HLA class II influences humoral autoimmunity in patients with type 2 autoimmune hepatitis

BACKGROUND/AIMS: Type 2 autoimmune hepatitis (AIH) is characterized by the presence of anti-liver kidney microsome (anti-LKM-1) and/or anti-liver cytosol type 1 (anti-LC1) autoantibodies. However, the correlation between these autoantibodies and the genetic background has not been studied. METHODS: Frequencies of HLA class II alleles were compared between the 60 Caucasian children with type 2 AIH and 313 control subjects. The anti-LKM1 antibody reactivity directed against antigenic sites of CYP2D6 was analysed by ELISA. RESULTS: HLA-DQB1 *0201 allele was found to be the primary genetic determinant of susceptibility to type 2 AIH by conferring the highest odd-ratio (OR = 6.4). HLA-DRB1 *03 allele was significantly increased (P < 0.0001) among patients with both anti-LKM1 and anti-LC1 autoantibodies as well as in those with only anti-LC1(+) compared to those with anti-LKM1(+) alone. In contrast, HLA-DRB1 *07 allele was significantly associated (P < 0.0001) with anti-LKM1(+) alone compared to groups with both anti-LKM and anti-LC1 or with LC1+ alone. Children with the DRB1 *07 allele develop anti-LKM1 autoantibodies having a more restricted specificity (2 epitopes) than to those having HLA-DRB1 *03 allele (5 epitopes). CONCLUSIONS: The HLA-DR locus is involved in autoantibody expression, while the DQ locus appears to be a critical determinant for the development of type 2 AIH.     

Frequency and significance of antibodies to liver/kidney microsome type 1 in adults with chronic active hepatitis.

To assess the frequency of antibodies to liver/kidney microsome type 1 (anti-LKM1) in patients with chronic active hepatitis, 131 such patients were tested by an indirect immunofluorescence assay. Of 62 patients with type 1 autoimmune hepatitis, none were seropositive. In contrast, 3 of 11 patients with autoimmune hepatitis and antimitochondrial antibodies (27%) were seropositive for anti-LKM1. Each had responded to corticosteroid therapy, and retesting of sera confirmed that each had been misclassified as antimitochondrial antibody positive. None of the patients with chronic active hepatitis B (14 patients) or C (24 patients) had anti-LKM1. Similarly, none of the 20 patients with cryptogenic disease had these antibodies. It is concluded that anti-LKM1 is specific for type 2 autoimmune hepatitis and is infrequent in adult patients seen at a referral center in the United States for chronic active hepatitis. Anti-LKM1 reactivity may be misinterpreted as antimitochondrial antibody reactivity by indirect immunofluorescence. Chronic hepatitis B and C virus infections are not important stimuli for the production of anti-LKM1, and testing for anti-LKM 1 is unlikely to clarify the nature of cryptogenic disease.     

Anti-liver cytosolic antigen type 1 (LC1) antibodies in childhood autoimmune liver disease

Antibodies to liver cytosol antigen type 1 (anti-LC1), which recognize a 60-kd peptide contained in the liver cytosolic fraction, have been reported to define a subset of autoimmune hepatitis (AIH) either negative for other autoantibodies or positive for anti-liver kidney microsomal antibody type 1 (LKM-1) and to be best detected in immunodiffusion. To analyze the prevalence of antiLC1 in childhood liver disease, we have tested the sera of 95 patients using immunoblot, indirect immunofluorescence, and immunodiffusion. Fifteen children had smooth muscle antibody (SMA) and/or anti-nuclear antibody (ANA)-positive AIH, 13 had anti-LKM-1-positive AIH, 14 had autoimmune sclerosing cholangitis (ASC) (all SMA and/or ANA positive), and 53 had non-autoimmune liver disease (10 had al-anti-trypsin deficiency [α1-ATD], 11 had Wilson's disease [wd], 14 had Alagille's syndrome, and 18 had chronic hepatitis B virus [HBV] infection). Twenty healthy children were studied as controls. Anti-LC1 positivity in immunodiffusion and strong reactivity in immunoblot were found in 4 LKM-1- and 2 SMA/ANA-positive patients with AIH and in 1 patient with ASC, but in none of the patients with other liver diseases nor in controls. A weak 60-kd band was detected by immunoblot in 6 more patients with AIH (2 were LKM-1- and 4 were SMA/ANA-positive) and 6 patients with ASC, all anti-LC1-negative by immunofluorescence and immunodiffusion. No distinct clinical features characterized the anti-LC1-positive patients. Our data show that, in pediatric age, LC1 reactivity, although associated with autoimmune liver disease, does not identify a distinct disease subset and that immunoblot is the most sensitive technique to detect anti-LC1.     

