing cytochrome P450 enzymes, or into intestinal-type cells. Five days after PH, numerous basophilic foci were discernible, and these expanded rapidly. The ductular cells swirled around the foci, but their antigenic profile clearly indicated that these cells were not involved in the development of these early nodules. In normal hepatocytes, cytokeratin 8 immunoreactivity was distinctly membranous in location, and could only be readily detected in periportal hepatocytes. In the basophilic hepatocyte foci, overexpression of cytokeratin 8 was consistently associated with cells organizing into acini, with expression reminiscent of authentic bile ducts, possibly indicating a structure-function relationship. In conclusion, early foci and nodules in this model are derived from resistant hepatocytes and not ductular oval cells, the latter being a facultative multipotential stem cell compartment.

Linear IgA bullous dermatosis with autoantibodies to a 290 kd antigen of anchoring fibrils

We describe a patient with a papulovesicular eruption associated with scarring and severe mucosal lesions that led to blindness. Direct immunofluorescence showed linear IgA deposits at the dermoepidermal junction. Indirect immunofluorescence microscopy showed that the patient's serum reacted with the dermal side of salt-split skin. Direct immunoelectron microscopy showed the IgA deposits to be associated with anchoring fibrils, whereas with Western blot analysis the patient's serum reacted with a 290 kd dermal antigen. On the basis of these findings, we suggest that our case may represent a form of IgA-mediated epidermolysis bullosa acquisita.

Intermediate filament reactivity in hyperplastic and neoplastic lesions from medaka (Oryzias latipes)

To determine if hyperplastic and neoplastic lesions from medaka showed similar immunoreactivity to intermediate filament antibodies as the tissues of origin, two week old medaka were exposed to 10 or 20 mg/L of methylazoxymethanol acetate for two hours and transferred to clean water for up to six months. Using a streptavidin peroxidase method, paraffin embedded Bouins fixed neoplasms were incubated with cytokeratin, vimentin, or neurofilament antibodies. Like their nonneoplastic cellular counterparts, hepatocellular carcinoma, pancreatic acinar carcinoma and mesenchymal neoplasms including hemangioma and hemangiopericytoma reacted negatively to cytokeratin antibodies. Cholangiocarcinoma, mesothelioma, and proliferative lesions containing biliary epithelial cells reacted positively to cytokeratin antibodies. All neoplasms and proliferative lesions were negative with vimentin and neurofilament antibodies. These data indicate that while some epithelial neoplasms showed cytokeratin reactivity similar to the parent tissues, additional markers are needed to identify mesenchymal tissues and neoplasms.

Brief, high-temperature heat denaturation (pressure cooking): a simple and effective method of antigen retrieval for routinely processed tissues

The merits of microwave-based antigen retrieval methods for diagnostic immunohistochemistry have recently been emphasized. As such technology has drawbacks for busy routine laboratories, we have investigated an alternative method of heat-mediated antigen retrieval (HMAR), using a domestic pressure cooker as a source of superheating. A simple protocol, with superheating in 0.01 M citrate buffer (pH 6.0) for 2 min, gave results comparable to those obtainable in a microwave oven. The range of antigens retrieved and the antigens for which heating was ineffective matched the published microwave experience. The advantages included the speed of treatment, the reproducibility of results with large batches of slides, the ability to use metal slide racks, and economy of time and equipment costs.

Phosphorylated neurofilament epitopes in neuronal perikarya in the septum, mesencephalon and dorsal root ganglia of mammals and birds

We and other researchers have previously described the presence of axon-specific phosphorylated neurofilament epitopes in the cell bodies of three neuronal types in the rat: bipolar septofimbrial neurons and the large light A-type cells in the dorsal root ganglia and the mesencephalic nucleus of the Vth nerve. This spontaneous presence of phosphorylated neurofilaments at the level of the perikaryon contrasts with the induced appearance of these epitopes in axotomized neurons. We have undertaken a study of this phenomenon in rat, mouse, gerbil, rabbit, pig and chicken to analyse its species distribution. Phosphorylated neurofilament positive perikarya could be detected in the dorsal root ganglia and mesencephalic nucleus of the Vth nerve in all analysed species. Although this labelling has been shown to be specific for A-type cells in rat, in pig small cells were preferentially labelled, whereas the largest cells were mostly completely devoid of label. In the septofimbrial nucleus, phosphorylated neurofilament positive perikarya were seen in rat, mouse, gerbil and rabbit. In the pig, only a phosphatase-insensitive neurofilament antibody labelled these neurons. In the chicken, the labelling was completely absent. These observations establish the widespread species distribution of perikaryal phosphorylated neurofilament epitopes in the dorsal root ganglia and mesencephalic nucleus of the Vth nerve. In the septofimbrial nucleus however, this phenomenon seems to be restricted to rodents and lagomorphs. We discuss possible explanations for these cytoskeletal singularities in dorsal root ganglia, the mesencephalic nucleus of the Vth nerve and septofimbrial neurons.

