Nonmyeloablative conditioning generates autoantigen-encoding bone marrow that prevents and cures an experimental autoimmune disease.

Autoimmune diseases result from chronic targeted immune responses that lead to tissue pathology and disease. The potential of autologous hematopoietic stem cells transplantation as a treatment for autoimmunity is currently being trialled but disease relapse is an issue. We have previously shown in a mouse model of experimental autoimmune encephalomyelitis (EAE) that the transplantation of bone marrow (BM) transduced to encode the autoantigen myelin oligodendrocyte glycoprotein (MOG) can prevent disease induction. However these studies were performed using lethal irradiation to generate BM chimeras and a critical factor for translation to humans would be the ability to utilize low toxic preconditioning regimes. In this study, treosulfan was used as a nonmyeloablative agent to generate BM chimeras encoding MOG and assessed in models of EAE induction and reversal. We find that treosulfan conditioning can promote a low degree of chimerism that is sufficient to promote antigen specific tolerance and protect mice from EAE. When incorporated into a curative protocol for treating mice with established EAE, nonmyeloablative conditioning and low chimerism was equally efficient in maintaining disease resistance. These studies further underpin the potential and feasibility of utilizing a gene therapy approach to treat autoimmune disease.

Non-myeloablative transplantation of bone marrow expressing self-antigen establishes peripheral tolerance and completely prevents autoimmunity in mice.

Myeloablative transplantation of bone marrow (BM) engineered to express myelin oligodendrocyte glycoprotein (MOG) establishes central intrathymic tolerance and completely prevents MOG-induced experimental autoimmune encephalomyelitis (EAE) in mice. Here we asked whether non-myeloablative transplantation of MOG expressing BM (pMOG-bone marrow transplantation (BMT)) can also provide the same protection. Using stepwise reduction of irradiation doses, 275 cGy irradiation with pMOG-BMT protected 100% of mice from EAE development even with two subsequent re-challenge with MOG. Irradiation doses <275 cGy produced dose-dependent partial protection with significant disease protection still evident at 50 cGy. Splenocytes from 275 cGy recipients proliferated to MOG stimulation in vitro, indicating that MOG-reactive cells are present in the periphery but failed to induce disease. MOG-stimulated splenocytes produced little or no interleukin-17, interferon-γ, granulocyte-monocyte colony stimulating factor and tumor necrosis factor-α compared with EAE control. Adoptive transfer of CD4 T cells from EAE-resistant mice into Rag2(-/-) mice devoid of MOG expression resulted in MOG-induced EAE in ~74% of mice. Treatment of EAE-resistant mice with anti-programmed death 1 (PD-1) monoclonal antibody-induced EAE in 67% of mice. We conclude that non-myeloablative transplantation of self-antigen expressing BM induces robust peripheral tolerance that completely prevented EAE development. Our findings implicate clonal anergy and the PD-1 pathway in the maintenance of peripheral tolerance.

Prednisolone promotes remission and gastric mucosal regeneration in experimental autoimmune gastritis.

A cardinal feature of organ-specific autoimmunity is destructive pathology in the target organ. In human and experimental models of autoimmune gastritis, mononuclear cell infiltration and cellular destruction in the gastric mucosa are disease hallmarks. Strategies to cure autoimmune disease must not only establish immunological tolerance to autoantigen, but also rid the organ of pathogenic autoreactive cells. The present study has assessed the effect of prednisolone treatment in clearing the inflammatory infiltrate in experimental autoimmune gastritis and in preventing disease relapse in athymic compared with euthymic mice. Experimental autoimmune gastritis was induced by neonatal thymectomy or by transgenic expression of GM-CSF (PC-GMCSF mice). Groups of mice were treated with prednisolone (10 mg/kg per day) for 10 weeks or with prednisolone for 10 weeks followed by 10 weeks without prednisolone. Stomachs were examined for gross morphological changes, and by histology and immunohistochemistry for composition of inflammatory infiltrate and gastric mucosal integrity. Autoantibody to gastric H+/K+ ATPase was determined by ELISA. Prednisolone promoted remission of gastritis in both mouse models of experimental autoimmune gastritis, evident by reduction in stomach size, clearing of gastric inflammatory infiltrate, and regeneration of the gastric mucosa. Prednisolone withdrawal resulted in disease relapse in all PC-GMCSF mice, whereas approximately 40% of neonatal thymectomy mice retained normal stomach morphology and remained free of gastric pathology. It is concluded that prednisolone promotes remission and gastric mucosal regeneration in experimental autoimmune gastritis. Prolonged remission of autoimmune gastritis in some athymic mice suggests a role for the thymus in disease relapse.

