Mechanisms Of Autoantibody Production Research Articles

Apoptosis-induced translocation of centromere protein F in its corresponding autoantibody production in hepatocellular carcinoma

ABSTRACT Serum autoantibodies against tumor-associated antigen have important value in the early diagnosis of hepatocellular carcinoma (HCC), but the mechanism of autoantibody production is poorly understood. We previously showed that autoantibodies against the centromere protein F (CENPF) may be useful as an early diagnostic marker for HCC. Here we explored the mechanism of cell apoptosis-based CENPF autoantibody production and verified the correlation of CENPF autoantibody level with HCC development. We demonstrated that CENPF was overexpressed and aberrantly localized throughout the nuclei and cytoplasm in human HCC cells compared with hepatic cells. CENPF overexpression promoted the production of CENPF autoantibodies in a manner that correlated with tumor growth of mouse HCC model. During apoptosis of HCC cells, CENPF protein translocated to apoptotic vesicles and relocalized at the cell surface. Through isolating apoptotic components, we found apoptotic body and blebs with lower CD31 and CD47 expression more effectively induced DC phagocytosis and maturation compared with apoptotic intact cells in vitro, and this DC response was independent of CENPF expression. Moreover, injection of mice with apoptotic bodies and blebs effectively induced an immune response and the production of CENPF-specific antibodies. Our findings provide a first elucidation of mechanisms underlying the CENPF autoantibody production via cell apoptosis-induced CENPF translocation, and demonstrate a direct correlation between CENPF autoantibody levels and HCC progression, suggesting the potential of CENPF autoantibody as an HCC diagnostic marker.

Mechanisms of loss of immune tolerance in the production of antiplatelet autoantibodies in primary immune thrombocytopenia

Primary immune thrombocytopenia (ITP) is an organ-specific autoimmune hemorrhagic disease. The etiology of ITP is still unclear, but loss of immune tolerance to platelet surface antigens is considered as a fundamental cause of ITP. Therapeutic strategies that prevent the activation and proliferation of autoreactive cells have been suggested, which includes clearance of autoreactive cells (apoptosis), receptor editing, induction of anergy and extrinsic cellular suppression. Failure at any of these steps may lead to the production of autoantibodies against platelet and megakaryocyte glycoproteins. An improved understanding of the mechanisms for autoantibody production will provide theoretical basis for optimal diagnosis and treatment of ITP. Key words: ITP; Autoantibody; Immune tolerance

A re-evaluation of anti-NA-14 antibodies in patients with primary Sjögren’s syndrome: Significant role of interferon-γ in the production of autoantibodies against NA-14

Novel autoantibodies against nuclear antigen of 14 kDa (NA-14)/Sjögren’s syndrome nuclear antigen-1 (SSNA-1) are predominantly recognized in sera of patients with primary Sjögren’s syndrome (pSS). However, the detailed characteristics of the anti-NA-14 antibody remain unknown. Here, we sought to clarify the characteristics of anti-SSNA-1/NA-14 antibodies and the mechanisms of autoantibody production using sera from patients with connective tissue diseases (including pSS), autoimmune sera reacting with standard autoantigens (SS-A/Ro and/or SS-B/La, ds DNA, Scl-70 and Jo-1), and normal healthy controls (NHCs). Anti-NA-14 antibodies were predominantly recognized in sera from patients with pSS and in autoimmune sera reacting with thSS-A/Ro and/or -SS-B/Lo. Indirect immunofluorescence analysis showed that NA-14 was strongly expressed in mitotic-phase cells. Patients with pSS having anti-NA-14 antibodies exhibited significant elevation of serum IP-10 and BAFF compared to that in patients with pSS without anti-NA-14 antibodies and NHCs. Thus, our data demonstrated that anti-NA-14 antibodies could be classified as novel autoantibodies reacting with mitosis-related autoantigens predominantly recognized in pSS. Moreover, interferon-γ played an important role in the production of anti-NA-14 autoantibodies as patients with pSS having anti-NA-14 antibodies exhibited increased serum levels of IP-10 and BAFF.

