Testis-expressed protein TSGA10 an auto-antigen in autoimmune polyendocrine syndrome type I

Autoimmune polyendocrine syndrome type 1 (APS1) is a rare monogenic autosomal recessive disorder. Autoimmune gonadal failure is often one of its features. The aim of this study was to identify targets of immune reactions associated with male autoimmune hypogonadism in APS1. Human testis cDNA expression library immunoscreening with APS1 patients' sera identified the protein testis-specific protein 10 (TSGA10), which is a testis-expressed protein with a key role in spermatogenesis. The corresponding serum autoantibodies were detected by Radioimmunoprecipitation assay in 3 of 40 male (7.5%) and 2 of 26 female (7.7%) APS1 patients but in none of either 32 patients with Addison's disease or 116 healthy controls (p = 0.0055). However, the TSGA10 antibodies in APS1 patients showed no correlation with testicular or ovarian failure or with autoimmune hypogonadism markers. Nevertheless, their presence in a proportion of patients with APS1 highlights the role of TSGA10 as a target of immune reactions in APS1.     

Novel neuronal and endocrine autoantibody targets in autoimmune polyendocrine syndrome type 1

Context. Although pituitary autoantibodies have frequently been reported in Autoimmune Polyendocrine Syndrome type 1 (APS1), the autoimmune involvement of the hypothalamic-pituitary axis remains to be elucidated. Objective. Our aim was to identify in APS1 patients novel autoantibodies, especially against hypothalamic-pituitary targets, and to correlate their presence with clinical features. Patients. We analyzed 14 APS1 patients from Sardinia, compared to other diseases and healthy donors. Measure(s). We used immunohistochemistry, on tissues substrates from various neuroendocrine organs, to detect autoantibody targets. Immunoenzymatic assays, as well as absorption with specific antigens were used to reveal autoantibodies against growth hormone (GH), luteinizing hormone (LH) and somatocrinin (GHRH). Clinical evaluations included GH secretory and cardiovascular autonomic neuropathy tests. Results. Sera from 12/14 APS1 patients revealed autoantibodies reacting with the hypothalamic-pituitary axis, cerebellum, substantia nigra, and/or adrenal medulla, as well as with GH, LH and/or GHRH. Of APS1 patients, 5 showed GH deficiency, in association (4/5 cases) with autoantibodies to hypothalamic and/or pituitary targets. Hypogonadotrophic hypogonadism was revealed in one APS1 patient, together with autoantibodies against gonadotropes. Autonomic neuropathy was detected in 5 of 10 patients, associated with autoantibodies to adrenal medulla in 2 cases. Of 5 patients with autoantibodies to cerebellar neurons, 2 reported emotional or memory alterations. Conclusions. The majority of Sardinian APS1 patients developed autoantibodies to an assortment of neuroendocrine cells. Novel targets of clinical relevance may include pituitary hormones, uncharacterized pituitary targets, and adrenal medullary cells. An high prevalence of GH deficiency, and possibly of autonomic neuropathy, were also revealed.     

Antiribonuclease H2 antibodies are an immune biomarker for systemic lupus erythematosus

We previously reported that autoantibodies against the proliferating cell nuclear antigen protein (PCNA)-binding protein chromatin assembly factor-1 (CAF-1) are specifically found in patients with systemic lupus erythematosus (SLE). PCNA and its complex constituents elicit autoimmune responses in patients with SLE, suggesting that autoantibody diversification likely occurs owing to epitope spreading. Therefore, we sought to clarify whether patients with SLE exhibit an autoimmune response to Ribonuclease H2 (RNase H2), another PCNA-binding protein that regulates cell division. As results, RNase H2 autoantibodies were detected in the sera of 33.9% (19/56) of SLE patients, which was significantly higher than that observed in sera from other patients with systemic autoimmune diseases (polymyositis/dermatomyositis, systemic sclerosis, Sjogren’s syndrome, mixed connective tissue disease and rheumatoid arthritis) and healthy controls. Regression analysis also showed that serum anti-RNase H2 levels were strongly correlated to that of CAF-1 in SLE patients. Our data support the use of RNase H2 autoantibodies as a serum biomarker for SLE diagnosis. Moreover, the strong correlation observed between RNase H2 and CAF-1 suggests that intermolecular epitope spreading may play a critical role in autoantibody production and diversification in SLE.     