Experimental autoimmune gastritis: mouse models of human organ-specific autoimmune disease.

Experimental autoimmune gastritis (EAG) is an excellent model of human autoimmune gastritis, the underlying cause of pernicious anaemia. Murine autoimmune gastritis replicates human gastritis in being characterized by a chronic inflammatory mononuclear cell infiltrate in the gastric mucosa, destruction of parietal and zymogenic cells, and autoantibodies to the alpha-and beta-subunits of the gastric H+/K+ ATPase. Disease is induced strain specifically in gastritis-susceptible BALB/c mice by methods with a greater variety than those for most other experimental autoimmune diseases. The disease is induced in the regional gastric lymph node in which pathogenic CD4+ T cells are recruited. The model provides an excellent illustration of regulation by CD4+CD25+T cells, and, indeed, the removal of such regulatory cells, e.g., by neonatal thymectomy, is thought to be a major mechanism by which disease can develop. The culprit T helper type 1 (Th1) CD4+ T cells recognize either the alpha- or beta-subunits of the gastric H+/K+ ATPase, but the beta-subunit appears to be the initiating autoantigen, while the alpha-subunit may have a role in perpetuating disease. Since no specific environmental modifiers are identifiable, the origins of the disease are intrinsic; this is illustrated by the capacity of a cytokine (GM-CSF)-dependent inflammatory stimulus in the stomach to initiate EAG, according to a transgenic model in which thymectomy is dispensible. Thus, EAG is an exquisite model for a reductionist analysis of the multiple elements that in combination induce autoimmunity in humans.

Local transgenic expression of granulocyte macrophage-colony stimulating factor initiates autoimmunity.

Mechanisms leading to breakdown of immunological tolerance and initiation of autoimmunity are poorly understood. Experimental autoimmune gastritis is a paradigm of organ-specific autoimmunity arising from a pathogenic autoimmune response to gastric H/K ATPase. The gastritis is accompanied by autoantibodies to the gastric H/K ATPase. The best characterized model of experimental autoimmune gastritis requires neonatal thymectomy. This procedure disrupts the immune repertoire, limiting its usefulness in understanding how autoimmunity arises in animals with intact immune systems. Here we tested whether local production of GM-CSF, a pro-inflammatory cytokine, is sufficient to break tolerance and initiate autoimmunity. We generated transgenic mice expressing GM-CSF in the stomach. These transgenic mice spontaneously developed gastritis with an incidence of about 80% after six backcrosses to gastritis-susceptible BALBc/CrSlc mice. The gastritis is accompanied by mucosal hypertrophy, enlargement of draining lymph nodes and autoantibodies to gastric H/K ATPase. An infiltrate of dendritic cells and macrophages preceded CD4 T cells into the gastric mucosa. T cells from draining lymph nodes specifically proliferated to the gastric H/K ATPase. CD4 but not CD8 T cells transferred gastritis to nude mouse recipients. CD4(+) CD25(+) T cells from the spleen retained anergic suppressive properties that were reversed by IL-2. We conclude that local expression of GM-CSF is sufficient to break tolerance and initiate autoimmunity mediated by CD4 T cells. This new mouse model should be useful for studies of organ-specific autoimmunity.

Immunopathology of autoimmune gastritis: lessons from mouse models.