Liver cytosolic 1 antigen-antibody system in type 2 autoimmune hepatitis and hepatitis C virus infection.

Within the multiform liver/kidney microsomal (LKM) family, a subgroup of sera that reacts with a liver cytosolic (LC) protein has been isolated and the new antigen-antibody system is called LC1. Unlike LKM antibody type 1 (anti-LKM1), anti-LC1 is said to be unrelated to hepatitis C virus (HCV) infection and has therefore been proposed as a marker of 'true' autoimmune hepatitis type 2. Altogether 100 LKM1 positive sera were tested by immunodiffusion (ID). Twenty five gave a precipitation line with human liver cytosol; 17 of the 25 also reacted with rat liver cytosol. Thirteen of the 25 sera were anti-HCV positive by second generation ELISA: anti-HCV positive patients were significantly older (p < 0.001) and tended to have less active disease. No difference in anti-LC1 titre or ID immunoreactivity was found between anti-LC1/anti-HCV positive and anti-LC1/anti-HCV negative cases. In Western blotting experiments, 14 of 24 ID positive sera recognised a 58 kD protein of the human cytosolic fraction and 11 gave a similar reactivity when tested with human microsomes, suggesting the presence of the LC1 target antigen also in the microsomal preparation. Western blotting reactivity was similar for both anti-HCV positive and negative sera. These data confirm the existence of the LC1 antigen-antibody system that partially overlaps with LKM1, and that it is an additional marker of juvenile autoimmune hepatitis type 2. It does not, however, discriminate between patients with and without HCV infection.     

Autoimmune serology in liver disease: methodology and interpretation

Abstract   Accurate measurement of levels of autoantibodies in serum is critical for the diagnosis of autoimmune hepatitis. The major reactivities include anti-nuclear antibody (ANA), smooth muscle antibody (SMA), antibody to liver kidney microsomes type-1 (anti-LKM1); other relevant reactivities include antibodies to liver cytosol 1 (anti-LC1), soluble liver antigen (anti-SLA), and neutrophil cytoplasmic antigens (ANCA). In addition to the classical indirect immunofluorescence technique, automatic assays based on recombinant antigens are now available, which allow detection of antibodies not visible on immunofluorescence, like anti-SLA, and assist in the interpretation of at times problematic immunofluorescence patterns, like anti-LKM1 or anti-LC1.     

慢性肝病中抗肝抗原自身抗体的检测

目的　探讨中国人不同病因所致慢性肝病患者中抗肝抗原自身抗体的存在状况及自身免疫性肝病的自身抗体特征。方法　 166例肝功能异常患者分为 6组 :自身免疫性肝炎 (AIH ) 12例、原发性胆汁性肝硬化 (PBC) 2 0例、原发性硬化性胆管炎 (PSC)13例、HBV组 66例、HCV组 2 2例、肝豆状核变性 (HDL) 3 9例。用间接免疫荧光法检测抗核抗体 (ANA)、平滑肌抗体 (SMA)、抗肝肾微粒抗体I型抗体 (anti LKM1)、抗线粒体抗体 (AMA)和抗中性粒细胞胞浆抗体 (ANCA) ,免疫印迹法检测抗肝细胞胞溶质抗原 1型抗体 (anti_LC1)、抗可溶性肝抗原 /肝胰抗原抗体 (anti_SLA/LP)、抗肝肾微粒抗体 1型 (anti_LKM1)、AMA_M2亚型等多种肝抗原自身抗体。结果　 166例中ANA、AMA、M_2、pANCA阳性率在 7组中有显著差异 (P <0 .0 1)。PBC中AMA、M 2阳性检出率均为 10 0 % ,PSC中pANCA阳性检出率为 5 3 8% ,Fisher精确检验在a =0 .0 0 2水准与其他各组比较有显著差异。AIH与PBC的ANA阳性率分别为10 0 %和 60 % ,Fisher精确检验在a =0 .0 0 2水准二者无显著差异。与其他各组比较有显著差异。在AIH组SMA阳性率为 2 5 % ,LKM 1、LC 1、SLA/LP阳性率均为 8.3 % ,统计学处理与其他组无显著差异 (P >0 0 5 ) ,可能与病例少有关。PBC中分别有 1     

