M2抗体人源靶抗原三联体的克隆表达及其在原发性胆汁性肝硬化中的应用

目的 设计克隆表达抗原蛋白三联体BPO，利用纯化的重组BPO，建立原发性胆汁性肝硬化(primary biliary cirrhosis，PBC)特异性免疫学诊断方法。方法 利用基因工程方法克隆表达M2抗原及其三联体BP0，并加以鉴定。纯化BPO，建立ELISA法。应用ELISA法检测17例PBC患血清M2抗体，以167例非PBC患和1225例健康人作对照。结果 17例临床诊断为PBC的患，M2抗体均为阳性，而对照组M2抗体均为阴性。结论 本法检测M2抗体有较好的敏感性及特异性，为PBC的临床诊断提供了有效手段。     

用ELISA检测抗丙酮酸脱氢酶复合物E2和E3结合蛋白自身抗体

目的　用重组丙酮酸脱氢酶复合物E2亚单位和E3结合蛋白 (PDC E2 ,PDC E3BP)建立筛查原发性胆汁性肝硬化 (PBC)患者相应自身抗体的ELISA。方法　用本室制备的重组PDC E2和PDC E3BP蛋白包被酶联反应板 ,检测PBC患者、正常人及其他肝病患者血清。结果　组建成筛查PBC患者血清中自身抗体的试剂盒 ,能够准确地检测PBC患者血清中的自身抗体。结论　建立的试剂盒能用于PBC患者血清中丙酮酸脱氢酶复合物自身抗体的检测。     

Serial changes in enzyme inhibitory antibody to pyruvate dehydrogenase complex during the course of primary biliary cirrhosis

To assess the usefulness of enzyme inhibition assay for the diagnosis of primary biliary cirrhosis (PBC), we determined the serial changes in enzymatic inhibitory antibody to pyruvate dehydrogenase complex (PDC) in patients with PBC, and compared the results to those of immunofluorescence and immunoblotting. Forty-nine sera from 19 patients with PBC who were followed-up for at least 16 months were tested for antimitochondrial antibodies (AMA) by indirect immunofluorescence, immunoblotting on bovine heart mitochondria, and enzyme inhibition assay using commercially available TRACE Enzymatic Mitochondrial Antibody (M2) Assay (EMA) kit. Of the 49 sera, 39 (80%), 35 (71%), 38 (78%), 31 (63%), and 36 (73%) were positive for AMA by immunofluorescence, for immunoglobulin G (IgG), IgM, and IgA class antibody against E2 subunit of PDC (PDC-E2) by immunoblotting, and for enzymatic inhibitory antibody to PDC by EMA, respectively. AMA titers determined by immunofluorescence did not change in 9 patients (47%), increased in 4 (21%), decreased in 3 (16%), and fluctuated in 3 (16%) during follow-up. The number of anti-M2 bands by immunoblotting did not change in 9 (47%), increased in 6 (32%), decreased in 2 (11%), and fluctuated in 2 (11%). Units of PDC activity by EMA did not change markedly in 16 (84%), increased in 2 (11%), and fluctuated in 1 (5%). Positive EMA results were common in cases with high levels of serum alkaline phosphatase and IgM, and the units of PDC activity by EMA correlated significantly and inversely with AMA titers by immunofluorescence, and serum reactivity to PDC-E2 by immunoblotting, respectively. There was no correlation between serial changes in biochemical data and units of PDC activity by EMA. In three patients who showed a decrease in AMA titers, AMA titers correlated more with EMA results than immunoblotting. Moreover, in a patient with fluctuating AMA titers, the units of PDC activity by EMA paralleled AMA titers. Our results suggest that EMA is useful for the diagnosis of AMA-positive PBC, and also could be used for monitoring the disease course in PBC.     