Autoimmune gastritis in humans is a chronic inflammatory disease of the stomach accompanied by specific destruction of gastric parietal and zymogenic cells resulting in pernicious anemia. Human gastritis can be accurately reproduced in mice and is characterised by autoantibodies to the alpha- and beta-subunits of the gastric H/K ATPase (the enzyme responsible for gastric acid secretion) and cellular destruction of parietal and zymogenic cells within the gastric gland. Studies with these mouse models have given us our current concepts of the immunopathogenesis of the gastritis. Mouse models have shown that a T cell response is generated to the alpha- and beta-subunits of the H/K ATPase and that an immune response to the beta-subunit seems to be required for disease initiation. Using these models, we have defined key events associated with a damaging autoimmune response to the gastric H/K ATPase. The mechanisms associated with the cellular destruction associated with autoimmune gastritis are not know, but may involve signaling through death inducing pathways such as the Fas/FasL and TNF/TNFR pathways. This knowledge should permit us to develop strategies to prevent and treat the gastritis.

The causative H+/K+ ATPase antigen in the pathogenesis of autoimmune gastritis.

The gastric H+/K+ ATPase is the causative autoantigen recognized by CD4+ T cells that mediate autoimmune gastritis. Pathogenic CD4+ T cells are regulated by CD25+CD4+ T cells. Here, it is proposed that waves of activation and migration of antigen presenting cells and CD4+ T cells to and from the target organ and draining lymph node result in tissue damage.

Tolerance and autoimmunity to a gastritogenic peptide in TCR transgenic mice.

The catalytic alpha and glycoprotein beta subunits of the gastric H/K ATPase are major molecular targets in human and mouse autoimmune gastritis. We have previously shown that the H/K ATPase beta subunit is required for the initiation of mouse gastritis and identified a gastritogenic H/K ATPase beta subunit peptide (H/Kbeta253-277). Here we report the generation of MHC class II-restricted TCR transgenic mice using V(alpha)9 and V(beta)8.3 TCR chains with specificity for the gastritogenic H/Kbeta253-277 peptide. We found an 8-fold reduction in CD4(+) T cells in the thymus of the transgenic mice. Despite the reduction in intrathymic CD4(+) T cells, V(beta)8. 3-expressing T cells comprised the majority (>90%) of peripheral spleen and lymph node T cells. These peripheral T cells retained their capacity to proliferate in vitro to the H/Kbeta253-277 peptide. Using the responsive T cells, we have restricted the gastritogenic T cell epitope to H/Kbeta261-274. Despite the capacity of the peripheral T cells to proliferate in vitro to the peptide, the majority ( approximately 80%, 13 of 16) of transgenic mice remained free of gastritis while a minority (20%, three of 16) spontaneously developed an invasive and destructive gastritis. Our results confirm that H/Kbeta261-274 is a gastritogenic peptide. The data also suggest that CD4 T cell tolerance to the gastritogenic peptide in the transgenic mice is maintained by a combination of intrathymic and peripheral tolerance mechanisms.

Defining T cell receptors which recognise the immunodominant epitope of the gastric autoantigen, the H/K ATPase beta-subunit.

We have previously shown that autoimmune gastritis can be elicited in mice by immunisation with the gastric parietal cell H/K ATPase alphabeta heterodimer, and, furthermore, have identified the H/K ATPase beta-subunit epitope, H/Kbeta253-277 as the dominant epitope of the gastric H/K ATPase. Using gastric H/K ATPase-immunised mice, here we have generated two T cell hybridomas specific for the H/Kbeta253-277 peptide, namely 4B11.F4.5 and 1E4.C1. Hybridoma 4B11.F4.5 uses Valpha8 and Vbeta8.2 TCR chains and 1E4.C1 uses Valpha9 and V1beta8.3 chains. Although both hybridomas are specific for H/Kbeta253-277, T cell assays using overlapping 14-mers of the 25-mer epitope showed that the two autoreactive TCRs recognise different regions of the 25-mer. The TCR from 1E4.C1 has been used to generate a TCR beta-chain transgenic mouse. >80% of peripheral CD4+ T cells utilise the Vbeta8.3 transgene. As expected, 1E4-TCR beta-chain transgenic mice are susceptible to neonatal thymectomy induced autoimmune gastritis. While none of the 1E4-TCR beta chain transgenic mice spontaneously developed a destructive gastritis, a minority (20%) of the transgenic mice developed a non-invasive and non-destructive gastritis. This suggests that the pathogenic T cells are maintained in a tolerant state in the periphery of the transgenic mice.

