Anti-actin antibodies in sera from patients with autoimmune liver diseases and patients with carcinomas by ELISA

Easy recognition and high autoimmune hepatitis specificity of smooth muscle antibodies giving an actin microfilament immunofluorescent pattern on embryonal vascular smooth muscle cells

Smooth muscle antibodies (SMA) with anti-microfilament actin (MF-SMA) specificity are regarded as highly specific markers of type 1 autoimmune hepatitis (AIH-1) but their recognition relying on immunofluorescence of vessel, glomeruli, and tubules (SMA-VGT pattern) in rodent kidney tissue, is restricted by operator-dependent interpretation. A gold standard method for their identification is not available. We assessed and compared the diagnostic accuracy for AIH-1 of an embryonal aorta vascular smooth muscle (VSM) cell line-based assay with those of the rodent tissue-based assay for the detection of MF-SMA pattern in AIH-1 patients and controls. Sera from 138 AIH-1 patients and 295 controls (105 primary biliary cholangitis, 40 primary sclerosing cholangitis, 50 chronic viral hepatitis, 20 alcohol-related liver disease, 40 steatotic liver disease, and 40 healthy controls) were assayed for MF-SMA and SMA-VGT using VSM-based and rodent tissue-based assays, respectively. MF-SMA and SMA-VGT were found in 96 (70%) and 87 (63%) AIH-1 patients, and 2 controls (P < 0.0001). Compared with SMA-VGT, MF-SMA showed similar specificity (99%), higher sensitivity (70% vs 63%, P = ns) and likelihood ratio for a positive test (70 vs 65). Nine (7%) AIH-1 patients were MF-SMA positive despite being SMA-VGT negative. Overall agreement between SMA-VGT and MF-SMA was 87% (kappa coefficient 0.870, [0.789-0.952]). MF-SMA were associated with higher serum γ-globulin [26 (12-55) vs 20 g/l (13-34), P < 0.005] and immunoglobulin G (IgG) levels [3155 (1296-7344) vs 2050 mg/dl (1377-3357), P < 0.002]. The easily recognizable IFL MF-SMA pattern on VSM cells strongly correlated with SMA-VGT and has an equally high specificity for AIH-1. Confirmation of these results in other laboratories would support the clinical application of the VSM cell-based assay for reliable detection of AIH-specific SMA.

Biosensing using antibody-modulated motility of actin filaments on myosin-coated surfaces

Motor proteins, such as myosin and kinesin, are biological molecular motors involved in force generation and intracellular transport within living cells. The characteristics of molecular motors, i.e., their motility over long distances, their capacity of transporting cargoes, and their very efficient energy consumption, recommend them as potential operational elements of a new class of dynamic nano-devices, with potential applications in biosensing, analyte concentrators, and biocomputation. A possible design of a biosensor based on protein molecular motor comprises a surface with immobilized motors propelling cytoskeletal filaments, which are decorated with antibodies, presented as side-branches. Upon biomolecular recognition of these branches by secondary antibodies, the 'extensions' on the cytoskeletal filaments can achieve considerable lengths (longer than several diameters of the cytoskeletal filament carrier), thus geometrically impairing or halting motility. Because the filaments are several micrometers long, this sensing mechanism converts an event in the nanometer range, i.e., antibody-antigen sizes, into an event in the micrometer range: the visualization of the halting of motility of microns-long cytoskeletal filaments. Here we demonstrate the proof of concept of a sensing system comprising heavy-mero-myosin immobilized on surfaces propelling actin filaments decorated with actin antibodies, whose movement is halted upon the recognition with secondary anti-actin antibodies. Because antibodies to the actin-myosin system are involved in several rare diseases, the first possible application for such a device may be their prognosis and diagnosis. The results also provide insights into guidelines for designing highly sensitive and very fast biosensors powered by motor proteins.

Autoantibody signatures defined by serological proteome analysis in sera from patients with cholangiocarcinoma

BACKGROUND

The challenging diagnosis and poor prognosis of cholangiocarcinoma require the determination of biomarkers. Autoantibodies could be used in the clinic as diagnostic markers for the early detection of tumours. By proteomic approaches, several autoantibodies were proposed as potential markers. We tried in this study, to perform a serological proteome analysis, using various antigenic substrates, including tumours and human liver.