Anticytoskeletal autoantibody development in adjuvant arthritis

OBJECTIVE

Because the presence of autoantibodies against cell components is a common feature of most autoimmune diseases and some of these autoantibodies have been detected in sera of patients with rheumatic diseases such as rheumatoid arthritis (RA), we studied the presence of autoantibodies to cell components in an experimental model of chronic inflammation in rats, adjuvant arthritis (AA), to determine possible similarities between AA and human RA.

METHODS

Sera from arthritic rats were initially tested by indirect immunofluorescence using rat liver sections as a substrate. Afterwards, arthritis sera were further studied in cultures of human skin fibroblasts and the HEp-2 cell line, with or without colchicine treatment.

RESULTS

Results using liver as substrate showed that 31% of the arthritic rats showed a cytoskeleton staining pattern throughout the cytoplasm, with higher intensity of staining along the surface membranes, particularly in pericanalicular regions. This staining was suggestive of intermediate filament autoantibodies. When sera were analyzed on cultured cells, the results showed that the pattern is identical to the arrangement described for intermediate filaments and different from those seen with antiactin antibodies. Colchicine pretreatments ruled out antitubulin activity. Further analysis by immunoblotting revealed that autoantibodies did not recognize intermediate filament proteins when these were denatured in the electrophoretic process.

CONCLUSION

The development of autoantibodies to intermediate filament proteins, both cytokeratin and vimentin, has been demonstrated in sera from rats with AA, in a similar manner to that described in human RA.

Practical applications of some antibodies labelling the human retina

Eight enucleated eyes were promptly fixed in 10% formalin and processed for light microscopy. Employing the ABC technique, we used antibodies against neuron-specific enolase (NSE), synaptophysin (SY), neurofilament (NF), glial fibrillary acidic protein (GFAP), keratins, LEU-7 and S-100 protein. Using NSE we found immunoreactivity in all sensory layers except the outer segments of photoreceptors which were nonreactive. SY showed a striking immunoreactivity of the synaptic regions (outer plexiform and inner plexiform layers). NF labelled the axons of the ganglion cells. GFAP stained perivascular glial cells and Müller cells only in areas of peripheral microcystoid degeneration. Keratin was non-reactive in all layers. LEU-7 showed that all layers were moderately reactive while the Müller cell processes and the outer limiting membrane were strongly immunoreactive. S-100 protein stained the perivascular glial cells in the nerve fiber layer. We conclude that NSE and LEU-7 are helpful markers for most layers of the sensory retina; GFAP and LEU-7 clearly outline Müller cells and GFAP immunoreacts with astrocytes; NF is specific for axons and SY labels vividly the synaptic regions.

Neurofilament expression in human T lymphocytes

The expression of intermediate filaments in normal cells is mainly determined by their embryonal developmental origin. Flow cytometry using monoclonal antibody RT97 demonstrated that neurofilament was detectable in the human HuT 78 T-cell line and on resting T lymphocytes. Expression was greatly increased on lymphocytes activated for 3 days with phorbol ester. Western blotting confirmed the presence of the 200,000 MW form of neurofilament in T lymphocytes. Stimulation of peripheral blood T cells with phorbol myristate acetate (PMA) or with anti-CD3 monoclonal antibodies resulted in a marked increase in detection of phosphorylated neurofilament on Western blotting. Stimulation of HuT 78 cells with anti-LFA-1 resulted in redistribution of neurofilament from a perinuclear spheroid core into dendritic processes. These data indicate that T cells activated through the T-cell receptor associated complex express an intermediate filament usually associated with neurally derived cells. The finding that neurofilament expression and organization are regulated by T-cell surface molecules suggests a role for this intermediate filament in T-cell function.