A new mechanism of autoantibody production: antigen presentation of misfolded protein by MHC class II

Recently a new pathogenic mechanism for autoantibody production was proposed. Misfolded proteins bind to MHC class II in the endoplasmic reticulum and are processed to be presented at the cell surface. Misfolded proteins are not trimmed to peptides, but are presented as they are together with MHC class II molecules. Such misfolded protein/MHC class II complex can stimulate B cells, but not T cells, and will induce autoantibody production. One of such examples is the case of IgG heavy chain (IgGH). HLA class II can bind IgGH and presents it to the cell surface. Such IgGH/HLA class II complex can be recognized by rheumatoid factor. Surprisingly, RA susceptible HLA class II alleles can present IgGH efficiently, but RA resistant HLA class II alleles cannot. Therefore susceptibility to certain autoimmune diseases may be determined by the affinity of misfolded autoantigens to certain HLA class II alleles. Such new autoimmune mechanisms may explain the unexplained autoantibody production mechanisms.

Anti-argonaute2 (Ago2/Su) and -Ro antibodies identified by immunoprecipitation in primary anti-phospholipid syndrome (PAPS)

Objectives. Primary anti-phospholipid syndrome (PAPS) is an autoimmune condition defined by anti-phospholipid antibodies (aPL) and thrombotic or obstetric events. Some PAPS can evolve into systemic lupus erythematosus (SLE) during follow-up. Few studies systematically examined lupus autoantibodies and their clinical significance in PAPS. The aim of our study is to analyze the clinical and laboratory correlations with lupus-related autoantibodies, detected by immunoprecipitation (IP), a technique not yet systematically applied to investigate autoantibodies in this condition.Methods. Sera from 52 PAPS patients were screened by indirect immunofluorescence (IIF) antinuclear antibodies (ANA), IP of 35S-labeled K562 cell extract, and ELISA [anti-Argonaute2 (Ago2, Su), 60kRo, 52kRo, La, dsDNA)]. Anti-Ago2/Su positive sera were also tested for anti-GW bodies (GWBs) by IIF double staining, using rabbit anti-Rck/p54 serum.Results. First, 56% of PAPS patients (29/52) were ANA positive, mainly with speckled pattern. Anti-Ago2/Su antibodies were found in 13% (7/52), anti-Ro/SSA in 10% (5/52), anti-La in one case. The clinical profile of patients did not seem to be related to the presence of these antibody specificities. However, levels of IgG anti-β2 glycoprotein I antibodies were lower in anti-Ago2/Su positive patients (p = 0.02). None of anti-Ago2/Su or —Ro patients developed SLE during a 2-year follow-up. Ago2 is a key component of GWBs, however, only 1/7 anti-Ago2/Su serum showed a typical cytoplasmic GWBs staining.Conclusions. Anti-Ago2/Su and -Ro antibodies are the two autoantibodies detected by IP in our PAPS cohort. Clarifying why Ago2/Su and Ro are specific targets of autoimmunity may help to understand the mechanisms of autoantibody production.

Analysis of Epitope Regions for Autoantibodies in Catalase

Catalase is reported to be one of the target antigens for autoantibodies in various pathologies. To understand the mechanism of autoantibody production, we compared the several properties of autoantigenic epitopes (AE)-1 and -2 of mouse catalase, which reported to react with antibodies from sera of Helicobacter hepaticus-infected mice; AE-3 and -4 of rat catalase, which we found to be susceptible to autoimmunity; and antigenic epitope (E)-1 of H. pylori catalase, which is recognized by monoclonal antibodies produced by immunized mice. Amino acid sequences of AE-1 and -2 were similar among both mammalian and pathogenic microorganism catalases, whereas that of E-1 differed. Amino acid sequences of AE-3 and -4 were similar among mammalian catalases but differed from pathogenic microorganism catalases. Based on local relative rates of evolution, these vertebrate catalases were divided into 5 segments. E-1 included a faster evolving region, whereas AE-1 and -2 included a slowly evolving region; AE-3 and -4 comprised a slowly evolving patch within a faster evolving region. In conclusion, although AE-1 and -2 of catalase have been reported to contribute to autoimmune responses in animals infected with catalase-producing pathogens, AE-3 and -4 appear to have a different mechanism for autoantibody production.