METHODS

Sera from patients (n = 13) and healthy donors (n = 10) were probed on immunoblots performed using 2-dimensionally separated proteins from cholangiocarcinoma cell lines (CCLP1 and CCSW1), from the liver of healthy subject and interestingly, from tumour and adjacent non-tumour liver tissues from five patients with cholangiocarcinoma and tested with their corresponding serum. Spots of interest were identified using mass spectrometry and classified according gene ontology analysis.

RESULTS

A comparison of the whole immunoblotting patterns given by cholangiocarcinoma sera against those obtained with normal control sera enabled the definition of 862 spots. Forty-five different proteins were further analysed, corresponding to (1) spots stained with more than four of 13 (30 %) sera tested with the CCLP1 or the CCSW1 cell line and with the normal liver, and (2) to spots immunoreactive with at least two of the five sera probed with their tumour and non-tumour counter-part of cholangiocarcinoma. Immunoreactive proteins with catalytic activity as molecular function were detected at rates of 93 and 64 % in liver from healthy subjects or cholangiocarcinoma non-tumour tissues respectively, compared to 43, 33, 33 % in tumour tissues, or CCSW1 and CCLP1 cell lines. A second pattern was represented by structural proteins with rates of 7 and 7 % in normal liver or non-tumour tissues compared to 14, 33 and 67 % in tumour tissue, CCSW1 or CCLP1 cell lines. Proteins with a binding function were detected at rates of 7 % in non-tumour tissue and 14 % in tumour tissue. Using the extracted tumour tissue, serotransferrin was targeted by all cholangiocarcinoma-related sera.

CONCLUSIONS

Immunological patterns depended on the type of antigen substrate used; i.e. tumour versus non tumour specimens. Nevertheless, a combination of multiple autoantibodies tested with the most appropriate substrate might be more sensitive and specific for the diagnosis of cholangiocarcinoma.

Actin is a target of T-cell reactivity in patients with advanced carotid atherosclerotic plaques

Atherosclerosis is a chronic inflammatory disease of the arterial wall associated with autoimmune reactions. In a previous study, we observed the presence of actin-specific antibodies in sera from patients with carotid atherosclerosis. To extend our previous results we evaluated the possible role of actin as antigenic target of cell-mediated immune reactions in carotid atherosclerosis. Peripheral blood mononuclear cells (PBMC) from 17 patients and 16 healthy subjects were tested by cell proliferation assay and by ELISA for cytokine production. Actin induced a proliferative response in 47% of patients' PBMC samples, with SI ranging from 2.6 to 21.1, and in none of the healthy subjects' samples (patients versus healthy subjects, P = 0.02). The presence of diabetes in patients was significantly associated with proliferative response to actin (P = 0.04). IFN-γ and TNF-α concentrations were higher in PBMC from patients than in those from healthy subjects and in PBMC proliferating to actin than in nonproliferating ones. Our data demonstrate for the first time a role of actin as a target autoantigen of cellular immune reactions in patients with carotid atherosclerosis. The preferential proinflammatory Th1 activation suggests that actin could contribute to endothelial dysfunction, tissue damage, and systemic inflammation in carotid atherosclerosis.

Anti-α actinin antibodies as new predictors of response to treatment in autoimmune hepatitis type 1

BACKGROUND

We reported that combined presence of autoantibodies (Abs) against filamentous-actin (AFA) and α-actinin are specific for autoimmune hepatitis type 1 (AIH-1) diagnosis.

AIM

To explore our data and assess whether anti-α-actinin and AFA Abs could be used as indicators of response to treatment and predictors of AIH-1 flares in a large cohort of AIH-1 patients.

METHODS

Seven hundred and sixty-four serial serum samples of 86 consecutive AIH-1 patients, 509 pathological and 110 normal controls were tested for the presence of anti-α-actinin and AFA Abs by an in-house IgG-specific ELISA and a standardised commercially available ELISA respectively. Patients sera were divided into baseline group (active disease before treatment initiation, n = 86) and then according to treatment response into group A-responders (n = 40 patients), group B-relapsers/incomplete responders (n = 37 patients) and group C-not-treated (n = 9 patients).