A murine model of type 2 autoimmune hepatitis: Xenoimmunization with human antigens

Autoimmune hepatitis (AIH) is characterized by an immune-mediated injury of the hepatic parenchyma of unknown pathogenesis. Type 2 AIH is identified by the presence of anti-liver-kidney microsomes type 1 (anti-LKM1) and anti-liver cytosol type 1 (anti-LC1) autoantibodies. The current study shows that a murine model of AIH can be generated by DNA immunization against type 2 AIH self-antigens (P450 2D6 and formiminotransferase-cyclodeaminase). A pCMV plasmid containing the N-terminal region of mouse CTLA-4 and the antigenic region of human CYP2D6 (672-1,377 bp) and human formiminotransferase cyclodeaminase (FTCD; 1,232-1,668 bp) was used for DNA immunization of C57BL/6 female mice. Immunized mice showed elevated levels of alanine aminotransferase (ALT), with peaks at 4 and 7 months postinjection. Periportal, portal, and intralobular liver inflammatory infiltrates were observed at histology. Mainly CD4+ lymphocytes, but also CD8+ and B lymphocytes, were found in the liver. Cytotoxic-specific T cells were found in both the liver and spleen of these animals. Mice developed anti-LKM1 and anti-LC1 antibodies of immunoglobulin G2 (IgG2) subclass, against specific mouse autoantigens. The ALT levels correlated with both the presence of anti-LKM1/anti-LC1 antibodies and the presence of liver necroinflammation. In conclusion, in mice, DNA immunization against human autoantigens breaks tolerance and induces an autoimmune liver disease. Molecular mimicry between foreign and self-antigens explains the liver injury. This model of AIH resembles human type 2 AIH and will be helpful for the study of its pathogenesis.     

Hepatocyte membrane-bound IgG and circulating liver-specific autoantibodies in chronic liver disease: relation to hepatitis B virus serum markers and liver histology

Hepatocytes isolated from 101 biopsies were examined for membrane-bound IgG. The sera of the patients were tested for anti-liver-specific lipoprotein by radioimmunoassay and for liver membrane autoantibody (by indirect immunofluorescence on isolated rabbit hepatocytes. The seven patients with normal liver or minor nonspecific alterations were negative for membrane IgG and serum antibodies. Membrane IgG with granular distribution was found in 41 patients [21 hepatitis B virus-related chronic active hepatitis (CAH), 3 cryptogenic CAH, 3 chronic persistent hepatitis, 6 prolonged viral hepatitis, 1 alcoholic cirrhosis, and 6 primary biliary cirrhosis]. Membrane IgG with linear fluorescence pattern was detected in 12 cases (4 autoimmune CAH, 3 HBsAg-positive CAH, 2 alcoholic cirrhosis, 1 anti-HBc positive CAH, 1 cryptogenic CAH, and 1 prolonged viral hepatitis). A strong association between granular IgG and serum HBsAg was found. Nuclear localization of IgG was found in 34 patients and correlated with the positivity of granular membrane IgG. The highest prevalence of anti-liver-specific lipoprotein was found in primary biliary cirrhosis and autoimmune CAH cases which were also positive for liver membrane autoantibody. No relationship was found between the presence of membrane IgG and circulating liver-specific autoantibodies. Membrane IgG and anti-liver-specific lipoprotein correlated with the presence of moderate and severe portal inflammatory infiltration but not with piecemeal necrosis or transaminase levels. Eleven of the twelve patients with linear membrane IgG presented chronic active liver disease with moderate to severe signs of liver damage. Therefore, it is suggested that, while granular membrane IgGs are related to hepatitis B virus, antigenic expression on the hepatocyte surface and/or the presence of immune complexes, linear membrane IgG could play a role in the immunopathogenesis of liver cell damage particularly in "autoimmune" cases which present high percentages of positive cells liver-specific autoantibodies.     