Necrotic Cells Induce Systemic Autoimmune Disease in vivo by Activation of Dendritic Cells (DCs)

RATIONALE: The mechanism for autoantibody production in systemic lupus erythematosus remains unclear. Dying cells are likely to be a source of autoantigens. We hypothesized that DCs may take up dying cells and induce autoimmunity.METHODS: Bone-marrow-derived DCs were co-cultured with syngeneic necrotic (freezing-thawing) or apoptotic (UV-irradiated) splenocytes. After 24 co-culture, DCs capturing dying cells were injected into female 11-week-old MRL/MP-+/+ mice. Blood was taken at two-week interval and was determined by ELISA for autoantibody level. Morphological changes in kidney were examined by immunofluorescent staining and transmission electron microscopy. T-cell stimulatory capacity of DCs was determined by mixed leukocyte reaction.RESULTS: Compared with DCs with apoptotic cells, DCs phagocytosing necrotic cells induced significantly higher serum levels of anti-double-stranded DNA antibodies IgG and IgG2a, (n = 3∼5, P<0.01), and higher level of proteinuria (P<0.05). Immunofluorescent staining showed strong immune complex deposition in kidney, which was further confirmed by transmission electron microscopy. Mice receiving DCs with necrotic cells developed subsequently a ‘butterfly’ facial skin lesion similar to that observed in human lupus. Flow cytometry analysis demonstrated that necrotic cells upregulated expression of surface MHC class II, CD80, CD86 and CD40 of DCs comparably to apoptotic cells. In response to lipopolysaccharide, DCs that have captured necrotic cells significantly secreted substantial TH1 cytokine INF-g at 24, 48, 72 hours (P<0.01). DCs that have phagocytosed necrotic cells significantly increased the proliferation of C57BL/6N and MRL/+ T cells (P<0.05).CONCLUSIONS: Activation of DCs by necrotic cells might promote TH1 autoimmune responses, leading to the systemic autoimmune disease in vivo. RATIONALE: The mechanism for autoantibody production in systemic lupus erythematosus remains unclear. Dying cells are likely to be a source of autoantigens. We hypothesized that DCs may take up dying cells and induce autoimmunity. METHODS: Bone-marrow-derived DCs were co-cultured with syngeneic necrotic (freezing-thawing) or apoptotic (UV-irradiated) splenocytes. After 24 co-culture, DCs capturing dying cells were injected into female 11-week-old MRL/MP-+/+ mice. Blood was taken at two-week interval and was determined by ELISA for autoantibody level. Morphological changes in kidney were examined by immunofluorescent staining and transmission electron microscopy. T-cell stimulatory capacity of DCs was determined by mixed leukocyte reaction. RESULTS: Compared with DCs with apoptotic cells, DCs phagocytosing necrotic cells induced significantly higher serum levels of anti-double-stranded DNA antibodies IgG and IgG2a, (n = 3∼5, P<0.01), and higher level of proteinuria (P<0.05). Immunofluorescent staining showed strong immune complex deposition in kidney, which was further confirmed by transmission electron microscopy. Mice receiving DCs with necrotic cells developed subsequently a ‘butterfly’ facial skin lesion similar to that observed in human lupus. Flow cytometry analysis demonstrated that necrotic cells upregulated expression of surface MHC class II, CD80, CD86 and CD40 of DCs comparably to apoptotic cells. In response to lipopolysaccharide, DCs that have captured necrotic cells significantly secreted substantial TH1 cytokine INF-g at 24, 48, 72 hours (P<0.01). DCs that have phagocytosed necrotic cells significantly increased the proliferation of C57BL/6N and MRL/+ T cells (P<0.05). CONCLUSIONS: Activation of DCs by necrotic cells might promote TH1 autoimmune responses, leading to the systemic autoimmune disease in vivo.