RESULTS

Anti-α-actinin and AFA levels were significantly higher at baseline. Double reactivity against α-actinin and AFA was associated with disease activity (OR 4.9; 95% CI: 2.7-9). Anti-α-actinin optical densities (ODs) before treatment decreased significantly at first remission (P < 0.05). Treatment response was associated with anti-α-actinin Abs negativity before treatment (OR 3.4; 95% CI: 1.3-8.9) and absence of double positivity for anti-α-actinin and AFA Abs before treatment (OR 3.8; 95% CI: 1.4-10.4). Responders had lower baseline levels of anti-α-actinin than relapsers and/or incomplete responders (P = 0.002). Binary logistic regression revealed lower levels of anti-α-actinin as the only independent predictors of response (P = 0.05).

CONCLUSIONS

Anti-α-actinin Abs at baseline appear to predict treatment response and therefore they might be used for monitoring treatment outcome in AIH-1.

Improved diagnoses of autoimmune hepatitis using an anti-actin ELISA

The presence of antismooth muscle antibodies is one of the diagnostic criteria of autoimmune hepatitis. We evaluated a new anti-F-actin ELISA test and compared it with indirect immunofluorescence assay (IIFA) for antismooth muscle antibodies (ASMA). Two hundred and nine serum samples (35 autoimmune hepatitis, 174 other hepatopathies and control sera) were tested by IIFA on mouse stomach kidney sections for ASMA and by the Quanta Lite Actin ELISA for anti-F-actin antibodies. ASMA were detected in 26 of 35 sera from autoimmune hepatitis (74%) as compared with 25 (71%) with anti-actin antibodies, as well as in 25 of 49 (51%) samples from viral hepatitis as compared with 7 (14%) with anti-actin antibodies. With regards to autoimmune hepatitis, though sensitivity (74.3 vs 71.4%) and negative predictive value (93.5 vs 93.9%) of ASMA and anti-actin ELISA were comparable, anti-actin ELISA was significantly better than ASMA IIFA in terms of specificity (89.7 vs 74.7%), and positive predictive value (58.1 vs 37.1%). Although frequently positive in HCV samples, a comparable sensitivity but better specificity makes the anti-actin ELISA a useful tool in combination with ASMA IIFA for the screening and diagnosis of autoimmune hepatitis.

Anti-alpha-actinin antibodies cross-react with anti-ssDNA antibodies in active autoimmune hepatitis

Recently, we have observed that the association of anti-F-actin autoantibodies (Abs) with anti-alpha-actinin Abs (double reactivity) was correlated with liver disease activity in autoimmune hepatitis type 1 (AIH-1; Guéguen et al., J Clin Immunol 26:495-505, 2006). As anti-alpha-actinin Abs are also associated with anti-single-stranded (ss) DNA in 16 of 50 (32%) AIH-1 patients, compared with 16 of 401 (4.0%) liver disease control patients, we sought to characterize these Abs in AIH-1. When associated, anti-ssDNA Abs cross-react with anti-alpha-actinin Abs, but neither with anti-double-stranded DNA Abs nor with anti-F-actin Abs. Furthermore, anti-alpha-actinin Abs are associated with high-avidity anti-ssDNA Abs in AIH-1. In addition, double reactivity against alpha-actinin and ssDNA was correlated with clinical and histological activity of the disease and untreated AIH-1 patients.

Diagnostic accuracy of four different immunological methods for the detection of anti-F-actin autoantibodies in type 1 autoimmune hepatitis and other liver-related disorders

BACKGROUND

Smooth muscle antibodies (SMA) with anti-F-actin specificity are commonly regarded as specific markers of type 1 autoimmune hepatitis (AIH-1) but, at the moment, a gold standard method for their identification is not available.

OBJECTIVES

To evaluate the diagnostic accuracy for AIH-1 of three new methods of detecting anti-F-actin antibodies, and to compare the results with those obtained using the indirect immunofluorescence (IIF) method on rodent tissue.