Neurofilament in feline primary afferent neurones: a quantitative immunocytochemical study

Two populations of cat L4 dorsal root ganglion (DRG) neurones were apparent from their Nissl staining with Toluidine blue. One had neurones of all sizes and the other had predominantly small neurones. The size distribution of neuronal profiles in the two populations overlapped and both were approximately normal. They corresponded to the light (L) and small dark (SD) cell populations previously described in rat DRGs. These neurones were examined with four antibodies to neurofilament: RT97, NFH, 155 and anti-68kD. RT97 is specific for the phosphorylated form of the 200 kDa subunit; NFH recognises both phosphorylated and non-phosphorylated forms of this subunit; 155 and anti-68 kDa recognise the 155 kDa and 68 kDa subunits respectively. The clearest differential labelling was seen with NFH and RT97 and this labelling was compared with cell size. High intensity NFH labelling was in a population of neuronal profiles of all sizes and low intensity labelling in a population of predominantly small neuronal profiles. These populations corresponded respectively to the L and SD populations seen with toluidine blue staining. In the rat, these populations can be demonstrated by both NFH and RT97. In contrast in the cat, high intensity RT97 labelling was seen in only 75% of the L neuronal profiles defined with NFH and was also seen in some SD neuronal profiles defined with NFH. It is thus proposed that L and SD cell types are present in the cat DRG and can be demonstrated using the anti-neurofilament marker, NFH.

Neurofibrillary tangles in the neurons of spinal dorsal root ganglia of patients with progressive supranuclear palsy

Neurofibrillary tangles (NFTs) occur in neurons of human central nervous system (CNS) both in aged subjects and patients with several degenerative diseases, with a certain topographical predilection. In surveying the NFT distribution in nervous tissue of patients with progressive supranuclear palsy (PSP), we found silver-positive fibrillary tangles in the neurons of dorsal root ganglia (DRG) in two of five patients. By immunohistochemistry, these tangles were stained with antibodies to human tau protein, paired helical filaments (PHFs) and ubiquitin. Electron microscopy revealed that they were mainly composed of PHFs that were morphologically indistinguishable from PHFs in the NFTs of CNS typically seen in Alzheimer's disease brains. Our data demonstrate for the first time that the neurons of DRG produce NFTs in PSP and suggest that the pathological process(es) leading to tangle formation can occur in the neurons of the peripheral nervous system in this disease condition.

Defective mononuclear phagocyte function in systemic lupus erythematosus: relationship of FcRII (CD32) with intermediate cytoskeletal filaments

To investigate the mechanisms of impaired Fc receptor-mediated mononuclear phagocyte system (MPS) clearance in systemic lupus erythematosus (SLE), we have examined FcRII (CD32) and vimentin function in 25 patients with SLE and 36 healthy adults. In SLE, FcR-mediated phagocytosis of IgG-sensitized bovine erythrocytes was decreased (5.9 +/- 2.47 vs. 8.3 +/- 3.59 erythrocytes phagocytosed/monocyte/h; p < 0.05), and CD32 and vimentin expression was within the normal range; however, the percentage of simultaneously CD32+ and vimentin+ cells was increased (30 +/- 12 vs. 20 +/- 13; p < 0.05). Circulating immune complexes (CIC) were positive in 11 SLE patients, and levels were positively correlated with proteinuria (r = 0.53; p < 0.05) and disease activity (r = 0.40; p < 0.05). The mobility of membrane molecules, measured as the percentage of patients that showed patching and/or capping of CD32, was increased compared with controls, but not significantly (p < 0.1). At the same time, redistribution of vimentin filaments was observed. In conclusion, our data seem to support the possibility of a functional and/or structural alteration in the relationship between Fc receptors and intermediate cytoskeletal filaments as a causative factor in the deficient internalization of ligands bound to Fc receptors in monocytes of SLE patients.

An antibody against phosphorylated neurofilaments identifies a subset of damaged association axons in Alzheimer's disease

We studied axonal damage in Alzheimer's disease frontal cortex and hippocampus with a novel monoclonal antibody (SMI 312) against phosphorylated neurofilaments. This antibody immunolabeled, with great detail, the neuropil axonal network. In aged normal cases only a few pyramidal cell perikarya were immunostained. In Alzheimer's disease there was a two- to four-fold increase in neuronal SMI 312 immunolabeling, and neuropil neuritic processes were severely disrupted. Double-immunolabeling analysis showed that 88% of SMI 312-immunolabeled abnormal neuritic clusters were associated with amyloid, whereas the remaining 12% were not. Serial section analysis and 3-D reconstructions suggested that dystrophic neurites of classical plaques were derived from long axons. These abnormal neurites were also growth-associated protein 43 positive and occasionally tau positive. The present study supports the contention that a subpopulation of aberrantly sprouting axons in the neuritic plaque is derived from cortico-cortico fibers. This disruption of the neocortical association fibers and neuritic microcircuitry could underlie the cognitive impairment of Alzheimer's disease.