Spontaneous autoimmune gastritis in C3H/He mice: a new mouse model for gastric autoimmunity.

Autoimmune gastritis is the underlying pathological lesion of pernicious anemia in humans. The lesion is characterized by a chronic inflammatory infiltrate in the gastric mucosa with loss of parietal and zymogenic cells. It is associated with circulating autoantibodies to the gastric H/K-ATPase, the enzyme responsible for acidification of gastric juice. Experimental models of autoimmune gastritis have previously been produced in mice after a variety of manipulations, including thymectomy. Here we report for the first time a spontaneous mouse model of autoimmune gastritis in C3H/He mice. The spontaneous gastritis is also accompanied by circulating autoantibodies to the gastric H/K-ATPase. The spontaneous mouse model should be useful for studies directed toward the immunopathogenesis and treatment of autoimmune gastritis.

Expression of the gastric H/K-ATPase alpha-subunit in the thymus may explain the dominant role of the beta-subunit in the pathogenesis of autoimmune gastritis.

The two subunits of the gastric H/K ATPase, namely the catalytic alpha-subunit and the glycoprotein beta-subunit, are the major targets of parietal cell autoantibodies associated with human and murine autoimmune gastritis. The murine disease induced by neonatal thymectomy is T cell-mediated. We have previously shown that transgenic expression of the H/K ATPase beta-subunit gene in the thymus prevented the development of autoimmune gastritis induced by thymectomy. However, little is known of the contribution of the H/K ATPase alpha-subunit in disease development. Here, we show that (1) in contrast to the gastric H/K ATPase beta-subunit, the alpha-subunit gene is expressed in normal BALB/c thymus. (2) transgenic expression of the gastric H/K ATPase alpha-subunit gene in the thymus failed to prevent the development of autoimmune gastritis and (3) normal BALB/c and transgenic mice expressing the alpha-subunit in the thymus develop autoimmune gastritis following immunisation with purified murine gastric H/K ATPase, whereas transgenic mice expressing the beta-subunit in the thymus do not. We propose that the expression of the H/K ATPase alpha-subunit in the normal thymus may account for the predominant role of the beta-subunit in the development of autoimmune gastritis induced either by thymectomy or by immunisation with the ATPase.

Atrophic gastric changes in both Helicobacter felis and Helicobacter pylori infected mice are host dependent and separate from antral gastritis.

BACKGROUND/AIMS: The role of host factors has been neglected in studies of the pathogenesis of Helicobacter associated disease. The aim of this study was to assess the response of different mouse strains to infection with a single strain of Helicobacter felis. METHOD: Six strains of inbred mice were infected with the identical H felis culture and were killed at one month, two months, and six months after infection to assess histopathological changes. In addition, two strains of mice were infected with a mouse adapted strain of H pylori and examined at six months after infection. RESULTS: In SJL, C3H/He, DBA/2, and C57BL/6 infected mice, severe to moderate chronic active gastritis was observed only in the body of the stomach, which increased in severity over time with specialised cells in the body glands being replaced. As the severity of this damage in the body increased and atrophic changes were seen, the level of bacterial colonisation of the antrum decreased. In contrast, in BALB/c and CBA mice, there was only mild gastritis in the antrum, no remarkable changes were detected in their body mucosa, and no atrophy was seen over time. In both these strains of mice, heavy bacterial colonisation was seen, which tended to increase over the period of the experiment. Of particular importance in this experiment was that bacterial colonisation was mainly restricted to the antrum yet the atrophy, when present, was only observed in the body of the stomach. H pylori infected C3H/He mice showed moderate colonisation of the antrum, which persisted up to six months with little development of atrophy. In contrast, H pylori in C57BL/6 mice showed excellent colonisation of the antrum at two months but six months after infection there was moderate to severe body atrophy, which was associated with a loss of bacteria from the antrum. CONCLUSIONS: These findings challenge current concepts of the development of Helicobacter induced atrophy in that active chronic gastritis of antrum or the body mucosa, or both, is not a prerequisite. They also suggest an autoimmune basis for the pathology although no autoantibody or antibody to the H+/K+ ATPase was detected. Loss of infecting helicobacters from the stomach together with development of an atrophic gastritis in the body of the stomach is similar to the pattern found in certain H pylori infected human subjects.