METHODS

The sera of 33 AIH-1 patients and 104 controls (eight with type 2 AIH, 30 with chronic hepatitis C, 16 with celiac disease, 40 with primary biliary cirrhosis, and 10 with liver steatosis) were assayed for anti-F-actin antibodies using four methods: two IIF methods (one on rat tissue sections and the other on VSM 47 cell line derived from the thoracic aorta of rat embryo), an ELISA method and an Immunodot (ID) method.

RESULTS

The diagnostic sensitivity, specificity, positive predictive value and negative predictive value were, respectively, 51.5, 95.2, 77.3 and 86.1% for IIF on the VSM 47 cell line; 63.6, 86.5, 60 and 88.2% for the ELISA method; 72.7, 82.7, 57.1 and 90.5% for the ID assay; and 57.6, 96.1, 82.6 and 87.7% for the IIF on rat tissue sections.

CONCLUSION

The methods used for anti-F-actin antibody detection have different diagnostic performances. Both IIF methods, the one on rat tissues and the other on VSM47 cell line, are highly specific for AIH-1. In contrast, ELISA and especially ID show positive results in control population, although usually at low levels (with the single exception of PBC patients). Therefore, having a high positive predictive value, both IIF methods are reliable tools for the specific detection of AIH-associated anti-F-actin autoantibodies, whereas the immunometric assays might be integrated into the diagnostic scheme as second level tests upon improvement of their respective cut-offs to confirm anti-F-actin positivity in case of SMA positivity.

Evaluation of F-actin ELISA for the diagnosis of autoimmune hepatitis

OBJECTIVE

Antibodies to F-actin have been proposed to increase specificity in the diagnosis of autoimmune hepatitis (AIH). We compared the diagnostic value of a new F-actin enzyme-linked immunosorbent assay (ELISA) with the current gold standard of detection of smooth muscle antibodies by indirect immunofluorescence (SMA-IFT).

METHODS

Archived sera of 47 patients with SMA positive AIH were tested with the F-actin ELISA and SMA-IFT. Prospectively collected sera of 123 patients with various liver diseases, 35 of whom had AIH, were analyzed by both assays. Different cutoff limits were considered for the F-actin ELISA (increments between 20 and 60 ELISA units) and SMA-IFT (titers of 1:40, 1:80, and 1:160).

RESULTS

The F-actin ELISA had a sensitivity of 100% to detect all of 47 SMA positive AIH sera and the value of the ELISA units correlated with that of SMA titers (p < 0.0001). In prospective analysis, F-actin ELISA showed a superior sensitivity (74% vs 34%) and a similar specificity (98% vs 99%) and positive predictive value (88% vs 92%), compared with SMA-IFT. Combining both assays improved neither sensitivity nor specificity.

CONCLUSIONS

The new F-actin ELISA seems to be a useful diagnostic tool with similar specificity and superior sensitivity for the diagnosis of AIH, compared with standard SMA-IFT. Due to its simplicity and operator independency, the F-actin ELISA may become a preferred screening technique for detection of autoantibodies in patients with suspected AIH.

Detection of autoantibodies for diagnosis of autoimmune hepatitis

AIM: To evaluate the clinical significance of autoantibody detection in the diagnosis of autoimmune hepatitis (AIH).

METHODS: Indirect immunofluorescence was used to detect the expression of anti-nuclear antibody (ANA), anti-smooth muscle antibody (SMA), antineutropil cytoplasmic antibody (ANCA), and anti-mitochondrial antibody (AMA) in patients with autoimmune hepatitis (AIH, n = 47), non-autoimmune hepatitis (n = 158) and healthy controls (n = 40). Enzyme linked immunosorbent assay (ELISA) was used to examine the content of anti-myeloperoxidase (MPO) antibody. The result was retrospectively analyzed.

RESULTS: Comparison between the rates of ANA, SMA and ANCA showed that SMA was found the highest in AIH patients (66.0%, 31/47), significantly higher than that in non-AIH patients (6.3%, 10/158). After chi-square test, SMA and AMA and MPO were markedly different between AIH and primary biliary cirrhosis (PBC) patients (P < 0.01). Finally, ANA, SMA and ANCA were correlated with AIH-Ⅰ, anti-liver/kidney microsomal antibody (LKM) with AIH-Ⅱ, and anti-soluble liver antigen antibody (SLA), ANCA with AIH-Ⅲ.