Autoimmune liver serology：Current diagnostic and clinical challenges

Liver-related autoantibodies are crucial for the correct diagnosis and classification of autoimmune liver diseases（AiLD）,namely autoimmune hepatitis types 1 and 2（AIH-1 and 2）,primary biliary cirrhosis（PBC）,and the sclerosing cholangitis variants in adults and children.AIH-1 is specified by anti-nuclear antibody（ANA） and smooth muscle antibody（SMA）.AIH-2 is specified by antibody to liver kidney microsomal antigen type-1（anti-LKM1） and anti-liver cytosol type 1（anti-LC1）.SMA,ANA and anti-LKM antibodies can be present in de-novo AIH following liver transplantation.PBC is specified by antimitochondrial antibodies（AMA） reacting with enzymes of the 2-oxo-acid dehydrogenase complexes（chiefly pyruvate dehydrogenase complex E2 subunit） and disease-specific ANA mainly react-ing with nuclear pore gp210 and nuclear body sp100.Sclerosing cholangitis presents as at least two variants,first the classical primary sclerosing cholangitis（PSC） mostly affecting adult men wherein the only（and non-specific） reactivity is an atypical perinuclear antineutro-phil cytoplasmic antibody（p-ANCA）,also termed perinuclear anti-neutrophil nuclear antibodies（p-ANNA） and second the childhood disease called autoimmune sclerosing cholangitis（ASC） with serological features resembling those of type 1 AIH.Liver diagnostic serology is a fast-expanding area of investigation as new purified and recombinant autoantigens,and automatedtechnologies such as ELISAs and bead assays,become available to complement（or even compete with） traditional immunofluorescence procedures.We survey for the first time global trends in quality assurance impacting as it does on（1） manufacturers/purveyors of kits and reagents,（2） diagnostic service laboratories that fulfill clinicians＇ requirements,and（3） the end-user,the physician providing patient care,who must properly interpret test results in the overall clinical context.     

Antibodies against human cytochrome P-450db1 in autoimmune hepatitis type II.

In a subgroup of children with chronic active hepatitis, circulating autoantibodies occur that bind to liver and kidney endoplasmic reticulum (anti-liver/kidney microsome antibody type I or anti-LKM1). Anti-LKM1 titers follow the severity of the disease and the presence of these antibodies serves as a diagnostic marker for this autoimmune hepatitis type II. We demonstrate that anti-LKM1 IgGs specifically inhibit the hydroxylation of bufuralol in human liver microsomes. Using two assay systems with different selectivity for the two cytochrome P-450 isozymes catalyzing bufuralol metabolism in human liver, we show that anti-LKM1 exclusively recognizes cytochrome P-450db1. Immunopurification of the LKM1 antigen from solubilized human liver microsomes resulted in an electrophoretically homogenous protein that had the same molecular mass (50 kDa) as purified P-450db1 and an identical N-terminal amino acid sequence. Recognition of both purified P-450db1 and the immunoisolated protein on western blots by several monoclonal antibodies confirmed the identity of the LKM1 antigen with cytochrome P-450db1. Cytochrome P-450db1 has been identified as the target of a common genetic polymorphism of drug oxidation. However, the relationship between the polymorphic cytochrome P-450db1 and the appearance of anti-LKM1 autoantibodies as well as their role in the pathogenesis of chronic active hepatitis remains speculative.     