Identification of endothelin-converting enzyme-2 as an autoantigen in autoimmune polyendocrine syndrome type 1

Autoimmune polyendocrine syndrome type 1 (APS1) is a rare monogenic autoimmune disorder caused by mutations in the autoimmune regulator (AIRE) gene. High titer autoantibodies are a characteristic feature of APS1 and are often associated with particular disease manifestations. Pituitary deficits are reported in up to 7% of all APS1 patients, with immunoreactivity to pituitary tissue frequently reported. We aimed to isolate and identify specific pituitary autoantigens in patients with APS1. Immunoscreening of a pituitary cDNA expression library identified endothelin-converting enzyme (ECE)-2 as a potential candidate autoantigen. Immunoreactivity against ECE-2 was detected in 46% APS1 patient sera, with no immunoreactivity detectable in patients with other autoimmune disorders or healthy controls. Quantitative-PCR showed ECE-2 mRNA to be most abundantly expressed in the pancreas with high levels also in the pituitary and brain. In the pancreas ECE-2 was co-expressed with insulin or somatostatin, but not glucagon and was widely expressed in GH producing cells in the guinea pig pituitary. The correlation between immunoreactivity against ECE-2 and the major recognized clinical phenotypes of APS1 including hypopituitarism was not apparent. Our results identify ECE-2 as a specific autoantigen in APS1 with a restricted neuroendocrine distribution.     

The homogeneous multiplexed system--a new method for autoantibody profile in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a multi-systemic autoimmune disease leading to immunological aberrations and excessive multiple autoantibody production. The aim of this study was to investigate the prevalence of multiple autoantibodies in SLE patients utilizing the multiplex system method. We analyzed the presence of elevated titers of anti-Ro, anti-La, anti-RNP, anti-Sm, anti-Jo1, anti-centromere, anti-Scl-70, anti-histone, and anti-dsDNA antibodies in 199 serum samples (113 SLE patients, 86 healthy donors). We compared the type, level and number of autoantibodies and the correlation between the autoantibody profile and disease severity utilizing the SLEDAI score. Elevated titers of at least one autoantibody were detected in 48% of 42 SLE patients. Elevated titers of anti-Ro antibodies were most commonly detected. The distribution of specific autoantibodies was: anti-Ro- 23.8%, anti-dsDNA- 19%, antihistone- 19%, anti-RNP- 14.2%, anti-La antibodies- 11.9%, anti-Sm- 7.1%, anti-Scl 70-4.7%, and anti-centromere- 2.4%. Utilizing ROC analysis, the sensitivity and specificity of anti-DNA antibodies at a cutoff value of 34 IU/ml were 87.1% and 79.4% respectively. Elevated titers of anti-Jo1 antibody were not detected. There was a correlation with the titer of anti-Ro antibodies and disease activity by the SLEDAI score. Seven patients harbored one autoantibody only, 15 patients harbored 2-3 autoantibodies, 3 patients harbored 4-5 autoantibodies, and one patient harbored 6 autoantibodies. A correlation between the number of autoantibodies per patient and disease severity was found. One patient with a multitude of autoantibodies had severe lupus and a myriad of clinical manifestations. In conclusion, the multiplex system is specific and sensitive, provides an autoantibody profile in a single test, and may be useful as a diagnostic test for SLE. Elevated anti-Ro antibodies are associated with severe disease. An autoantibody load may be indicative of more severe disease.     