Characterisation of human tumour cell lines using antibodies to intermediate filaments

The human hepatoma cell line G2 (Hep G2) has been compared to lung carcinoma, sarcoma and skin fibroblasts for the expression of intermediate filaments, i.e. vimentin and cytokeratin. The immunofluorescence study revealed that, in contradiction to Szecheng et al. (1987), cytokeratin and vimentin are absent in Hep G2. Human skin fibroblasts and sarcoma cells expressed vimentin as expected for their mesenchymal origin, but a positive reaction to vimentin could also be shown in lung carcinoma cells. However, the vimentin filament structure of both these tumour cell lines was different in comparison with skin fibroblasts. Therefore determining the exact tissue origin of tumour cell lines by means of intermediate filament characterization remains doubtful.

Increased number of immunoreactive nerve fibers in atopic dermatitis

The presence of immunologic markers for neurofilaments, neuropeptides of sensory nerve fibers (Calcitonin gene-related peptide and substance P), for noradrenergic innervation (neuropeptide Y and Tyrosine hydroxylase), and Neuron-specific protein 9.5 was evaluated in frozen tissue sections from normal skin (n = 34) and from skin biopsies manifesting urticaria (n = 6), leukocytoclastic vasculitis (n = 4), systemic lupus erythematosus (n = 23), and atopic dermatitis (n = 40, of which 16 were from lesions induced by epicutaneous atopic allergen patch tests). In some normal skin specimens immunoreactive nerve fibers expressing Neuron-specific protein 9.5 were observed in the epidermis, dermis, and around blood vessels. For the other markers, immunolabeling was mainly observed in the dermis around blood vessels. Neurofilaments, which are scarce in normal skin epidermis, were present in higher density in the epidermis of affected skin in all disease conditions. Biopsies from urticaria and systemic lupus erythematosus showed a decrease in density of fibers immunolabeled for neuropeptides substance P and Calcitonin gene-related peptide and for Neuropeptide Y. In biopsies from skin with atopic dermatitis, an increased density of fibers was observed for all markers except Neuropeptide Y and Tyrosine hydroxylase. In this group, biopsies from positive atopic allergen patch tests showed an enhanced density of fibers labeled by antibody to Neuron-specific protein 9.5 and a lower density in labeling for Tyrosine hydroxylase. The data indicate a potential role of innervation and neuropeptides in dermatoses like atopic dermatitis.

Evaluation of commercially available antibodies to cytokeratin intermediate filaments and laminin in normal cat pinna

The pattern of distribution of cytokeratin (CK) intermediate filaments can be used to characterize subsets of epithelial tissues. The purpose of the study was to examine the CK expression of feline pinna skin. Six normal feline pinnae were routinely processed in formalin. An immunohistochemical method was used to stain the pinnae with 8 commercially available anti-human CK antibodies (Abs) (PKK1, CAM 5.2, UCD 10/11, 35BH11, 34BE12, AE1/AE3, MAK 6, A575) and an anti-human laminin Ab. All the CK Abs selectively localized to epithelium except 35BH11, which did not react with any part of the pinna. Some epithelial subsets were identified by their unique staining pattern with CK Abs. Basal cells but not suprabasal cells of the epidermis stained with PKK1; basal but not lumenal cells of apocrine glands stained with 34BE12. Apocrine glands stained with all CK Abs except 35BH11. All epithelial structures were stained with A575. Basal lamina of epithelial and mesenchymal tissues was clearly identified by the anti-laminin Ab. The results indicate that in cat pinna some commercially available anti-human CK Abs selectively stain subsets of epithelium and adnexa. PKK1, 34BE12, and A575 were the CK Abs with the most consistent staining patterns, the other Abs stained more variably from pinna to pinna. The pattern of epithelial and adnexal staining was similar but not identical to that reported for humans.

Specific monoclonal antibodies against normal microtubule-associated protein-2 (MAP2) epitopes present in Alzheimer pathological structures do not recognize paired helical filaments

We have developed monoclonal antibodies that detect normal microtubule-associated protein-2 (MAP2) epitopes in routinely fixed, paraffin-embedded tissue. The somatodendritic distribution of MAP2 in bovine and human nervous tissue was confirmed with several of these antibodies. Furthermore, some of these antibodies immunohistochemically labeled certain pathological structures in Alzheimer brain, especially neurites in senile plaques. Electron microscopic observations, however, indicate that these MAP2 epitopes are not located in the Alzheimer paired helical filaments themselves, but in amorphous granular structures coexistent with them. While the pathological nature of these structures is undetermined, they may represent artefactual modifications of normal cytoskeletal components.

Detergent-Insoluble Cortical Lewy Body Fibrils Share Epitopes with Neurofilament and ?