Glucose-6-phosphate isomerase variants play a key role in the generation of anti-GPI antibodies: possible mechanism of autoantibody production

Glucose-6-phosphate isomerase (GPI), recognized as an autoantigen in the K/BxN arthritis model, is a ubiquitous cytoplasmic enzyme. Anti-GPI antibodies (Abs) are also detected in the serum of patients with arthritic diseases including rheumatoid arthritis (RA). So far, 24 GPI variants have been reported and most of these variants relate to non-spherocytic hemolytic disease. To understand the mechanisms of anti-GPI Ab production, cDNAs from peripheral blood mononuclear cells of subjects with or without anti-GPI Abs were cloned and sequenced. We identified 39 new GPI variants (57–1596bp). The frequency of GPI variants in healthy control subjects (HS) with anti-GPI Abs (27/73, 31.5%) was significantly higher than that in anti-GPI Ab-negative HS (5/78, 6.4%, p<0.001). The frequency of GPI variants in anti-GPI Ab-positive RA patients (22/77, 28.6%) was more significantly higher than in anti-GPI Ab-negative patients (1/63, 1.6%, p<0.0001). Our results suggest that GPI variants may play a crucial role in the production of autoantibodies against ubiquitous GPI autoantigens.

Antinuclear Autoantibodies in Flaky Skin ( fsn ) Mutant Mice

Mice homozygous for the flaky skin ( fsn ) single gene mutation have a severe hyperproliferative disease resulting complex phenotype, which includes widespread inflammation and autoimmunity. Flaky skin mice have several serological and pathological features that share similarities with the human systemic autoimmune disease systemic lupus erythematosus (SLE). Analyses of the antinuclear and anti-dsDNA autoantibodies in fsn / fsn mice indicate that they are low titer IgG antibodies. These low titer anti-dsDNA autoantibodies can ultimately form immune complex deposition in the glomeruli associated kidney damage. IgE antibodies were identified in the immune complex deposition, however their role in the pathology is not determined. It is hypothesized that the mechanism of autoantibody production and autoimmune disease pathogenesis in mice homozygous for the fsn mutation is initiated by non-specific polyclonal activation of B-lymphocytes resulting in the synthesis of low affinity autoantibodies.

Reactivity of anti-proliferating cell nuclear antigen (PCNA) murine monoclonal antibodies and human autoantibodies to the PCNA multiprotein complexes involved in cell proliferation.

Proliferating cell nuclear Ag (PCNA) occurs as a component of multiprotein complexes during cell proliferation. We found the complexes to react with murine anti-PCNA mAbs, but not with anti-PCNA Abs in lupus sera. The complexes were purified from rabbit thymus extract by affinity chromatography using anti-PCNA mAbs (TOB7, TO17, and TO30) and analyzed by ELISA, immunoprecipitation, immunoblotting, and HPLC gel filtration. That PCNA was complexed with other proteins was demonstrated by its copurification with a group of proteins excluded by an HPLC G3000 SW column. Although immunoblot analysis showed the mAbs to react exclusively with the 34-kDa PCNA polypeptide, they nonetheless immunoprecipitated the same group of proteins, confirming the interaction of the isolated PCNA with other proteins. Anti-PCNA sera, including AK, which reacts with biologically functional sites on PCNA, did not react with complexed PCNA, but did react with it once it was dissociated from the complexes. PCNA complexes in turn reacted with murine anti-DNA mAbs, as well as with Abs against p21, replication protein A, DNA helicase II, cyclin-dependent kinases 4 and 5, and topoisomerase I. These findings suggest that the PCNA complexes purified using anti-PCNA mAbs comprise the "protein machinery" for DNA replication and cell cycle regulation. They also suggest that anti-PCNA mAbs are useful tools with which to characterize the protein-protein interactions within PCNA complexes, as well as the autoimmune responses to proteins interacting with PCNA, which may shed light on the mechanisms of autoantibody production in lupus patients.

IFN-gamma transgenic mice: clues to the pathogenesis of systemic lupus erythematosus?