Analysis of mononuclear cell infiltrate and cytokine production in murine autoimmune gastritis.

BACKGROUND & AIMS: Murine autoimmune gastritis, induced by day-3 thymectomy, is characterized by cellular infiltrates and circulating autoantibodies to gastric hydrogen/potassium adenosine triphosphatase. The aim of this study was to analyze the cellular infiltrates and cytokines in autoimmune gastritis. METHODS: Stomachs and blood samples from day-3 thymectomized BALB/c mice were obtained from 2 to 12 weeks after thymectomy for analysis. RESULTS: At 4 weeks, the gastritic infiltrates were composed of macrophages and CD4+ T cells, accompanied by major histocompatibility complex class II expression on gastric epithelial cells. Mucosal B cells, scant at 4 weeks, were abundant at 8 weeks, coincident with the peaking of autoantibodies to gastric hydrogen/potassium adenosine triphosphatase. CD8+ T cells increased marginally during the 12 weeks. Mononuclear cells from diseased stomachs transferred gastritis to nu/nu recipients. At 4 weeks, interleukins 2, 3, 5, 6, and 10; interferon gamma; tumor necrosis factor alpha; and granulocyte-macrophage colony-stimulating factor were detected in gastritic mucosa, but interleukin 4 was not. CONCLUSIONS: The early lesion of autoimmune gastritis is composed of macrophages and CD4+ T cells with major histocompatibility complex class II expression in gastric epithelial cells. Autoantibody production is a late event. Our results are consistent with a lesion mediated by CD4+ T cells producing a mix of Th1- and Th2-type cytokines.

Expression of a gastric autoantigen in pancreatic islets results in non-destructive insulitis after neonatal thymectomy.

Autoimmune gastritis, induced by day-3 thymectomy of BALB/c mice, is a destructive CD4+ T cell-mediated disease characterized by leukocyte infiltrates in the gastric mucosa, loss of parietal and chief cells and anti-gastric H/K ATPase autoantibodies. Our previous studies have indicated that a T cell response to the H/K ATPase beta subunit is required for the onset of autoimmune gastritis (Alderuccio, F., Toh, B. H., Tan, S. S., Gleeson, P. A. and van Driel, I. R., J. Exp. Med. 1993. 178: 419). To determine whether a response to the beta subunit autoantigen is alone sufficient to induce autoimmunity, or whether other tissue-specific factors are required, we have generated transgenic mice expressing the gastric H/K ATPase beta subunit in beta islet cells of the pancreas (RIP-H/K beta). RIP-H/K beta mice developed autoimmune gastritis and insulitis after day-3 thymectomy. Significantly, insulitis, observed as a peri-islet infiltrate, was only detected in thymectomized mice with autoimmune gastritis. There was no apparent immune destruction of the pancreas as insulitis did not progress to invasion of the islets or diabetes. Double transgenic mice, expressing the gastric H/K ATPase beta subunit in the thymus and in the pancreas, were protected from both gastritis and insulitis after day-3 thymectomy. Therefore, insulitis in the RIP-H/K beta mice appears to be dependent on a T cell response to the H/K ATPase beta subunit. This is the first example where an organ-specific initiating autoantigen has been expressed in another peripheral tissue. Autoimmune destruction in the stomach, but not the pancreas, indicates that tissue-specific factors play a fundamental role in the development of organ-specific autoimmunity.

Organ-specific autoimmunity induced by adult thymectomy and cyclophosphamide-induced lymphopenia.