Onset and regulation of anti-lamin B autoantibody production is independent of the level of polyclonal activation

Anti-lamin B autoantibodies are associated with both systemic lupus erythematosus (SLE) and autoimmune liver disease. We examined the possibility that the underlying clinical feature in patients with anti-lamin B autoantibodies might be chronic autoimmune liver disease, and whether the hypergammaglobulinemia present in both disorders is involved in generating anti-lamin B autoantibodies. A lamin B fusion protein (MLB1), consisting of amino acids 77-533 of lamin B fused to TrpE, was used to screen sera from 84 patients with SLE for anti-lamin B autoantibodies. 3/4 prototype human lamin B antisera, 5/84 SLE sera (6%), and 0/30 sera from healthy individuals reacted with MLB1 on immunoblots at a 1:500 dilution. Of the 9 anti-lamin B autoantibody positive patients studied, all but 1 fulfilled at least four ARA criteria for SLE. None of the patients displayed evidence of chronic autoimmune liver disease, suggesting that autoimmune liver disease is not strongly associated with anti-lamin B antibodies in SLE. In SLE, as in "lupoid hepatitis", anti-lamin B autoantibodies are often produced transiently during periods of increased disease activity. Although polyclonal hypergammaglobulinemia is also associated with increased activity of both diseases, anti-lamin B autoantibody production in 2 patients was independent of total immunoglobulin levels, antibodies to irrelevant proteins, and production of some other autoantibodies. Thus, polyclonal activation is insufficient to explain either the initiation or regulation of anti-lamin B autoantibody production, supporting the hypothesis that antinuclear antibodies are antigen-selective.     

Characterization of ribosomal P autoantibodies in relation to cell destruction and autoimmune disease

Autoantibodies against the ribosomal P proteins are related to cell death and tissue destruction and are frequently exhibited in patients with systemic lupus erythematosus (SLE). In an attempt to explore the effect of tissue destruction on the induction of anti-P autoantibodies, we searched for anti-P autoantibodies by enzyme-linked immunosorbent assay in 201 antinuclear antibody (ANA)-positive individuals, in 10 patients with treated kidney SLE and in 45 acute leukaemia patients undergoing intensive chemotherapy. The autoantibody reactivity was further characterized using one- and two-dimensional immunoblot analysis and immunofluorescence. Anti-P were detected in 5.5% (11/201) of ANA-positive individuals, but not in kidney-affected SLE patients or in patients with leukaemia. Seven of 11 anti-P-positive patients had SLE (3/11), primary Sj?grens's syndrome (1/11) and other autoimmune diseases (3/11). A relation between disease activity and anti-P was suggested by follow-up examinations in one SLE patient, supported by the absence of anti-P autoantibodies in the 10 treated kidney SLE patients. Anti-P autoantibodies were detected by immunoblot in one patient with SLE indicating anti-P2 predominance and in the patient with Sj?grens's syndrome indicating anti-P1 predominance. Diverging humoral responses in these ANA- and anti-P-positive patients were further illustrated by immunofluorescence, elucidating varying nuclear reactivity and anti-P pattern. The observation of anti-P in individuals with active autoimmune disease, but not in patients with chemotherapy-induced cell damage, suggests that anti-P antibodies are part of a specific disease process, and not elicited as a response to cell destruction per se.     

Anti-phospholipid antibodies in HIV infection and SLE with or without anti-phospholipid syndrome: comparisons of phospholipid specificity, avidity and reactivity with beta2-GPI.

Increased prevalence of anti-phospholipid antibodies (aPL) and increased levels of lipid peroxidation have been described in patients with HIV infection. To assess the binding specificity and avidity of aPL antibodies in HIV infection, sera from 44 HIV-1 infected patients were evaluated for antibodies to cardiolipin (aCL), phosphatidyl serine (aPS), phosphatidyl inositol (aPI) and phosphatidyl choline (aPC) using enzyme linked immunosorbent assay (ELISA) methods. Sera from 30 patients with systemic lupus erythematosus (SLE), but without features of anti-phospholipid syndrome (APS) (SLE/non APS), six with SLE and secondary APS, (SLE/APS) and 11 with primary APS (PAPS) were also evaluated as controls. The resistance of the aPL antibody binding to dissociating agents was evaluated by treating the ELISA wells, after serum incubation with 2 M urea or 0.6 M NaCl for 10 min. An anti-beta2-glycoprotein-I (beta2-GPI) ELISA was used to assess serum reactivity against beta2-GPI, a plasma protein considered as the true antigen of aCL antibodies occurring in APS and SLE patients. The prevalence of aCL, aPS, aPI and aPC antibodies in HIV-1 infection was 36%, 56%, 34% and 43% respectively, which was comparable to that found in SLE/APS and PAPS patients and significantly higher than that observed in SLE/non-APS patients. Anti-beta2-GPI antibodies occurred in 5% of HIV-1 infected vs. 17% in SLE/non-APS (P=0.11), 50% in SLE/APS (P=0.009) and 70% in PAPS patients (P=0.0014). A significant decrease of aPL binding after urea and NaCl treatment was observed in the sera of HIV-1-infected, compared to that of APS patients, indicating that aPL antibodies from HIV-1 infected individuals have low resistance to dissociating agents. In conclusion, aPL antibodies (1) occur in HIV-1 infection; (2) tend to recognize various phospholipids but not beta2-GPI; and (3) are of low resistance to dissociating agents-a finding probably reflecting low antibody avidity. Finally, these, like the autoimmune-type aCL antibodies, tend to recognize the oxidized CL-a finding probably indicating autoantibody generation as a result of neoepitope formation by oxidized PLs.     