A contemporary perspective on the molecular characteristics of mitochondrial autoantigens and diagnosis in primary biliary cholangitis

Primary biliary cholangitis (PBC) is an autoimmune hepatobiliary disease characterized by immune mediated destruction of the intrahepatic small bile ducts and the presence of antimitochondrial antibodies (AMAs). The mitochondrial autoantigens have been identified as the E2 subunits of the 2-oxo-acid dehydrogenase complex, including the E2 subunits of pyruvate dehydrogenase, branched-chain 2-oxo acid dehydrogenase complex, oxoglutarate dehydrogenase complex, E3 binding protein and PDC E1 alpha subunit. The AMA epitope is mapped within the E2 lipoic acid binding domain, which is particularly important for oxidative phosphorylation. In addition, lipoic acid, which serves as a swinging arm to capture electrons, is particularly susceptible to an electrophilic attack and may provide clues to the etiology of PBC. This review emphasizes the molecular characteristics of AMAs, including detection, immunochemistry and the putative role in disease. These data have significance not only specifically for PBC, but generically for autoimmunity.     

Evaluation of newly developed ELISA using "MESACUP-2 test mitochondrial M2" kit for the diagnosis of primary biliary cirrhosis

OBJECTIVES: An enzyme-linked immunosorbent assay (ELISA) using MESACUP-2 Test Mitochondria M2 kit (new-M2 ELISA) has recently become commercially available. The aim of this study was to evaluate the clinical utility of this newly developed ELISA for the diagnosis of primary biliary cirrhosis (PBC). DESIGN AND METHODS: We tested the immunoreactivity of sera from 82 Japanese PBC patients to the 2-oxo-acid dehydrogenase complex (2-OADC) enzymes by indirect immunofluorescence, enzyme inhibition assay using commercially available TRACE Enzymatic Mitochondrial Antibody (M2) Assay (EMA) kit, commercial ELISAs using MESACUP Mitochondria M2 kit (old-M2 ELISA) and new-M2 ELISA, and immunoblotting on bovine heart mitochondria. RESULTS: Each test gave the following positive results; antimitochondrial antibodies (AMA) by immunofluorescence in 71 (87%) out of the 82 sera, enzymatic inhibitory antibody to pyruvate dehydrogenase complex (PDC) by EMA in 61 (74%), immunoglobulin (Ig) G class anti-PDC antibody by old-M2 ELISA in 55 (67%), IgG/M/A class anti-E2 subunit of PDC (PDC-E2)/anti-E2 subunit of branched chain oxo-acid dehydrogenase complex (BCOADC-E2)/anti-E2 subunit of 2-oxoglutarate dehydrogenase complex (OGDC-E2) antibodies by new-M2 ELISA in 73 (89%), and IgG, IgM, or IgA class antibodies against at least one of the 2-OADC enzymes by immunoblotting in 82 (100%). Fifty-three of the 82 sera (65%) were all positive by these five assays. Of the 18 sera that were positive by new-M2 ELISA but negative by old-M2 ELISA, 12 were theoretically interpretable. Of the 11 sera that were negative for AMA by immunofluorescence but positive for at least one of anti-2-OADC enzymes by immunoblotting, four (36%) were positive by new-M2 ELISA, whereas only two and one sera were positive by EMA and old-M2 ELISA, respectively. CONCLUSIONS: Our results indicated that the sensitivity of the newly developed new-M2 ELISA was higher than that of EMA and old-M2 ELISA, and comparable with that of immunofluorescence. However, it is still unclear whether the new-M2 ELISA could replace the conventional immunofluorescence testing for routine assay requests because six (7%) sera showed discrepant results between these two assays.     