Lewy bodies are cytoskeletal inclusions associated with neuronal injury and death in idiopathic Parkinson's disease and other neurodegenerative disorders. The chemical composition of the 8-10-nm fibrils of the Lewy body is unknown, although they are related to both normal cytoskeletal elements and paired helical filaments of Alzheimer neurofibrillary tangles. From the Lewy body-rich cerebral cortex of patients with diffuse Lewy body disease we have isolated intact Lewy bodies using a high salt buffer/nonionic detergent gradient centrifugation procedure and extracted the constitutive fibrils with urea and sodium dodecyl sulfate. Urea/detergent-resistant Lewy body fibrils were solubilized with formic acid and found to contain a single protein band of 68 kDa, which was not found in identically prepared normal brain homogenates. The Lewy body derived-polypeptide was recognized on immunoblots by a polyclonal antibody that reacted with both the 68-kDa neurofilament subunit and the microtubule-associated protein tau. The 68-kDa Lewy body protein was not labeled by the monoclonal antibody tau-1 despite prior in vitro enzymatic dephosphorylation. We conclude that the detergent-insoluble component of the cortical Lewy body fibril shares epitopes with neurofilament and tau and may be a posttranslationally modified derivative of either neurofilament or tau with substantially altered biochemical and immunologic properties.

Autoantibodies to major and minor nuclear lamins are not restricted to autoimmune diseases

Autoantibodies to lamins, the major polypeptide components of the nuclear lamina, have been reported in selected sera from patients with autoimmune diseases, including anti-lamin B in systemic lupus erythematosus (SLE) and anti-lamins AC in autoimmune chronic active hepatitis (CAH). We have studied the frequency, specificity, and isotypy of autoantibodies to major and minor lamins by immunoblotting on purified rat liver lamins in 190 sera from normal controls (n = 62), rheumatic disease controls (n = 42), and autoimmune disease patients (n = 86). The frequency of anti-lamin in normal controls was 85.5%, and ranged from 77 to 100% in the other groups. Anti-lamin frequency was not related to age, sex, or disease duration. Reactivity with lamin A or with minor lamins only was observed with 7 various sera and 2 normal sera, respectively. Between groups, the proportions of reactive sera were not different for lamins AC (18-47%) and for lamin B (22-36%). In particular, anti-lamin B and anti-lamins AC were not more common in SLE or CAH than in normal sera. The most frequent lamin specificity of SLE sera was anti-lamins ABC. Anti-lamin isotypes were IgG and/or IgM. Titers of IgM antibodies were not higher in any group. However, IgG anti-lamin titers were higher in CAH than in normal, ankylosing spondylitis, or SLE sera. The highest end point titers (greater than or equal to 1:3200) were observed with CAH, SLE, and rheumatoid arthritis (RA) sera with IgG anti-lamins AC, B, or ABC, or with IgM anti-lamins ABC. None of these SLE and RA patients had evidence of liver disease. Reactivity with minor lamins was more frequent in CAH. We conclude that anti-lamin autoantibodies are present in sera from most individuals and that the highest titers are found in sera from patients with autoimmune diseases.

Involvement of the consensus sequence motif at coil 2b in the assembly and stability of vimentin filaments

Nearly all intermediate filament (IF) proteins share two sequence motifs located at the N- and the C-terminal ends of their helical rod domain (‘coil 1a’ and ‘coil 2b’, respectively). To examine the structural role of the coil 2b motif, we have performed in vitro assembly studies and in vivo microinjection experiments employing two site-specific reagents: (a) a 20-residue synthetic peptide (C-2) representing the conserved motif itself and (b) a monoclonal antibody (anti-IFA) that recognises an epitope within the conserved coil 2b sequence. We demonstrate here that vimentin protofilaments, when induced to assemble in the presence of C-2 or anti-IFA, show a lower propensity to polymerise and yield various abberant structures. The few filaments that are formed under these conditions appear much shorter than normal IFs and are unravelled or aggregated. Furthermore, when preformed vimentin filaments are exposed to C-2 or anti-IFA, most of the normal IFs are converted into shorter filamentous forms that possess an abberant morphology. None of these effects is seen when vimentin subunits are coincubated with control peptides. Microinjection of anti-IFA into the cytoplasm of interphasic 3T3 cells provokes collapse of vimentin IFs into a juxtanuclear mass and formation of numerous amorphous aggregates distributed throughout the cytoplasm. These two effects are not seen when the anti-IFA is microinjected into the cell nucleus. Our results provide experimental evidence supporting previous suggestions for a role for the conserved coil 2b sequence in filament assembly. We propose that this region is interacting with other sites along the vimentin molecule and that these interactions are essential for proper protofilament-protofilament alignment and filament stability.