Transgenic mice overexpressing IFN-γ in the epidermis develop an inflammatory skin disease resembling cutaneous lupus erythematosus shortly after birth. By 3 months of age, most female transgenics develop a lupus-like syndrome characterised by production of IgG anti-dsDNA, antihistone and antinucleosome autoantibodies. The autoantibodies are nephritogenic, with one-third of females developing a severe immune complex mediated glomerulonephritis. Analysis of these transgenics suggests that pathogenic autoantibodies arise via an antigen-driven T-cell-dependent mechanism with apoptotic keratinocytes acting as a potential source of autoantigen. The mechanism of autoantibody production in IFN-γ transgenics may be relevant to human lupus and is consistent with a central role for cutaneous T cells in the pathogenesis of systemic lupus erythematosus in man.

The mechanism of autoantibody production in an autoimmune MRL/lpr mouse.

Rheumatoid factors (RF) and anti-DNA Abs from MRL/lpr mice have features similar to Abs directed toward foreign Ags, indicating a role of specific activation by Ags during disease. But our previous studies and analogous studies from others concentrated on a limited subset of hybridomas selected on the basis of Ag binding to well characterized target autoantigens. Thus, it has been unclear to what extent clonal expansion is restricted to identifiable autospecificities. To obtain a more complete picture of disease-associated autoantibody production, we designed the following experiment. A large number of B cell hybridomas were generated from the spleen of an MRL/lpr mouse and then analyzed for self-specificity, sequence, and clonal relationship. Surprisingly, we found that clonal expansion was limited to only a few autospecificities, implying a unique property of this response. In addition, we used Southern blotting with heavy and L chain constant region probes to screen both RF and non-RF hybridomas for membership in clones, one of which was first identified among RF hybridomas. We found no non-RF members of this clone. The size and number of mutations of this clone were sufficient for us to conclude that nonspecific (i.e., non-RF) mutant members are rapidly lost. Had an Ag other than IgG2a been driving clonal expansion, we should have seen mutants that retained spectificity for that Ag but that lost specificity for IgG2a. This observation, along with the restriction of clonal expansion to a few autospecificities, provides strong evidence that normal autoantigens themselves drive autoantibody clonal expansion.

Identification of Commonly Recognized Epitopes on a Rare Autoantigen: Poly(ADP-ribose) Polymerase

To analyze mechanisms of autoantibody production, epitope mapping of a rare autoantigen, poly(ADP-ribose) polymerase, was performed. A cDNA fragment (1873 bp long), which was already confirmed to encode the autoepitopes of this protein, was subcloned into a protein expression plasmid pEX. Several deletion mutants were produced by enzymatic treatments of this construct. PCR-amplified cDNA fragments were also individually subcloned into this vector. The recombinant proteins produced in Escherichia coli by these vectors were tested for their respective antigenicities by immunoblotting. It was found that all positive sera tested (seven cases) strongly recognized common epitopes in a restricted region of the molecule. Furthermore, three out of the seven positive sera were found to recognize other parts of the molecule. The data suggest possible mechanisms for the formation of anti-poly(ADP-ribose) polymerase autoantibodies.

Autoimmunity against Thyroid Hormones

The presence of thyroid hormone autoantibodies (THAA) is a common phenomenon. More than 270 cases have been reported by the end of 1993 involving not only thyroidal but also nonthyroidal disorders. Clinically, THAA in a patient's serum produces variation in thyroid hormone metabolism and, in particular, may interfere with the radioimmunoassay (RIA) results of total or free thyroid hormone measurements, which can cause unusually high or low values of the hormones depending on the B/F separation method used. This in vitro interference can give clinicians confusing information about the patient's thyroid state. As a result, the patient may receive inappropriate treatment from physicians who are unaware of this disorder. The presence of THAA has been reported not only in humans but also in dogs, chickens, and rats. In this review article, clinical features of THAA and the mechanism of autoantibody production are discussed.