Heterogeneity of autoreactive T cell clones specific for the E2 component of the pyruvate dehydrogenase complex in primary biliary cirrhosis

The extraordinary specificity of bile duct destruction in primary biliary cirrhosis (PBC) and the presence of T cell infiltrates in the portal tracts have suggested that biliary epithelial cells are the targets of an autoimmune response. The immunodominant antimitochondrial response in patients with PBC is directed against the E2 component of pyruvate dehydrogenase (PDC-E2). Hitherto, there have only been limited reports on the characterization and V beta usage of PDC-E2-specific cloned T cell lines. In this study, we examined peripheral blood mononuclear cells (PBMC) for their reactivity to the entire PDC complex as well as to the E1- and E2-specific components. We also examined the phenotype, lymphokine profile, and V beta usage of PDC-specific T cell clones isolated from cellular infiltrates from the livers of PBC patients. We report that PBMC from 16/19 patients with PBC, but not 12 control patients, respond to the PDC-E2 subunit. Interestingly, this response was directed to the inner and/or the outer lipoyl domains, despite the serologic observation that the autoantibody response is directed predominantly to the inner lipoyl domain. Additionally, lymphokine analysis of interleukin (IL) 2/IL-4/interferon gamma production from individual liver-derived autoantigen-specific T cell clones suggests that both T helper cell Th1- and Th2-like clones are present in the liver. Moreover, there was considerable heterogeneity in the T cell receptor for antigen (TCR) V beta usage of these antigen- specific autoreactive T cell clones. This is in contrast to murine studies in which animals are induced to develop autoimmunity by specific immunization and have an extremely limited T cell V beta repertoire. Thus, our data suggest that in human organ-specific autoimmune diseases, such as PBC, the TCR V beta repertoire is heterogenous.     

Molecular and biochemical basis of intermediate maple syrup urine disease. Occurrence of homozygous G245R and F364C mutations at the E1 alpha locus of Hispanic-Mexican patients.

Maple syrup urine disease (MSUD) is caused by a deficiency of the mitochondrial branched-chain alpha-keta acid dehydrogenase (BCKAD) complex. The multienzyme complex comprises five enzyme components, including the E1 decarboxylase with a heterotetrameric (alpha 2 beta 2) structure. Four unrelated Hispanic-Mexican MSUD patients with the intermediate clinical phenotype were diagnosed 7 to 22 mo after birth during evaluation for developmental delay. Three of the four patients were found homozygous for G to A transition at base 895 (exon 7) of the E1 alpha locus, which changes Gly-245 to Arg (G245R) in that subunit. The remaining patient was homozygous for T to G transversion at base 1,253 in the E1 alpha gene, which converts Phe-364 to Cys (F364C) in the gene product. Transfection studies in E1 alpha-deficient lymphoblasts indicate that both G245R and F364C mutant E1 alpha subunits were unable to significantly reconstitute BCKAD activity. Western blotting showed that both mutant E1 alpha subunits in transfected cells failed to efficiently rescue the normal E1 beta through assembly. The putative assembly defect was confirmed by pulse-chase labeling of E1 subunits in a chaperone-augmented bacterial overexpression system. The kinetics of initial assembly of the G245R E1 alpha subunit with the normal E1 beta was shown to be slower than the normal E1 alpha. No detectable assembly of the F364C E1 alpha with normal E1 beta was observed during the 2 h chase. Small amounts of recombinant mutant E1 proteins were produced after 15 h induction with isopropyl thiogalactoside and exhibited very low or no E1 activity. Our study establishes that G245R and F364C mutations in the E1 alpha subunit disrupt both the E1 heterotetrameric assembly and function of the BCKAD complex. Moreover, the results suggest that the G245R mutant E1 alpha allele may be important in the Hispanic-Mexican population.     

Peripheral blood T-cell responses to pyruvate dehydrogenase complex in primary biliary cirrhosis: role of antigen-presenting dendritic cells