Relationships between Lewy bodies and pale bodies in Parkinson's disease

The prevalence of pale bodies and Lewy bodies was studied in the substantia nigra of 12 patients with typical Parkinson's disease (PD), in 5 patients with diffuse Lewy body disease (DLBD), and in a group of neurologically normal controls. Anti-ubiquitin antibodies labelled pale bodies and Lewy bodies in typical PD and DLBD, and there was a strong positive correlation between numbers of ubiquitin-immunoreactive pale bodies and Lewy bodies. BF10, a monoclonal antibody against a phosphate-dependent epitope of neurofilament 155-kDa polypeptide subunit, immunolabelled 57% of Lewy bodies and 15% of pale bodies in typical PD. Some pale bodies and Lewy bodies were seen in the substantia nigra of 2 of 5 neurologically normal, aged controls, probably representing "incidental PD". We conclude that there is a close relationship between pale bodies and typical Lewy bodies in the substantia nigra in clinical varieties of PD, and that these inclusions share antigenic determinants. If pale bodies and Lewy bodies reflect separate aspects of the cellular pathology in PD, their formation probably occurs in parallel. Alternatively, these observations may suggest that pale bodies represent a stage in the formation of Lewy bodies.

Chemoreceptor A-fibres in the human carotid body contain tyrosine hydroxylase and neurofilament immunoreactivity

Previous retrograde tracing studies on rat and guinea-pig showed a projection of sensory tyrosine hydroxylase-immunoreactive neurons to the region of the carotid bifurcation via the carotid sinus nerve. In the present study, focussing on the sensory innervation of the human carotid body, antisera to tyrosine hydroxylase and other catecholamine synthesizing enzymes were applied for an immunohistochemical investigation of carotid bodies obtained at autopsy. In addition, an array of antisera directed to non-enzyme antigens known to be present in viscero-afferent neurons were incorporated in the study. The glomic lobules consisting of glomus cells and sustentacular cells contained a variable number of enzyme-immunoreactive glomus cells. Arteries were supplied by nerve fibres displaying the full phenotype of sympathetic noradrenergic axons, i.e. immunoreactivity to tyrosine hydroxylase, aromatic-L-amino-acid-decarboxylase and dopamine-beta-hydroxylase. The glomic lobules, however, were densely innervated by tyrosine hydroxylase-immunoreactive axons lacking immunoreactivity to aromatic-L-amino-acid-decarboxylase and dopamine-beta-hydroxylase. These fibres reacted with neurofilament 160kD-antibody but were devoid of immunoreactivity to all neuropeptides tested (calcitonin gene-related peptide, somatostatin, substance P). Ultrastructurally, tyrosine hydroxylase/neurofilament 160kD-immunoreactive axons gave rise to large axonal swellings filled with mitochondria and vesicles, and established extensive contacts to glomus cells. Nerve bundles surrounded by a perineural sheath contained both myelinated (2.0-2.8 microns in diameter) and unmyelinated (0.14-3.0 microns) tyrosine hydroxylase-immunoreactive axons. Most of the unmyelinated immunoreactive axons were running singularly within a Schwann cell-sheath. Judged from the pattern of immunoreactivities as well as their preterminal and terminal ultrastructure, tyrosine hydroxylase-immunoreactive axons innervating glomus cells are of sensory origin. Although final proof by retrograde tracing cannot be presented in man, this conclusion is supported by experimental evidence in laboratory animals. The myelinated immunoreactive axons correspond to chemoreceptor A-fibres whereas the classification of the large unmyelinated immunoreactive axons has yet to be established. The lack of immunoreactivity to the dopamine-synthesizing enzyme, aromatic-L-amino-acid-decarboxylase, in this fibre type does not support the view of dopamine being the primary transmitter of chemoreceptor afferents.

Characterization of a human-human hybridoma antibody, C-OU1, directed against a colon tumor-associated antigen

The human hybridoma cell line, B9165, was obtained after fusion of lymphocytes from lymph nodes draining the tumor region in a patient with adenocarcinoma of the colon with the human B-lymphoblastoid cell line WI-L2-729-HF2 (729-HF2). B9165 secretes the human monoclonal antibody, C-OU1 (IgM, kappa). Immunocytochemical and immunohistochemical analysis showed that the antibody bound to a differentiation antigen. Electron microscopy of colonic adenocarcinoma cells, intact tumor and colonic epithelium by the immunogold technique demonstrated that the C-OU1 antibody reacted with a molecule associated with areas of disruption of the intermediate filaments in the cytoplasm of the tumor cells. No reaction was seen with intermediate filaments in normal colonic epithelium. The molecular weight of the antigen was shown to be 43 Kda by SDS-PAGE and Western blotting of tumor extracts, and isoelectric focusing of sonicated extracts demonstrated reaction with molecular species of pI 5.4-6.2. These findings suggest that the C-OU1 antigen is a modified cytokeratin 18. The B9165 cell line has proved to be quite stable, and the antibody is of potential clinical value. Its usefulness for localizing tumors in patients is being investigated.