Presence of autoantibodies to apolipoprotein A-1 in patients with acute coronary syndrome further links autoimmunity to cardiovascular disease

Anti-apolipoprotein A-1 (Apo A-1) autoantibodies were described in autoimmune disorders such as systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS) and might be involved in the genesis of arterial and venous thrombotic events. To investigate the presence of these autoantibodies in patients with acute coronary syndrome (ACS) without other features of autoimmunity, we set up an enzyme-linked immunosorbent assay (ELISA) for anti-Apo A-1 antibodies. We used it to investigate their prevalence in ACS as compared to SLE and APS and correlated them to plasma Apo A-1 and serum amyloid A protein (SAA) concentrations. The prevalence of anti-Apo A-1 autoantibodies in the healthy control group was 1% (1/92), but was significantly higher in other groups: 21% (11/53) in ACS group (P=0.001), 13% (12/92) in SLE and/or APS group (P=0.005). Multiple linear regression revealed a significant correlation between plasma Apo A-1 (r=-0.72, P=0.013), plasma SAA concentration (r=0.76, P=0.0066) and anti-Apo A-1 IgG titre in ACS patients. The presence of anti-Apo A-1 autoantibodies in patients with ACS highlights an additional link between autoimmunity, inflammation and atherosclerosis.     

Intramolecular epitope spreading among anti-caspase-8 autoantibodies in patients with silicosis,systemic sclerosis and systemic lupus erythematosus,as well as in healthy individuals

Dysregulation of apoptosis through the Fas-Fas ligand pathway is relevant in autoimmune disease onset. We recently reported elevated serum levels of sFas in patients with silicosis, systemic sclerosis (SSC) and systemic lupus erythematosus (SLE), and proposed a block of apoptosis in the pathogenesis. The disturbance of apoptosis in lymphocytes including autoreactive clones could induce autoantibody production. Since autoantibodies directed against unknown antigens are present in the sera of these patients, the sera samples were examined for the presence of autoantibodies directed to caspase-8. Using Western blotting, autoantibodies against caspase-8 were detected in healthy individuals and in over 60% of patients. Using epitope mapping employing 12 amino acid polypeptides with SPOTs system, a minimum of 4 epitopes and a maximum of 13 were found, which implied that epitope spreading was in progress. It is noteworthy that two important catalytic cystein residues were included within the epitopes; firstly the active site cystein Cys287, and secondly Cys360 located in the unique pentapeptide motif QACQG. Using recombinant human caspase-8 linked protein chip array, autoantibodies were identified and molecular weight determined. The antibodies were mainly IgG; 80% were subclass IgG1(lambda); 20% were IgG4(kappa). Despite the ratio of human light chain kappa:lambda = 2:1, the predominance of IgG1(lambda) is noticeable. Anti-caspase-8 autoantibodies are detectable in healthy individuals and in patients suffering silicosis, SSc or SLE. A few epitopes were detected in healthy individuals compared to those suffering autoimmune diseases, indicating the intramolecular epitope spreading. Relationship of autoantibodies and the clinical background of the patients requires clarification.     