Patients with primary biliary cirrhosis (PBC) are usually characterized by the presence of antibody to pyruvate dehydrogenase complex (PDC) in the sera and PDC-specific T cells in the liver. However, most of the patients with PBC do not show peripheral blood T cells response to PDC. In this study, we re-evaluated the peripheral blood T cell responses to PDC in PBC using antigen-presenting dendritic cells (DCs). Twenty-four patients with PBC (AMA-positive: 16; AMA-negative: 8) and 13 normal controls were enrolled in the study. Peripheral blood mononuclear cells (PBMC) and highly enriched populations of T cells were stimulated with either only PDC or DCs plus PDC or PDC-pulsed DC plus PDC. Antibodies to different components of PDC were estimated by an immunoblotting technique. PBMC from only one out of ten AMA-positive PBC patients proliferated when cultured with only PDC. However, peripheral blood T cells from ten out of ten AMA-positive PBC patients and three out of ten AMA-negative PBC patients, but none of the five normal controls showed PDC-specific proliferation when cultured with PDC-pulsed DCs. Two of these three AMA-negative PBC patients, although negative for AMA, were positive for antibodies to other components of PDC. PDC-specific T cells are present in the peripheral blood from most of the patients with PBC. This is the first report on the effectiveness of antigen-pulsed DCs for the elucidation of autoantigen-specific immune response in human autoimmune diseases.     

用重组M2三联体抗原建立原发性胆汁性肝硬化免疫检测法

目的 建立原发性胆汁性肝硬化（PBC）特异性免疫学检测方法。方法 在重组质粒表达的基础上，用亲和层析进一步纯化重组蛋白后，用酶免疫吸附法检测M2抗体。结果 在PBC组11例患者哈部检出M2抗体，阳性率为1005，而非PBC组75例患者中无一检出M2抗体，本法与病理检查和临床诊断的相关性有非常显著意义（P＜0.01）。结论 本法检测M2抗体有较好的敏感性及特异性，为PBC的早期发现和临床诊断提供了有力的工具。     

用重组丙酮酸脱氢酶复合物E2亚单位检测M2抗体及其临床意义

目的用重组表达的丙酮酸脱氢酶复合物E2亚单位(PDC-E2)检测M2抗体,以利于原发性胆汁性肝硬化(PBC)的早期诊断。方法采用重组表达的PDC-E2建立了免疫印迹法(IBT)和酶联免疫吸附试验(ELISA)。检测40例PBC患者血清的M2抗体,以其他肝病患者、自身免疫病患者、健康体检者作对照。结果40例PBC患者血清中检测出抗PDC-E2抗体阳性37例,阴性3例,阳性率为92.5%,而疾病对照组和健康体检者血清中该抗体检测均为阴性。结论用重组表达的人PDC-E2检测抗体有较好的敏感性和特异性,有助于PBC的临床诊断。     

Incidence of a split alpha 2-glycoprotein band in the electrophoretic pattern for serum of adenocarcinoma patients

We electrophoresed serum samples on Mylar-backed cellulose acetate membranes and stained for glycoproteins with the periodic acid--Schiff reagent. The samples were from untreated adenocarcinoma patients, adenocarcinoma patients receiving chemotherapy, and patients with other malignancies, and also from patients with benign proliferative diseases, inflammatory diseases, and other non-malignant conditions. Forty-five per cent of the sera from untreated adenocarcinoma patients and 80% of those from adenocarcinoma patients with progressive systemic disease exhibited a splitting of the alpha 2-glycoproteins into a fast and slow band. Such a pattern was seen in only 4% of the non-adenocarcinoma cancer patients and 4% of the control group. Serial studies indicated that electrophoretic patterns of alpha 2-glycoproteins change with clinical status. Non-cancer patients with high concentrations of acute-phase proteins in their serum did not exhibit two alpha 2-glycoprotein bands. Further characterization of serum proteins from the fast alpha 2 region suggest that alpha 1-acid glycoprotein and haptoglobin beta chains are the principal components staining with periodic acid--Schiff reagent. These components are markedly less apparent in, or are absent from, the fast alpha 2 region of normal sera.     