CONCLUSION: Detection of autoantibodies is helpful in the diagnosis and therapy of AIH.

Double reactivity against actin and alpha-actinin defines a severe form of autoimmune hepatitis type 1

Anti-filamentous actin antibodies characterize autoimmune hepatitis type 1 (AIH-1). Recently, the binding domain of alpha-actinin on actin was shown to be a predominant epitope. To test this reactivity, an anti-alpha-actinin enzyme-linked immunosorbent assay was developed, and positivity confirmed by Western blot. Anti-alpha-actinin antibody was found in 21/50 (42%) of AIH-1 patients, compared with 52/401 (12.9%) of liver disease control patients, and with 6/200 (6%) of blood donors. Anti-filamentous and anti-alpha-actinin activities were found specifically together in 66% of anti-filamentous-positive AIH-1 patients. This combination of specificities reflected clinical and histological disease activity, short duration and absence of treatment. Finally, using an actin-alpha-actinin complex assay, the binding of anti-filamentous actin to alpha-actinin-binding domain on actin was demonstrated, as well as that of anti-alpha-actinin on the actin-binding domain of alpha-actinin. Thus, the frequent combination of anti-filamentous and anti-alpha-actinin antibodies seems to be the hallmark of activity in AIH-1.

Antibodies to filamentous actin (F-actin) in type 1 autoimmune hepatitis

AIMS

To evaluate the diagnostic significance of anti-filamentous actin antibodies (A-FAA) assessed with a commercial ELISA in comparison with immunofluorescence reactivity and patterns of anti-smooth muscle antibodies (SMA); and to correlate A-FAA positivity with clinical, immunogenetic, laboratory, and histological features in patients with autoimmune hepatitis type 1 (AIH-1).

METHODS

We studied 78 consecutive untreated AIH-1 patients and 160 controls: 22 with autoimmune hepatitis type 2 (AIH-2), 51 with hepatitis C, 17 with coeliac disease (CD), 20 with primary biliary cirrhosis (PBC) and 50 blood donors. SMA was evaluated by indirect immunofluorescence (IIF) on frozen sections of rat tissues, and A-FAA with a modified commercial ELISA.

RESULTS

SMA was detected by IIF in 61 (78%) of 78 AIH-1 patients, of whom 47 (60%) had the SMA-T/G and 14 (18%) the SMA-V pattern. Of the pathological controls, 32 (20%) had the SMA-V pattern (25 with hepatitis C, 2 with AIH-2, 2 with PBC, 3 with CD). A-FAA were present in 55 AIH-1 patients (70.5%; 46 with SMA-T/G, 7 with SMA-V, and 2 SMA-negative), and in 10 controls (6%), of whom five had hepatitis C, two AIH-2, two PBC and one CD. The association between A-FAA and the SMA-T/G pattern was statistically significant (p<0.0001). A-FAA levels were higher in SMA-T/G positive than SMA-V positive AIH-1 patients and controls (p<0.0001). A-FAA positivity was significantly associated with higher gamma-globulin and IgG levels, but did not correlate with other considered parameters.

CONCLUSION

The modified A-FAA ELISA strictly correlates with the SMA-T/G pattern and is a reliable and operator independent assay for AIH-1. Detection of A-FAA, even if devoid of prognostic relevance, may be useful when interpretative doubts of standard IIF arise.

Proteomic Scan for Tyrosinase Peptide Antigenic Pattern in Vitiligo and Melanoma: Role of Sequence Similarity and HLA-DR1 Affinity