Autoantibodies associated with primary biliary cholangitis are common among patients with systemic lupus erythematosus even in the absence of elevated liver enzymes

Knowledge of concomitant autoimmune liver diseases (AILD) is more detailed in primary Sjögren’s syndrome (pSS) compared to systemic lupus erythematosus (SLE). Herein, the prevalence of autoantibodies associated with autoimmune hepatitis (AIH) and primary biliary cholangitis (PBC) was investigated in stored sera from patients with SLE (n = 280) and pSS (n = 114). Antibodies against mitochondria (AMA), liver–kidney microsomal (LKM) antigen, smooth muscle (SMA) and anti‐nuclear antibodies (ANA) were analysed with immunofluorescence microscopy. In addition, AILD‐associated autoantibodies were tested with immunoblot. Prior to sampling, eight SLE (2·9%) and three pSS (2·6%) cases were diagnosed with AILD. Among SLE‐cases without known AILD (n = 272), 26 (9·6%) had PBC‐associated autoantibodies, 15 (5·5%) AIH‐associated autoantibodies (excluding ANA) and one serological overlap. Most subjects with PBC‐associated autoantibodies had liver enzymes within reference limits (22 of 27, 81%) or mild laboratory cholestasis (two of 27, 7·4%), while one fulfilled the diagnostic PBC‐criteria. AMA‐M2 detected by immunoblot was the most common PBC‐associated autoantibody in SLE (20 of 272, 7·4%). The prevalence of SMA (4·4%) was comparable with a healthy reference population, but associated with elevated liver enzymes in four of 12 (25%), none meeting AIH‐criteria. The patient with combined AIH/PBC‐serology had liver enzymes within reference limits. Among pSS cases without known AILD (n = 111), nine (8·1%) had PBC‐associated, 12 (10·8%) AIH‐associated autoantibodies and two overlapped. PBC‐associated autoantibodies were found as frequently in SLE as in pSS but were, with few exceptions, not associated with laboratory signs of liver disease. Overall, AILD‐associated autoantibodies were predominantly detected by immunoblot and no significant difference in liver enzymes was found between AILD autoantibody‐negative and ‐positive patients.     

IgG autoantibodies against beta2-glycoprotein I complexed with a lipid ligand derived from oxidized low-density lipoprotein are associated with arterial thrombosis in antiphospholipid syndrome

We recently reported [J. Lipid Res. 42 (2001), 697; 43 (2002), 1486; 44 (2003), 716] that [beta2-glycoprotein I (beta2GPI) forms complexes with oxidized LDL (oxLDL) and autoantibodies against these complexes are present in patients with SLE and antiphospholipid syndrome (APS). The relationship of beta2GPI/oxLDL complexes and IgG autoantibodies against beta2GPI complexed with oxLig-1 (an oxLDL-derived ligand) with clinical manifestations of APS was studied in 150 APS and SLE patients. The beta2GPI/oxLDL levels of APS patients were similar to those of SLE patients without APS, but they were significantly higher than healthy individuals. There was no difference in the complex levels among the patients with arterial, venous thrombosis, or pregnancy morbidity. IgG anti-beta2GPI/oxLig-1 levels of APS were significantly higher than those of SLE without APS and healthy individuals. Further, antibody levels of APS patients with arterial thrombosis were significantly higher than those patients with venous thrombosis and pregnancy morbidity. Thus, oxidation of LDL leads the complex formation with beta2GPI in SLE and APS patients. In contrast, anti-beta2GPI/oxLig-1 autoantibodies were generated only in APS and were strongly associated with arterial thrombosis. These results suggest that autoantibodies against beta2GPI/oxLDL complexes are etiologically important in the development of atherosclerosis in APS.     