Circulating hepatocyte membrane-specific autoantibodies in chronic active hepatitis type B

Sera from two groups of untreated HBsAG-positive patients with chronic active hepatitis on liver biopsy were tested for antibodies to liver cell membrane antigens (liver-specific protein, LSP; and liver membrane antigen, LM-Ag). Among the 14 HBeAg-positive cases, seven (50%) were positive for anti-LSP, whereas only two (13%) of 15 anti-HBe-positive cases circulated this antibody. Liver membrane autoantibody (LMA) was detected only in two sera from delta-positive patients (1 HBeAg positive and 1 anti-HBe positive). Anti-LSP-positive patients presented transaminase values significantly higher than those of the negative cases. Our data do not support the hypothesis that a liver-specific autoimmune mechanism plays a significant role in the immunopathogenesis of liver cell necrosis in anti-HBe-positive chronic active hepatitis type B. The relationship between hepatocyte necrosis and anti-LSP antibody response is confirmed.     

Detection and further characterization of a newly described microsomal autoantibody associated with chronic delta infection

Sera from 162 patients with acute or chronic hepatitis and from patients with autoimmune diseases have been investigated for autoantibodies by indirect immunofluorescence on human and animal tissues. A small proportion (14.2%) of young patients with chronic delta hepatitis has been found positive for cytoplasmic staining which was maximal in hepatocytes and renal proximal tubules. This autoantibody has been found to react with microsomal antigenic determinant different from the classic liver-kidney microsomal LKM antigen as demonstrated by fluorescence absorption experiments with purified subcellular organelles and by fluorescence-blocking tests. The microsomal autoantibody displayed also organ and species-specificity different from those shown by the LKM-positive sera. The positive patients showed persistence of the microsomal autoantibody during the follow-up without other serological markers of autoimmunity. There was no evidence of a particular course of chronic delta hepatitis in patients positive for the microsomal autoantibody.     

Autoantibodies and defined target autoantigens in autoimmune hepatitis: an overview

Autoimmune hepatitis (AIH) is a disease of unknown aetiology characterised by hypergammaglobulinaemia, non-organ and liver-related autoantibodies, association with HLA-DR3 or DR4 and a favourable response to immunosuppression. The current classification of AIH and the several autoantibodies/target autoantigens found in this disease are reported. The importance of these markers in the differential diagnosis and the study of pathogenesis of AIH is also given. AIH is subdivided into two major types: AIH type 1 (AIH-1) and AIH type 2 (AIH-2). AIH-1 is characterised by the detection of smooth muscle autoantibodies (SMA) and/or antinuclear antibodies (ANA). Antineutrophil cytoplasmic autoantibodies (ANCA), in most cases of perinuclear pattern (p-ANCA), by the indirect immunofluorescence assay, antibodies against the asialoglycoprotein receptor (anti-ASGP-R) and antibodies to soluble liver antigens or liver-pancreas (anti-SLA/LP) may be useful for the identification of individuals who are seronegative for ANA/SMA. AIH-2 is characterised by the presence of specific autoantibodies against liver and kidney microsomal antigens (anti-LKM type 1 or infrequently anti-LKM type 3) and/or autoantibodies against liver cytosol 1 antigen (anti-LC1). Anti-LKM-1 and anti-LKM-3 autoantibodies are also detected in some patients with chronic hepatitis C (HCV) and chronic hepatitis D (HDV). For these reasons, the distinction between AIH and chronic viral hepatitis is of particular importance. Cytochrome P450 2D6 (CYP2D6) is the major target autoantigen of anti-LKM-1 autoantibodies in both conditions (AIH-2 and HCV infection). Recent data have demonstrated the expression of CYP2D6 on the surface of hepatocytes, suggesting a pathogenetic role of anti-LKM-1 autoantibodies in liver injury. Family 1 of UDP-glycuronosyltransferases has been identified as the target autoantigen of anti-LKM-3. The molecular target of anti-SLA/LP autoantibodies has been identified recently as a 50 kDa protein with unknown structure and function. A liver-specific enzyme, the formiminotransferase cyclodeaminase, was identified as the target autoantigen of anti-LC1 autoantibodies. Anti-ASGP-R and anti-LC1 autoantibodies appear to correlate better with the severity of AIH and the response to treatment. The latter may suggest a pathogenic role of these autoantibodies in the hepatocellular damage in AIH. In general, however, autoantibodies should not be used to monitor treatment or to predict AIH activity or outcome. Finally, current knowledge concerning a specific form of AIH that may develop in some patients with a rare genetic syndrome, the autoimmune polyglandular syndrome type-1 (APS-1), is also discussed. Autoantibodies against liver microsomes (anti-LM) are the specific autoantibodies found in AIH as a disease component of APS-1. However, anti-LM autoantibodies have also been described in cases of dihydralazine-induced hepatitis. Cytochrome P450 1A2 has been identified as the target autoantigen of anti-LM autoantibodies in both disease entities.     