Immune responses contribute to the pathogenesis of vitiligo and target melanoma sometimes associated with vitiligo-like depigmentation in some melanoma patients. We analyzed the sera from patients with vitiligo and cutaneous melanoma for reactivity toward tyrosinase peptide sequences 1) endowed with low level of similarity to human proteome, and 2) potentially able to bind HLA-DR1 Ags. We report that the tyrosinase autoantigen was immunorecognized with the same molecular pattern by sera from vitiligo and melanoma patients. Five autoantigen peptides composed the immunodominant anti-tyrosinase response: aa95-104FMGFNCGNCK; aa175-182 LFVWMHYY; aa176-190FVWMHYYVSMDALLG; aa222-236IQKLTGDENFTIPYW, and aa233-247 IPYWDWRDAEKCDIC. All of the five antigenic peptides were characterized by being (or containing) a sequence with low similarity level to the self proteome. Sera from healthy subjects were responsive to aa95-104FMGFNCGNCK, aa222-236IQKLTGDENFTIPYW, and aa233-247 IPYWDWRDAEKCDIC, but did not react with the aa175-182LFVWMHYY and aa176-190FVWMHYYVSMDALLG peptide sequences containing the copper-binding His180 and the oculocutaneous albinism I-A variant position F176. Our results indicate a clear-cut link between peptide immunogenicity and low similarity level of the corresponding amino acid sequence, and are an example of a comparative analysis that might allow to comprehensively distinguish the epitopic peptide sequences within a disease from those associated to natural autoantibodies. In particular, these data, for the first time, delineate the linear B epitope pattern on tyrosinase autoantigen and provide definitive evidence of humoral immune responses against tyrosinase.

Identification of CLP36 as a tumor antigen that induces an antibody response in pancreatic cancer

PURPOSE

Pancreatic cancer has a poor prognosis, due in part to the lack of an effective approach for its early detection. The identification of tumor antigens potentially provides a means for the early diagnosis. The purpose of this study was to use a proteomic approach for the identification of proteins that commonly induce a humoral response in patients with pancreatic cancer.

MATERIALS AND METHODS

Proteins from the pancreatic adenocarcinoma cell line, BxPC3, were subjected to two-dimensional polyacrylamide gel electrophoresis, followed by Western blot analysis, where individual sera were tested for autoantibodies. Sera from 36 patients with pancreatic adenocarcinoma, and 68 from control groups (14 from lung adenocarcinoma, 19 from colon adenocarcinoma and 35 from healthy subjects) were analyzed. CLP36 expression was evaluated by immunohistochemical analysis and real-time PCR. The cellular localization of CLP36 as an autoantigen was investigated by Western blot analysis.

RESULTS

The autoantibody was detected against a protein, identified by mass spectrometry as CLP36, in 14 of the 36 sera (38.9%) from patients with a pancreatic adenocarcinoma, and 3 of the 68 controls (4.4%). Immunohistochemical analysis of CLP36 in a tissue array demonstrated diffuse and consistent immunoreactivity in the pancreatic adenocarcinomas. The levels of CLP36 mRNA were highest in the pancreatic cancer cell lines of the different cells analyzed. The molecular weight of the protein displayed in the membrane-rich fraction was larger than that in the cytosolic fraction, which is likely attributable to a post-translational modification.

CONCLUSION

CLP36 was identified as a tumor autoantigen inducing a humoral immune response in pancreatic adenocarcinomas. More detailed studies need to be undertaken to understand whether the humoral response by CLP36 is tumor-specific.

IgG from patients with liver diseases inhibit mitochondrial respiration in permeabilized oxidative muscle cells: impaired function of intracellular energetic units?

The effect of IgG purified from the sera of healthy persons and patients with primary biliary cirrhosis (PBC) and chronic hepatitis (CH) on ADP dependent respiration (oxidative phosphorylation) in skinned muscle fibers from rat oxidative muscles (heart and M. soleus) and glycolytic skeletal muscle (M. gastrocnemius) was studied. The results show that IgG from three different sources inhibited the rate of respiration by 13, 44 and 42%, respectively, these effects being equally expressed in both types of oxidative muscles, whereas no inhibition was observed in glycolytic muscle. The following washout of unbound IgG did not abolish the inhibition of respiration suggesting that the specific interaction of IgG with antigens had taken place. Laser confocal analysis revealed binding of IgG predominantly to the sarcomeric structures such as Z-disk and M-lines in the cardiomyocytes. The staining of IgG within Z-disks and intermitochondrial space coincided throughout the muscle cells so that transversally serial spaces, each containing mitochondria and adjacent sarcomere, became clearly visible. When the IgG from a CH patient was incubated with the skinned myocardial fibers of the desmin knockout mice, its binding to Z-disks and the sarcomeric area was found to be similar to that in normal cardiac muscle. However, the transversal staining pattern was disintegrated, because of the slippage of the myofibrils in relation to each other and accumulation of mitochondria between them. These observations support the recent hypothesis that in oxidative muscles the mitochondria and adjacent sarcomeres form complexes, termed as the intracellular energetic units, ICEUs. Moreover, they indicate that human autoantibodies can be useful tools for localizing the proteins responsible for formation of ICEUs and modulation of their function. Thus, it appears that the proteins associated with the Z-disks and M-lines may participate in formation of ICEUs and that binding of IgG to these proteins decreases the access of exogenous adenine nucleotides to mitochondria, which manifests as decreased rate of ADP-dependent respiration.