Intermediate filament antigens of 60 and 65 kDa in the nuclear matrix of plants: their detection and localization

Although the presence of a matrix in plant nuclei has been reported, major questions remain about its structural and biochemical features. We have used an intermediate filament antibody of broad specificity to explore whether Daucus carota (carrot) nuclei and nuclear matrices contain intermediate filament/lamin antigens and, if so, where specifically they are localized. SDS-PAGE and Western blotting revealed two bands, at 60 and 65 kDa, that were highly immunoreactive with the intermediate filament antibody (IFA) of Pruss et al. (1981, Cell 27, 419-428). This pattern was observed consistently, not only with carrot cell-free nuclei and nuclear matrices, but also with nuclear preparations from Vicia faba (broad bean) and Pisum sativum (pea). Immunofluorescence studies with whole carrot nuclei localized the IFA antigens to the nucleoplasm and disclosed no accentuated peripheral labeling. Agarose-embedded nuclear matrices showed not only fluorescence throughout the nucleoplasm but also heavy labeling surrounding the nucleoli and suggestions of peripheral labeling. At the ultrastructural level, immunogold results from pre- and postembedment treatments supported the conclusion that IFA antigens occur throughout the nucleoplasm, with possibly a slight concentration at the periphery. These combined results provide substantial evidence that plant nuclei and their matrices possess at least two major intermediate filament antigens with molecular weights characteristic of animal lamins. Whether or not these antigens represent plant lamins, their nonperipheral localization hints at significant differences among the eukaryotic kingdoms in nuclear organization.

Immunocytochemical and ultrastructural studies of neuronal and oligodendroglial cytoplasmic inclusions in multiple system atrophy. 1. Neuronal cytoplasmic inclusions

Neuronal alterations in five cases of multiple system atrophy (MSA) were investigated histologically, immunocytochemically and ultrastructurally. Argentophilic neuronal cytoplasmic inclusions (NCIs) were observed in all cases. They were distributed, in order of decreasing frequency, in the pontine nucleus, striatum, subiculum, amygdala, hippocampus, dentate fascia, substantia nigra and inferior olivary nucleus. Anti-ubiquitin antibodies visualized many thickened neurites in the degenerating gray matter as well as NCIs. Some NCIs were also recognized by anti-phosphorylated neurofilament antibodies. Ultrastructurally, NCIs consisted of a meshwork of granule-associated filaments, the diameter ranging from 18 to 28 nm, that were mixed with neurofilaments. The granule-associated filaments were also present in the axoplasm of myelinated fibers. Our studies demonstrate widespread distribution of NCIs in the central nervous system of MSA. The same pathological process that forms the granule-associated filaments in axons may also be responsible for the formation of ubiquitin-positive thickened neurites. These axonal alterations, as well as neuronal perikaryal changes, may play an important role in the impaired neuronal function in MSA.

Effect of the substrate on neurofilament phosphorylation in mixed cultures of rat embryo spinal cord and dorsal root ganglia

The effect of the substrate on neurofilament phosphorylation was studied in primary cultures of spinal cord and dorsal root ganglia dissociated from 15-day-old rat embryos. On polylysine and Primaria substrates, spinal cord neurons formed aggregates connected by bundles of neurites. (Primaria dishes have a modified plastic surface with a net positive charge). On both polylysine and Primaria substrates, spinal cord neurons were stained with neurofilament monoclonal antibodies reacting with phosphorylated epitopes appearing early in rat embryo development, i.e. soon after neurofilament expression. Conversely, immunoreactivity with antibodies recognizing late phosphorylation events was only observed on Primaria substrates. As reported by many investigators, fibronectin and laminin were excellent substrates for dorsal root ganglia neurons in culture. However, on both laminin and fibronectin substrates immunoreactivity with antibodies recognizing late phosphorylation events, was only observed on Primaria substrates. As reported by many investigators, fibronectin and laminin were excellent substrates for dorsal root ganglia neurons in culture. However, on both laminin and fibronectin substrates immunoreactivity with antibodies recognizing late phosphorylation events, only occurred after several days in culture, at a time when non-neuronal cells (mainly astrocytes) had formed a confluent monolayer.