Detection, epitope-mapping and function of anti-Fas autoantibody in patients with silicosis

Dysregulation of apoptosis through the Fas-Fas ligand pathway is associated with the onset of autoimmune disease. Since autoantibodies directed against unknown antigens are present in the sera of these patients, sera samples were examined for the presence of autoantibodies directed against the Fas molecule. Using Western blotting and a ProteinChip analysis, autoantibodies against Fas were detected in patients with silicosis, systemic lupus erythematosus (SLE) and systemic sclerosis (SSc), and weakly detected in healthy individuals. Using epitope mapping employing 12-amino-acid polypeptides with the SPOTs system, a minimum of four epitopes and a maximum of 10 epitopes were found. Several amino acid residues involved in binding FasL, such as C66, R87, L90, E93 and H126, were presented within the epitopes. Serum containing a large amount of anti-Fas autoantibody from silicosis patients inhibited the growth of a Fas-expressing human cell line, but did not inhibit the growth of a low Fas-expresser nor a Fas-expresser in which the Fas gene had been silenced by small interference RNA. All epitopes in the intracellular region of Fas were located in the death domain. The possible roles of anti-Fas autoantibody detected in healthy volunteers and patients with silicosis or autoimmune diseases are discussed here.     

p53 autoantibodies in patients with autoimmune diseases: a quantitative approach

With few exceptions, autoantibodies directed against the gene product of the tumor suppressor gene p53 are only detected in cancer patients. From 73 patients with various autoimmune diseases, we obtained 17 sera with elevated autoantibodies against the p53 protein comprising patients with SLE, Graves' disease, and immune vasculitis including Wegener's granulomatosis. The overall prevalence (23%) of p53 autoantibodies was comparable to that in various cancers; differences, however, were obvious with respect to the magnitude of antibody levels. Only 5% of seropositive colorectal cancer patients had levels within the critical range (150-180 U/ml) but nearly half (41%) of seropositive autoimmune disease patients were that low. None of the autoimmune disease patients exceeded 300 U/ml serum compared to more than 60% of seropositive colorectal cancer patients with higher levels. This remarkable difference in magnitude underlines the necessity of quantification of p53 autoantibodies over a mere qualitative determination. Patients with autoimmune diseases face an increased risk for malignancies. It still remains to be established whether p53 seropositivity in autoimmune diseases adds to the rare exceptions of p53AAb in non-malignant diseases or is indicative for a yet occult cancer.     

Presence of autoantibodies to peptidyl-prolyl cis-trans isomerase (cyclosporin A-binding protein) in systemic lupus erythematosus.

Several autoantibodies against cytoplasmic or nuclear components of cells have been reported in autoimmune diseases. We report here a previously unrecognized autoantibody to peptidyl-prolyl cis-trans isomerase (PPIase) in patients with systemic lupus erythematosus (SLE). PPIase, which catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides, has recently been found to be identical to cyclophilin, a specific binding protein of a potent immunosuppressant, cyclosporin A. IgG and IgM anti-PPIase antibodies were detected in 40 and 20% of unselected patients with SLE, respectively, by ELISA. The reactivity of these sera was confirmed by immunoblotting experiments. Sera from rheumatoid arthritis patients showed no reactivity and 1 of 8 sera from systemic sclerosis patients and 1 of 25 sera from normal controls showed only weak reactivity. Unexpectedly, the anti-PPIase antibody was unable to inhibit PPIase activity, indicating that the autoantibody recognizes an epitope of PPIase which is different from the active site of PPIase. The levels of the anti-PPIase antibody in SLE patients correlated with remissions and flares of the disease. The anti-PPIase antibody was higher in patients with active SLE than those with inactive disease. The prevalence of the active stage of the disease was significantly higher in IgG anti-PPIase antibody-positive SLE patients as compared to antibody-negative SLE patients. These data define the presence of a new autoantibody against PPIase and its association with the activity and certain clinical manifestations in SLE.     