Screening of a HUAEC cDNA library identifies actin as a candidate autoantigen associated with carotid atherosclerosis

The humoral immune response to endothelium has a pivotal role in the development of atherosclerosis. Using a molecular method, we sought to identify endothelial autoantigens in carotid atherosclerosis. Immunoscreening of a HUAEC expression library with IgG from a pool of two sera from patients with carotid atherosclerosis identified a clone specific to actin. We evaluated actin-specific IgG reactivity in patients with carotid atherosclerosis and compared responses with those in patients with systemic lupus erythematosus and type 1 diabetes mellitus and in healthy subjects. Enzyme-linked immunoassay detected actin-specific IgG in a significantly higher percentage of sera from patients with atherosclerosis and systemic lupus erythematosus than from healthy subjects (16/61, 26% and 13/33, 39%versus 2/41, 5%, P = 0.012 and P < 10(-4), by chi2 test). Mean optical density values were significantly higher in patients than in healthy subjects (P < 10(-4) by Student's t-test). Patients with atherosclerosis and uncomplicated plaques had significantly higher serum anti-actin IgG reactivity than those with complicated plaques (P = 0.048 by Student's t-test). Our findings suggest that actin is an autoantigenic molecule of potential clinical interest in carotid atherosclerosis.

Translocation of an intracellular antigen to the surface of medullary breast cancer cells early in apoptosis allows for an antigen-driven antibody response elicited by tumor-infiltrating B cells

Tumor-infiltrating lymphoplasmacytic cells are a key feature of medullary carcinoma of the breast (MCB), a distinct subtype of human breast cancer that, despite cytologically anaplastic characteristics, has a more favorable prognosis than other types of breast cancer. Since it has been proposed that the improved clinical outcome is due at least in part to the presence of a prominent lymphoplasmacytic cell infiltrate in the tumor stroma, we recently examined the tumor-infiltrating B cell response in MCB and showed that it is oligoclonal and directed against an intracellular protein translocated to the cell surface upon MCB cell apoptosis. Human Abs cloned from MCB lymphoplasmacytic infiltrate-derived phage display libraries and reflecting the dominant part of the response were used to identify the target Ag as actin. Here, we have characterized in detail the cloned human IgG Abs and the translocation process of actin to the cell surface of apoptotic MCB cells. Our analysis shows that the cloned Abs bind specifically and with high affinity to actin, as determined by ELISA and surface plasmon resonance. Sequence analysis revealed that the Abs are highly somatically mutated, with high replacement to silent ratios, indicative of an Ag-driven, affinity-matured response. Interestingly, the tumor-infiltrating B cells in half the MCB patients mainly exhibited an IgG2 response, while IgG1 dominated in the others. To gain insight to the molecular events that may elicit such an Ab response, we examined the translocation of actin to the cell surface of apoptotic MCB cells using flow cytometry and laser scanning cytometry. Our results show that actin becomes exposed on the cell surface of a large proportion of apoptotic MCB cells as an early apoptotic event. We propose that the Ab response against actin produced by tumor-infiltrating B lymphoplasmacytic cells is Ag-driven, affinity-matured, and elicited due to the increased rate of apoptosis occurring within the MCB tumor that facilitates the translocation and proteolytic fragmentation of intracellular proteins.