Human monoclonal antibodies from a patient with primary biliary cirrhosis that recognize two distinct autoepitopes in the E2 component of the pyruvate dehydrogenase complex

Peripheral B lymphocytes from a patient with primary biliary cirrhosis were infected with Epstein-Barr virus, and Epstein-Barr virus-transformed B lymphocytes producing large amounts of IgG antibodies to pyruvate dehydrogenase complex were selected, expanded and fused with the human-mouse heteromyeloma cell line F3B6. The resulting Epstein-Barr virus-transformed B-cell hybrids were repeatedly cloned by limiting dilution, and three stable hybridoma clones producing human monoclonal antibodies to pyruvate dehydrogenase complex were generated. These monoclonal antibodies, designated M18GP8, M37GP11 and M82GP8, specifically bound to pyruvate dehydrogenase complex, and their dissociation constant with pyruvate dehydrogenase complex was calculated to be 2.4 x 10(-11), 2.3 x 10(-10) and 2.6 x 10(-11) mol/L, respectively. These three monoclonal antibodies stained the mouse stomach/kidney cryostat sections in a typical immunofluorescence pattern of antimitochondrial antibody. Furthermore, the enzymatic activity of pyruvate dehydrogenase complex was almost completely inhibited by the three monoclonal antibodies. Western blotting analysis revealed that M18GP8 and M82GP8 reacted with only pyruvate dehydrogenase complex-E2 in contrast to M37GP11, which reacted with both pyruvate dehydrogenase complex-E2 and protein X. The binding of monoclonal antibody M37GP11 to solid-phase pyruvate dehydrogenase complex was partially inhibited by two different synthetic peptides corresponding to both the inner and outer lipoyl-binding domains of pyruvate dehydrogenase complex-E2. These monoclonal antibodies, which are the first human monoclonal antibodies to pyruvate dehydrogenase complex generated from a patient with primary biliary cirrhosis, will be a valuable tool for studying the B-cell autoepitopes in PDC and the mechanism of autoantibody production in primary biliary cirrhosis.

Human monoclonal antibodies from a patient with primary biliary cirrhosis that recognize two distinct autoepitopes in the E2 component of the pyruvate dehydrogenase complex

Peripheral B lymphocytes from a patient with primary biliary cirrhosis were infected with Epstein-Barr virus, and Epstein-Barr virus–transformed B lymphocytes producing large amounts of IgG antibodies to pyruvate dehydrogenase complex were selected, expanded and fused with the human-mouse heteromyeloma cell line F3B6. The resulting Epstein-Barr virus–transformed B-cell hybrids were repeatedly cloned by limiting dilution, and three stable hybridoma clones producing human monoclonal antibodies to pyruvate dehydrogenase complex were generated. These monoclonal antibodies, designated M18GP8, M37GP11 and M82GP8, specifically bound to pyruvate dehydrogenase complex, and their dissociation constant with pyruvate dehydrogenase complex was calculated to be 2.4 × 10−11, 2.3 × 10−10 and 2.6 × 10−11 mol/L, respectively. These three monoclonal antibodies stained the mouse stomach/kidney cryostat sections in a typical immunofluorescence pattern of antimitochondrial antibody. Furthermore, the enzymatic activity of pyruvate dehydrogenase complex was almost completely inhibited by the three monoclonal antibodies. Western blotting analysis revealed that M18GP8 and M82GP8 reacted with only pyruvate dehydrogenase complex-E2 in contrast to M37GP11, which reacted with both pyruvate dehydrogenase complex-E2 and protein X. The binding of monoclonal antibody M37GP11 to solid-phase pyruvate dehydrogenase complex was partially inhibited by two different synthetic peptides corresponding to both the inner and outer lipoyl-binding domains of pyruvate dehydrogenase complex-E2. These monoclonal antibodies, which are the first human monoclonal antibodies to pyruvate dehydrogenase complex generated from a patient with primary biliary cirrhosis, will be a valuable tool for studying the B-cell autoepitopes in PDC and the mechanism of autoantibody production in primary biliary cirrhosis. (HEPATOLOGY 1993;18:1069-1077).