Autoimmune gastritis, a CD4+ T cell-mediated organ-specific autoimmune disease, can be induced by thymectomy of neonatal, but not of older, BALB/c mice. Here we have shown that autoimmune gastritis can also be induced in 6-8-week-old BALB/c mice by thymectomy combined with a single dose of cyclophosphamide (300 mg/kg). This treatment reduced the numbers of splenic T and B cells approximately 25-fold. However, by 8 days after treatment, the number of splenic lymphocytes had returned to normal adult levels. Approximately 50% of treated mice developed autoimmune gastritis after 10-12 weeks. These mice had mononuclear cellular infiltrates within the gastric mucosa and serum autoantibodies to the alpha and beta subunits of the gastric H+/K+ ATPase. Transgenic mice, expressing the gastric H+/K+ ATPase beta-subunit in the thymus (Alderuccio, F., Toh, B. H., Tan, S. S., Gleeson, P. A. and van Driel, I. R., J. Exp. Med. 1993. 178: 419), did not develop autoimmune gastritis after the adult thymectomy/cyclophosphamide treatment. Thus a T cell response to the H+/K+ ATPase beta-subunit is likely to be required for the onset of gastritis. These observations suggest that pathogenic autoreactive T cells exist in the periphery of normal adult mice and that autoimmunity can be induced by the activation of these autoreactive T cells following transient lymphopenia. Cyclophosphamide-treatment of adult mice without thymectomy did not induce autoimmune gastritis, suggesting thymic regulation of these pathogenic T cells.

A novel method for isolating mononuclear cells from the stomachs of mice with experimental autoimmune gastritis.

Autoimmune gastritis induced in BALB/c mice by neonatal thymectomy is a CD4+ T cell-mediated disease. The disease is characterised by mononuclear cell infiltrates in the gastric mucosa, loss of gastric parietal and chief cells and autoantibodies to the gastric H/K ATPase. Here we describe a simple non-enzymatic method for isolating cellular infiltrates from stomachs of gastric mice by injection of medium directly into stomach walls, causing swelling and rupture. Using this method, large numbers of viable lymphocytes were released from stomachs for analysis by flow cytometry. An 8.3 fold increase in the total number of lymphocytes from diseased stomachs compared to normal controls was observed. Total cell numbers of CD4+ and B cells were increased 4.8 fold and 39.5 fold respectively, in diseased stomachs compared with controls. No change was observed in the CD8+ T cell population. This method will allow detailed quantitative analysis of cellular infiltrates during the development of the gastric lesion and enrichment of pathogenic T cells for analysis and cloning. This procedure may have general application for the isolation of cellular infiltrates from lesion sites of other organs.

A new chromosomal protein essential for mitotic spindle assembly.

Assembly of the mitotic spindle, the machinery responsible for chromosomal segregation, is regulated by Cdc2 kinase and requires mitotic chromatin. However, the molecular identity of the kinase substrate and chromatin factor is unknown. Here we have cloned a human complementary DNA encoding an evolutionarily conserved chromosomal protein of relative molecular mass 47,000 (M(r) 47K) which has three consensus motifs for Cdc2 kinase-mediated phosphorylation. The protein is phosphorylated only during mitosis and is associated with polypeptides having M(r)s of 31K, 67K and 200K. Mitotic arrest is induced by antisense messenger RNA or by affinity-purified autoantibody. In the arrested cells, the chromosomes remain unsegregated and the mitotic spindle is absent. We propose that the chromosomal protein is activated by phosphorylation at the interphase/mitosis transition by Cdc2 kinase, and that the protein, alone or as a complex, is a previously unidentified Cdc2 kinase substrate and chromatin factor necessary for spindle assembly.

An autoimmune disease with multiple molecular targets abrogated by the transgenic expression of a single autoantigen in the thymus.