Liver membrane antibodies detected by immunoradiometric assay in acute and chronic virus-induced and autoimmune liver disease

In this study, we describe a radioimmunoassay to detect liver membrane binding antibodies. The assay was designed to exclude binding of aggregated IgG or immune complexes to Fc gamma receptors of hepatocytes. When this assay was applied to sera from 142 patients, antibodies were found in highest titer in patients with autoimmune chronic active hepatitis, rarely in patients with hepatitis B virus-induced chronic active liver disease, and in 32% of patients with primary biliary cirrhosis. IgM antibodies were found in 100% of patients with acute Type A but not B or non-A, non-B hepatitis. IgA class antibodies were found in the sera of 57% of patients with alcohol-induced hepatitis. All patient groups showing significant titers of liver membrane antibodies display the lesion of piecemeal necrosis except those with alcohol-induced hepatitis. Further studies are needed to determine whether this antibody is the cause of the lesion.     

Antibodies to alcohol altered liver cell determinants in patients with alcoholic liver disease.

Circulating antibodies reacting specifically with hepatocytes isolated from ethanol pretreated rabbits have been demonstrated by two techniques - induced cytotoxicity and immunofluorescence. In the cytotoxicity assay antibodies were found in seven of 19 (39%) of patients with alcoholic fatty liver (with or without fibrosis), six of 13 (46%) of those with alcoholic hepatitis, 15 of 36 (43%) of those with cirrhosis, and seven of 14 patients (50%) of those with hepatitis and cirrhosis. In the immunofluorescence studies, nine of 15 sera induced a granular pattern of fluorescence on the ethanol pretreated hepatocytes; two sera which induced significant cytotoxicity did not induce immunofluorescence. No ethanol related antibodies were found in normal individuals or in patients with other types of acute or chronic liver disease. These results show that antibodies directed against ethanol altered liver cell determinants are present in the serum of 43% of patients with alcoholic liver disease, and suggest a mechanism whereby chronic alcohol consumption may, by inducing antigenic changes in hepatocyte membranes, trigger a cell damaging immune reaction.     

Antibodies to isolated hepatocytes in chronic active liver disease. Identification and diagnostic significance of bile canalicular antibodies

A branched or net-like immunofluorescence pattern was demonstrated across the surface of isolated rabbit hepatocytes. We presume that this staining pattern is related to bile canaliculi on the cell surface, since it was closely correlated with the presence of bile canalicular antibodies, as detected by immunofluorescence on liver sections. Reaction with the putative bile canaliculi on rabbit hepatocytes was produced by 20 of 26 sera from patients with chronic active liver disease, 13 of 120 sera from patients with various liver diseases, and 1 of 40 normal blood donor sera.     

Hepatocyte plasma membrane antigens. I. Determination of antibodies bound to the hepatocyte plasma membrane by 125I-protein A binding assay

Anti-liver-specific membrane lipoprotein (anti-LP-1) and anti-Tamm-Horsfall glycoprotein (anti-THGP) rabbit antibodies were found to bind to Chang liver cells, a cultured human hepatocyte cell line, and PLC/PRF/5, a hepatoma cell line. The antibodies bound were determined by an immunofluorescence staining and a semiquantitative 125I-protein A binding assay. The 125I-protein A binding assay was successfully adapted to determine anti-hepatocyte plasma membrane antibodies in sera of patients with lupoid hepatitis and chronic active hepatitis. The percentage of 125I-protein A bound in 10 normal subjects were 1.5 +/- 0.4 (mean +/- standard deviation) for PLC/PRF/5 and 1.6 +/- 0.6 for Chang liver cell, while those in 2 patients with lupoid hepatitis were 7.2 +/- 0.3, 5.9 +/- 0.1, and those in 8 patients with chronic active hepatitis 3.9 +/- 1.3, 3.2 +/- 1.5, respectively. Furthermore, a blocking study revealed that LP-1 and THGP were partially involved in antigen sites recognized with anti-hepatocyte plasma membrane antibodies in sera of a patient with lupoid hepatitis. The retaining ability of antibody binding to the hepatocytes after the absorption with non-hepatocyte cells suggested the presence of antibodies specific for the hepatocyte plasma membrane in the patient's serum.     