Detection of autoantibodies against M2, LKM-1, and SLA in liver diseases by standardized uniform ELISA-techniques

Antibodies directed against soluble liver antigen (SLA), liver kidney microsomal antigen (LKM-1-AG), and antimitochondrial antigen M2 (M2-AMA) are critical serological markers for the differential diagnosis of autoimmune chronic active hepatitis (AI-CAH) and primary biliary cirrhosis (PBC). The exact diagnosis of autoimmune hepatitis and PBC is of great clinical relevance, as it leads to different therapeutic strategies. In the present work, a simple and reliable ELISA test system is described, which applies the same test principle for the detection of three different species of autoantibodies important for the diagnosis of chronic liver disease. The ELISA assays are based on a competitive inhibition of binding of positive standard antibodies by patients sera containing antibodies of unknown specificity. The purified immunoglobulins of clinically and serologically clearly defined patients with SLA or LKM-1 positive AI-CAH and with M2 positive PBC were used as coating- and detection antibodies in the ELISAs. From homogenized rat liver the fractionated 100,000g supernatant was employed for the SLA ELISA, the microsomal preparation served as antigen for the LKM-1 ELISA and the mitochondrial preparation was used for the M2 ELISA. In 1,500 sera of patients with the differential diagnosis of a hepatobiliary disease, 17 gave a positive signal in the SLA ELISA, 12 in the LKM-1-ELISA, and 72 in the M2-ELISA. The results of the ELISAs were compared with Western blotting and immunofluorescence staining pattern on cryostat sections and Hep2 cells. The antibody profiles of several patients are described in detail. © 1994 Wiley-Liss, Inc.     

Inherited deficiency of the Mac-1, LFA-1, p150,95 glycoprotein family and its molecular basis

Leukocyte surface glycoproteins that share a common beta subunit have been found to be congenitally deficient in three unrelated patients with recurring bacterial infection. The glycoproteins, Mac-1, LFA-1, and p150,95, have the subunit compositions alpha M beta, alpha L beta, and alpha X beta, respectively. Using subunit-specific monoclonal antibodies, both the alpha M and beta subunits of Mac-1, the alpha L and beta subunits of LFA-1, and at the least the beta subunit of p150,95, were found to be deficient at the cell surface by the techniques of immunofluorescence flow cytometry, radioimmunoassay, and immunoprecipitation. A latent pool of Mac-1 that can be expressed on granulocyte surfaces in response to secretory stimuli, such as f-Met- Leu-Phe, was also lacking in patients. Deficiency was found on all leukocytes tested, including granulocytes, monocytes, and T and B lymphocytes. Quantitation by immunofluorescence cytometry of subunits on granulocytes from parents of these patients and of a fourth deceased patient showed approximately half-normal surface expression, and, together with data on other siblings and a family with an affected father and children, demonstrate autosomal recessive inheritance. Deficiency appears to be quantitative rather than qualitative, with two patients expressing approximately 0.5% and one patient approximately 5% of normal amounts. The latter patient had alpha beta complexes on the cell surface detectable by immunoprecipitation. Biosynthesis experiments showed the presence of normal amounts of alpha'L intracellular precursor in lymphoid lines of all three patients. Together with surface deficiency of three molecules that share a common beta subunit but have differing alpha subunits, this suggests the primary deficiency is of the beta subunit. The lack of maturation of alpha'L to alpha L and the deficiency of the alpha subunits at the cell surface and in latent pools suggests that association with the beta subunit is required for alpha subunit processing and transport to the cell surface or to latent pools. The molecular basis of this disease is discussed in light of adhesion-related functional abnormalities in patients' leukocytes and the blockade of similar functions in healthy cells by monoclonal antibodies.     