Variant syndromes of autoimmune hepatitis

The diagnostic criteria for each of the three major autoimmune liver diseases must be codified and the boundaries between diseases established. There will always be syndromes with mixed or atypical features because classically defined disorders represent only the outer ends of the diagnostic spectrum. It is only after boundaries have been decided by consensus that the true variants of autoimmune liver disease can be appreciated. Until then, both the diagnosis and treatment of these syndromes will be arbitrary and unclear.

Anti-smooth muscle antibodies (ASMAs) and anti-cytoskeleton antibodies (ACTAs) in liver diseases: a comparison of classical indirect immunofluorescence with ELISA

In the diagnosis of autoimmune hepatitis type I (AIH-I), the routine assay of indirect immunofluorescence (IFL), used for the detection of anti-smooth muscle antibodies (ASMAs), has a low predictive value. On the other hand, the enzyme-linked immunosorbent assay (ELISA), which detects anti-cytoskeleton antibodies (ACTAs), presents contradictory results concerning their specific antigenic target. In this study, we first looked for the immunological properties (isotypes and antigenic targets) of autoantibodies in AIH-I and two other control liver diseases: primary biliary cirrhosis (PBC) and viral hepatitis (VH), using ELISA based on cytoskeleton proteins: F-actin, G-actin, myosin, tropomyosin, troponin, desmin, vimentin, keratin, and an extract of HEp-2 carcinoma cells. We also compared the diagnostic value of IFL and ELISA. In contrast to previous studies, we found that actin was not specific for AIH-I. No autoantigen and no antibody class or subclass discriminated AIH-I from the control diseases. IFL is more suitable for AIH-I diagnosis, as 97% of AIH-I sera but only 22% of PBC sera were ASMA-positive. Additionally, 96% of ASMA-positive, and all ASMA-negative sera from all three liver diseases were ACTA-positive. ASMA were mainly IgG, while >50% of ACTA also contained IgA and IgM. These data suggest that ACTAs recognize additional epitopes as compared to ASMAs, and they frequently occur in all liver diseases.

Cancer and autoimmunity: autoimmune and rheumatic features in patients with malignancies

OBJECTIVES

To review the autoimmune and rheumatic manifestations of patients with malignancy.

METHODS

A Medline search of all published papers using keywords related to malignancies, autoimmunity, rheumatic diseases, and paraneoplastic syndromes.

RESULTS

Patients with malignant diseases may develop autoimmune phenomena and rheumatic diseases as a result of (a) generation of autoantibodies against various autoantigens, including oncoproteins (P185, 1-myc, c-myc, c-myb), tumour suppression genes (P53), proliferation associated antigens (cyclin A, B1, D1, E; CENP-F; CDK, U3-RNP), onconeural antigens (Hu, Yo, Ri, Tr), cancer/testis antigens (MAGE, GAGE, BAGE, SSX, ESO, SCP, CT7), and rheumatic disease associated antigens (RNP, Sm). The clinical significance of the various autoantibodies is not clear. Anti-oncoprotein and anti-tumour suppression gene antigens are detected before the diagnosis of the cancer or in the early stages of the malignant disease, suggesting a potential diagnostic or prognostic role. Anti-onconeural antibodies are pathogenic and are associated with specific clinical neurological syndromes (anti-Hu syndrome and others). (b) Paraneoplastic syndromes, a wide range of clinical syndromes, including classic autoimmune rheumatic diseases that develop among patients with cancer. (c) Rheumatism after chemotherapy, a clinical entity characterised by the development of musculoskeletal symptoms after combination chemotherapy for malignancy.

CONCLUSION

Autoimmune and rheumatic features are not rare among patients with malignancies. They are the result of various diverse mechanisms and occasionally they may be associated with serious clinical entities.

Death, autoantigen modifications, and tolerance

Autoantibodies present in the serum of patients with a variety of inflammatory diseases have proven useful as diagnostic markers and as probes with which to elucidate biochemical and signaling pathways. The mechanisms governing the generation of autoantibodies remain elusive, constituting a critical missing link in our understanding of rheumatologic illnesses. Several lines of experimentation in recent years have strongly implicated events surrounding cell death in this process. This review will address the potential role played by death-specific modifications of autoantigens in bypassing tolerance to highly conserved autoantigens, including nucleic acids, lipids, and proteins.