Neurofilament epitopes in thymoma and antiaxonal autoantibodies in myasthenia gravis

Expression by neoplastic thymic epithelial cells of acetylcholine-receptor (AChR) epitopes is associated with the presence of AChR autoantibodies and the development of myasthenia gravis. We studied thymic tumours from patients with and without myasthenia gravis for the expression of neurofilament epitopes by immunohistochemistry with four monoclonal antibodies. There was very little antibody binding in control samples (healthy thymus, or thymitis) or in medullary and mixed thymomas, but neurofilament epitopes were strongly expressed in all cortical thymomas and thymic carcinomas. In addition, the frequency of serum autoantibodies against axons was significantly higher among myasthenic patients with thymic epithelial tumours than among age-matched controls (7/10 vs 3/50; p less than 0.01).

Detection of antibodies to human nerve antigens in sera from leprosy patients by ELISA

Anti-neural antibodies have been implicated to play a role in the pathogenesis of nerve damage in leprosy patients. To find the relationship between anti-neural antibodies and clinical findings, we attempted to detect antibodies against neurofilament-enriched proteins by ELISA in sera from leprosy patients. Of 289 sera from leprosy patients, 74 (25.6%) had significant anti-neural antibodies; in contrast, 1 (5.0%) of 20 tuberculosis patients and 11 (7.1%) of 154 controls were seroreactive to nerve antigen. When clinical types were considered, a significant level of anti-neural IgG antibodies was detectable in 53 (30.1%) of 176 sera from lepromatous patients compared with 21 (18.6%) of 113 sera from tuberculoid patients, indicating that lepromatous patients were more likely to be seropositive to nerve antigens in ELISA. Some of the ELISA-reactive sera showed antibody reactivity with 38-kD, 40-kD and 43-kD nerve antigens in Western blotting analysis. There was no apparent correlation between seroreactivity to nerve antigens and bacterial load in leprosy patients. Although there was no statistical significance, anti-neural antibodies were detectable more often among the patients on chemotherapy than the untreated and among the patients with erythema nodosum leprosum than without. The results, therefore, suggest that anti-neural antibodies are elicited during the course of leprosy and may be associated with the extensiveness of nerve involvement in the patients.

The structure of two IgMs showing different activity from a patient with Waldenstrom's macroglobulinaemia

The two monoclonal IgMs (IgM1 and IgM2) were characterized from a patient Waldenström's macroglobulinaemia that resulted in a gammapathy. Heavy and light chains were isolated from the IgM. The complete primary structure of the two light chains and the NH2-terminal region of the two heavy chain molecules were determined. The sequence data indicated that the heavy and light chains from both IgMs belong to the same (III and II) lambda subgroups. By testing their antibody activity it was found by immunofluorescence and immunoblotting that only IgM2 reacts with an intermediate filament protein.

Phosphorylation-dependent neurofilament epitopes are reduced at the node of Ranvier

Neurofilaments in axons are highly phosphorylated at multiple sites on the 200 kDa neurofilament (neurofilament-H) and 160 kDa (neurofilament-M) subunit peptides. We used a panel of monoclonal and polyclonal antibodies against distinct neurofilament epitopes to study the distribution of these epitopes along the axons of large myelinated fibres in rat sciatic nerve using quantitative electron microscopic immunocytochemistry with colloidal gold. Antibodies specific for phosphorylated epitopes on neurofilament-H showed a 60% reduction in density of immunoreactivity at the node of Ranvier, compared to the internodal axon. Antibodies directed against neurofilament-M, which recognized phosphorylated epitopes preferentially, showed a 40% reduction in density of immunoreactivity at the node. Following dephosphorylation of the neurofilaments in tissue sections by alkaline phosphatase treatment, antibodies which recognized dephosphorylated forms of neurofilament-H showed no reduction in density of immunoreactivity at the node. Similarly, an antibody directed against the 70 kDa subunit (neurofilament-L), showed no reduction in density of immunoreactivity at the node. An antibody against tubulin also showed no decrease in the density of immunoreactivity at the node of Ranvier. Tubulin immunoreactivity was similar in myelinated and unmyelinated fibres. In contrast to phosphorylated neurofilament epitopes, immunoreactivity was much greater in myelinated than unmyelinated fibres. These results suggest that the degree of phosphorylation of neurofilament-H and neurofilament-M subunits is reduced at the node of Ranvier, in comparison to internodal neurofilaments, and imply that a post-translational modification of neurofilaments must occur along the length of the axon at the node.