Many autoimmune diseases are characterized by autoantibody reactivities to multiple cellular antigens. Autoantigens are commonly defined as targets of the autoimmune B cell response, but the role, if any, of these autoantigens in T cell-mediated autoimmune diseases is generally unknown. Murine experimental autoimmune gastritis is a CD4+ T cell-mediated organ-specific autoimmune disease induced by neonatal thymectomy of BALB/c mice. The murine disease is similar to human autoimmune gastritis and pernicious anemia, and is characterized by parietal and chief cell loss, submucosal mononuclear cell infiltrates, and autoantibodies to the alpha and beta subunits of the gastric H/K ATPase. However, the specificity of T cells that cause the disease is not known. To examine the role of the H/K ATPase in this T cell-mediated disease, transgenic mice were generated that express the beta subunit of the H/K ATPase under the control of the major histocompatibility complex class II I-Ek alpha promoter. We show that transgenic expression of the gastric H/K ATPase beta subunit specifically prevents the onset of autoimmune gastritis after neonatal thymectomy. In addition, thymocyte transfer experiments suggest that tolerance of pathogenic autoreactive T cells is induced within the thymus of the transgenic mice. We conclude that the beta subunit of the gastric H/K ATPase is a major T cell target in autoimmune gastritis and that thymic expression of a single autoantigen can abrogate an autoimmune response to multiple autoantigens.

Alpha and beta subunits of the gastric H+/K(+)-ATPase are concordantly targeted by parietal cell autoantibodies associated with autoimmune gastritis.

We have previously shown that parietal cell autoantibodies predominantly react with a 60-90 kDa gastric autoantigen, subsequently identified as the beta subunit of the gastric H+/K(+)-ATPase (EC 3.6.1.3) (proton pump) whereas Karlsson et al showed that these autoantibodies primarily target the 95 kDa alpha subunit of the pump. In view of these discordant results, we have reassessed the reactivity of parietal cell autoantibodies with the two subunits of the gastric H+/K(+)-ATPase. We show here that all 26 parietal cell autoantibody-positive sera immunoblot both subunits under appropriate, but mutually exclusive, conditions. Thus, reactivity of anti-parietal cell autoantibodies with the 95 kDa alpha subunit is optimal when the SDS-PAGE is carried out with samples which are reduced but not boiled. Whereas reactivity with the 60-90 kDa beta subunit is optimal with samples which are boiled but not reduced. Autoantibody reactivity with the beta subunit is critically dependent on the presence of a full complement of N-linked glycans since partially deglycosylated protein, and recombinant beta subunit expressed in COS cells, bearing high mannose N-glycans, failed to bind to the autoantibody. These studies also suggest that B cell auto-epitopes are located on the lumenal domain of the beta subunit. Reactivity of parietal cell autoantibodies with a bacterial fusion protein incorporating the catalytic cytoplasmic domain of the alpha subunit suggests the presence of auto-epitopes in this region of the molecule.

Molecular characterization of an autoantigen of PM-Scl in the polymyositis/scleroderma overlap syndrome: a unique and complete human cDNA encoding an apparent 75-kD acidic protein of the nucleolar complex.

About 50% of patients with the polymyositis/scleroderma (PM-Scl) overlap syndrome are reported to have autoantibodies to a nuclear/nucleolar particle termed PM-Scl. The particle is composed of several polypeptides of which two have been identified as autoantigens. In this report, human cDNA clone coding for the entire 75-kD autoantigen of the PM-Scl particle (PM-Scl 75) was isolated from a MOLT-4 lambda gt-11 library. The deduced amino acid sequence of the cDNA clone represented a protein of 355 amino acids and 39.2 kD; the in vitro translation product of this cDNA migrated in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) at approximately 70 kD. The aberrant migration of the polypeptide in SDS-PAGE was shown to be related to the COOH half that was rich in acidic residues. Authenticity of the cDNA coding for PM-Scl 75 was shown by immunoreactivity of PM-Scl sera with in vitro translation products and recombinant fusion proteins encoded by the cDNA. In addition, rabbit antibodies raised to recombinant fusion protein reacted in immunofluorescence, immunoblotting, and immunoprecipitation with the characteristic features displayed by human anti-PM-Scl sera.