B cell epitope on the U1 snRNP‐C autoantigen contains a sequence similar to that of the herpes simplex virus protein

The mechanism of autoantibody production in autoimmune diseases is not well understood. In the present study we performed the B cell epitope mapping of the U1 small nuclear ribonucleoprotein (snRNP)-C, one of the target molecules of anti-nRNP autoantibody to investigate how B cells respond to the autoantigen. After cloning and expression of a full length complementary DNA (cDNA) encoding the U1-C protein, several truncated mutants of the cDNA were constructed and expressed in E. coli. Although a few epitopes were distributed on the whole molecule, all anti-C protein antibody-positive patients' sera tested recognized the region between amino acid residues 102 and 125 of the coding sequence. This universal epitope region contains an amino acid sequence similar to that of the herpes simplex virus type 1 ICP4 protein. The peptides representing each molecule were cross-reactive to each other. In addition this region cross-reacted to the B/B' protein. These observations suggest that molecular mimicry might be involved in the initiation of autoantibody production, followed by cross-reactive events between the autoantigens and by antigen-driven mechanisms to generate more complicated autoantibody patterns against the U1 snRNP complexes.

Differential effects of prednisone and cyclophosphamide on autoantibodies in human neuromuscular disorders

We compared the effects of treatment of patients with prednisone or cyclophosphamide on a series of different types of autoantibodies. Levels of antiacetylcholine receptor (anti-AChR) antibodies and of antibodies to GM1 and GD1a gangliosides were measured in patients with a variety of neuromuscular disorders before and after treatment. Most patients had several autoantibodies present. We showed that prednisone treatment resulted in a reduction in titers of anti-AChR but not antiganglioside antibodies. Cyclophosphamide treatment produced a reduction of antiganglioside antibody titers. An intravenous and oral regimen was more effective than a single intravenous course of cyclophosphamide. We conclude that an immunosuppressive medication such as prednisone may reduce levels of some autoantibodies while producing no change in others, even in an individual patient. In addition, cyclophosphamide can suppress autoantibodies that prednisone does not. These differences in immunopharmacologic responses suggest that there are several distinct mechanisms of autoantibody production in humans. The utility of immunosuppressive medications in specific disease processes may be related in part to the mechanism of production of pathogenic antibodies.

Mononuclear Cell Infiltrates in Bullous Disease

Mononuclear cell subset-specific monoclonal antibodies, indirect immunoperoxidase labeling, and a specific quantification technique were used to determine the constitution of mononuclear cell infiltrates associated with bullous pemphigoid (BP), pemphigus vulgaris (PV), dermatitis herpetiformis (DH), and linear IgA bullous disease, as well as those in normal skin (NS) from healthy adult volunteers. Bullous pemphigoid and PV lesions contain significantly greater numbers of T lymphocytes (p less than 0.001), including both T helper/inducer and T cytotoxic/suppressor subsets, macrophages (p less than 0.002), and Langerhans cells (p less than 0.01), than NS or lesions of DH, supporting the concept that cell-mediated immunity is involved in bulla formation and autoantigen presentation in BP and PV. The infiltrates associated with DH lesions appear to reflect a different mechanism of autoantibody production and bulla formation.

Mechanisms of autoantibody production in autoimmune MRL mice.

The quantitative expression of anti-DNA and anti-Sm antibodies has been investigated in autoimmune MRL-lpr/lpr and MRL-+/+ mice. Anti-Sm antibodies were detected in sera from 21/23 lpr/lpr and 10/16 +/+ mice, with individual animals showing striking variation in the time-course and magnitude of this autoantibody response. The peak antibody levels of the responding animals of each substrain did not differ significantly. For anti-DNA antibody, a different pattern of responsiveness was observed. Individual animals of each substrain produced very similar responses in terms of the magnitude and time-course of serum anti-DNA antibody. The differences in the peak levels of the two substrains were highly significant, with lpr/lpr mice demonstrating a much greater anti-DNA antibody response than +/+ mice. In lpr/lpr mice tested for both autoantibody systems, serum anti-DNA and anti-Sm antibodies showed distinct time-courses. These studies indicate that anti-DNA and anti-Sm antibodies are expressed independently in MRL mice, with the expression of anti-DNA, but not anti-Sm antibody markedly influenced by the presence of the 1pr gene. A fundamental difference in the mechanisms involved in the generation of anti-DNA and anti-Sm antibodies is suggested by the quantitative pattern of the two responses.