Chronic active hepatitis associated with anti-liver-kidney microsome antibody type 1

A 3 years old girl presented with clinical feature of an acute hepatitis-like illness, with jaundice, hepatosplenomegaly, high alanine aminotransferase activity (ALT) and high gamma-globulin values. We were able to demonstrate high titre of anti-liver-kidney microsome antibodies type 1 (LKMA1) in the serum of this patient using immunofluorescence, ELISA (Enzyme-linked immunoabsorbent assay) and Western blot (WB) analysis. This observation together with the liver morphology and after excluding other possible causes of hepatitis established the diagnosis of chronic active hepatitis associated with anti-LKM1 antibody. Immunosuppressive therapy was therefore started immediately.     

Features and outcome of autoimmune hepatitis type 2 presenting with isolated positivity for anti-liver cytosol antibody.

BACKGROUND AND AIMS: Autoimmune hepatitis (AIH) type 2 is identified by the presence in the serum of anti-liver/kidney microsome type 1 autoantibody. Anti-liver cytosol autoantibody has been reported in children with autoimmune liver disorders mostly in association with anti-liver/kidney microsome reactivity. However, its role as a sole marker of AIH type 2 is debated. We describe here a series of 18 children and adolescents (15 girls, 3 boys) with AIH with serum anti-liver cytosol type 1 (aLC1) as the only autoimmune marker. METHODS: A retrospective review was conducted from 3 pediatric hepatology units of all children with an autoimmune liver disease associated with aLC1 as found by immunofluorescence and/or immunodiffusion or immunoblotting. RESULTS: Age at first symptoms ranged from 11 months to 14 years; 12 children presented with acute hepatitis, 1 with progressive jaundice, and 5 were asymptomatic. Anti-liver/kidney microsome, antimitochondria, and anti-actin autoantibodies were not detected. Signs of cirrhosis were present in 11 children. Immunosuppressive treatment was effective in all except 2 children who had subfulminant hepatic failure and who required liver transplantation. Sixteen patients (14 with their native liver) currently are alive; 14 patients still are on immunosuppressive therapy after 1 to 22 years. According to the international scoring system for the diagnosis of AIH, 16 patients corresponded to a definite diagnosis and 2 corresponded to a probable diagnosis. CONCLUSIONS: The presence of aLC1 in children with acute or chronic liver disease of unknown origin strongly supports a diagnosis of AIH and is an indication for early immunosuppressive therapy.     

Human anti-endoplasmic reticulum autoantibodies appearing in a drug-induced hepatitis are directed against a human liver cytochrome P-450 that hydroxylates the drug.

"Anti-liver/kidney microsome" (anti-LKM) autoantibodies have been found in the serum of patients with cryptogenic chronic hepatitis and with immunoallergic drug-induced hepatitis, such as those induced by halothane or by tienilic acid (called anti-LKM2 in this case). So far the nature of the human microsomal macromolecules recognized by these antibodies has not been determined. Here we show, by using immunoblot techniques, that among the macromolecules present in human adult liver microsomes, one protein called cytochrome P-450-8 is specifically recognized by most sera of patients containing anti-LKM2 antibodies but not by control serum. Human fetal liver microsomes that do not contain cytochrome P-450-8 are not recognized by the anti-LKM2 antibodies. It is also shown that anti-cytochrome P-450-8 antibodies as well as human serum containing anti-LKM2 antibodies specifically inhibit the hydroxylation of tienilic acid by human liver microsomes. These results indicate that anti-LKM2 antibodies appearing in patients with hepatitis and concomitant administration of tienilic acid are directed against a cytochrome P-450 isoenzyme that catalyzes the metabolic oxidation of this drug. This suggests a possible mechanism for the appearance of anti-organelle antibodies in a drug-induced hepatitis.