Anti-β 2 -Glycoprotein I Autoantibodies and Atherosclerosis

β-Glycoprotein I (β 2 -GPI) is a major antigen for antiphospholipid antibodies (aPL) present in patients with antiphospholipid syndrome (APS). We previously reported that β 2 -GPI specifically binds to oxidized low-density lipoprotein (oxLDL). Further, a ligand specific for β 2 -GPI, oxLig-1, purified from the extracted lipids of oxLDL was identified as 7-ketocholesterol-9-carboxynonanoate (i.e., 9-oxo-9-(7-ketocholest-5-en-3β-yloxy) nonanoic acid) OxLig-1 was recognized by β 2 -GPI and subsequently by anti-&beta 2 -GPI autoantibodies. Binding of liposomes containing oxLig-1 to macrophages were significantly enhanced in the presence of both β 2 -GPI and an anti-β 2 -GPI autoantibody derived from (NZW×BXSB) F1 mouse, an animal APS model, or from APS patients. Anti-β 2 -GPI autoantibodies derived from APS patients with episodes of arterial thrombosis were detected in ELISA, using a solid phase &beta 2 -GPI complex with oxLig-1. It was also reported that LDL-receptor-deficient mice that were fed a chow diet and immunized with β 2 -GPI had an accelerated atherosclerosis and that β 2 -GPI was abundantly expressed within subendothelial regions and intimal-medial borders of human atherosclerotic plaques. All of these observations strongly suggest that autoimmune atherogenesis linked to β 2 -GPI interaction with oxLDL and autoantibodies may be present in APS.     

Anti-beta 2-glycoprotein I autoantibodies and atherosclerosis

beta 2-Glycoprotein I (beta 2-GPI) is a major antigen for antiphospholipid antibodies (aPL) present in patients with antiphospholipid syndrome (APS). We previously reported that beta 2-GPI specifically binds to oxidized low-density lipoprotein (oxLDL). Further, a ligand specific for beta 2-GPI, oxLig-1, purified from the extracted lipids of oxLDL was identified as 7-ketocholesterol-9-carboxynonanoate (i.e., 9-oxo-9-(7-ketocholest-5-en-3 beta-yloxy) nonanoic acid) OxLig-1 was recognized by beta 2-GPI and subsequently by anti-beta 2-GPI autoantibodies. Binding of liposomes containing oxLig-1 to macrophages were significantly enhanced in the presence of both beta 2-GPI and an anti-beta 2-GPI autoantibody derived from (NZW x BXSB) F1 mouse, an animal APS model, or from APS patients. Anti-beta 2-GPI autoantibodies derived from APS patients with episodes of arterial thrombosis were detected in ELISA, using a solid phase beta 2-GPI complex with oxLig-1. It was also reported that LDL-receptor-deficient mice that were fed a chow diet and immunized with beta 2-GPI had an accelerated atherosclerosis and that beta 2-GPI was abundantly expressed within subendothelial regions and intimal-medial borders of human atherosclerotic plaques. All of these observations strongly suggest that autoimmune atherogenesis linked to beta 2-GPI interaction with oxLDL and autoantibodies may be present in APS.     

Anti-soluble liver antigen (SLA) antibodies in chronic HCV infection

Hepatitis C infection is associated with autoimmune disorders, such as the production of autoantibodies. Anti-LKM1 and anti-LC1, immunomarkers of type 2 autoimmune hepatitis, have been previously associated with a HCV infection. Anti-Soluble-Liver-Antigen autoantibodies (SLA) are specifically associated with type 1 and type 2 autoimmune hepatitis and more closely related to patients who relapse after steroid therapy. The recent molecular cloning of the soluble liver antigen provides the opportunity to develop more specific tests for the detection of antibodies against it. The aim of this work is to characterize anti-soluble-liver autoantibodies in sera from patients chronically infected by HCV. A recombinant cDNA from activated Jurkat cells coding for the full length tRNP(Ser)Sec/SLA antigen was obtained. ELISA, Western Blot and immunoprecipitation tests were developed and used to search for linear and conformational epitopes recognized by anti-SLA antibodies in sera from patients chronically infected by HCV. Anti-soluble liver antigen antibodies were found in sera from 10.4% of HCV-infected patients. The prevalence was significantly increased to 27% when anti-LKM1 was also present. Most anti-SLA reactivity was directed against conformational epitopes on the antigen. The means titers by ELISA were lower than those obtained in type 2 AIH. The result of autoantibody isotyping showed a subclass restriction to IgG1 and also IgG4. This study shows the presence of anti-SLA antibodies in approximately 10% of HCV infected patients. The prevalence of SLA autoantibodies in HCV infected patients increases when LKM1 autoantibodies are also present. The relationship between the prevalence of this characteristic autoimmune hepatitis autoantibody and the implication of an autoimmune phenomenon in the liver injury of patients chronically infected by HCV needs further investigation.