High-molecular intestinal alkaline phosphatase in chronic liver diseases

The presence of high-molecular intestinal alkaline phosphatase (HIALP) different from bone ALP detected in the alpha(2)beta region was recently clarified. In this study we used a novel method in which HIALP was detected after conversion to ALP(5) by protease to investigate the clinical significance of the appearance of HIALP in patients with chronic liver disease. The subjects were 241 patients with chronic liver disease. When a decrease in ALP(3) in the alpha(2)beta region and an increase in ALP(5) in the beta region were noted, the patient was judged HIALP-positive. In the patients with chronic liver disease, the total ALP activity (T-ALP) increased with progression of the pathology in the order of chronic hepatitis (CH), liver cirrhosis (LC), and hepatocellular carcinoma (HCC). HIALP appeared in 22.4% and 49.3% of patients with CH and LC, respectively, but the positivity rate decreased to 30.4% in HCC. As autoimmune liver diseases, primary biliary cirrhosis (PBC) and autoimmune hepatitis (AIH) were investigated. T-ALP was lower in PBC+AIH than in LC and HCC, but the HIALP-positive rate was high (44.4%). The HIALP-positive rate was dependent on ABO blood groups, and was high in blood groups B and O. In conclusion, the HIALP-positive rate was particularly high in patients with chronic liver disease, and was related to the pathological progression, which suggests that the method is clinically useful.     

原发性胆汁性肝硬化自身抗体谱的检测及临床应用

目的 探讨联合检测多种自身抗体在原发性胆汁性肝硬化(PBC)诊断中的价值及临床意义.方法 用免疫印迹法分别检测96例PBC患者,100例其他自身免疫性疾病(AID)患者和49名健康体检者血清中的抗线粒体(AMA)-M2亚型抗体、抗3E(BPO)抗体、抗Sp100抗体、抗旱幼粒细胞性白血病(PML)抗体、抗gp210抗体、抗肝肾微粒体-1(LKM-1)抗体、抗肝特异性胞质抗体-1(LC-1)、抗可溶性肝抗原/肝胰抗原抗体(SLA/LP).结果 96例PBC患者中AMA-M2、抗3E(BPO)抗体、抗Sp100抗体、抗PML抗体、抗gp210抗体阳性率分别为76.0%、84.4%、32.3%、28.1%、35.4%,而以上5种自身抗体在其他自身免疫性疾病中的阳性率分别为13.0%、9.0%、3.0%、2.0%、1.0%;AMA-M2对PBC诊断的敏感度达76.0%,特异度达87.0%;抗3E(BPO)抗体对PBC诊断的敏感度达84.4%,特异度达91.0%;抗Sp100抗体对PBC诊断的敏感度达32.3%,特异度达97.0%;抗PML抗体对PBC诊断的敏感度达28.1%,特异度达98.%;抗gp210抗体对PBC诊断的敏感度达35.4%,特异度达99.0%,未检测到抗LKM-1抗体、抗LC-1抗体及抗SLA/LP抗体;抗gp210抗体阳性患者肝功能衰竭的发生率明显高于抗体阴性患者(χ2 =11.17,P<0.01).结论 PBC患者中可检测到多种自身抗体,自身免疫性肝病自身抗体谱检测对PBC诊断、鉴别诊断、治疗及预后判断均有重要意义.     

M2抗体重组人源靶抗原二联体在原发性胆汁性肝硬化患者中的检测及应用

目的 利用重组抗原BCOADA-E2和PDC-E2的二联体（BP），检测PBC患者血清中的M2抗体并探讨其临床意义。方法 经Ni—NTA亲和柱纯化重组表达的BP融合蛋白，分别建立免疫印迹法（IBT）和酶链免疫吸附（ELISA）法检测60份PBC患者血清，以60份其他肝病患者、60份自身免疫病患者、80例正常人血清为对照组。结果 经常规试剂盒检测为M2（＋）的60份患者血清，利用重组抗原检测阳性53例，阴性7例，阳性率为88．3％；经常规试剂盒检测为M2（-）的60份自身免疫病患者血清、60份其他肝病患者和80例正常人血清，利用重组抗原检测为M2（-）。结论 利用重组抗原BP检测M2抗体敏感性较高。对临床辅助诊断PBC提供一定的手段。     

Free alpha-subunit, free beta-subunit of human chorionic gonadotropin (hCG), and intact hCG in sera of healthy individuals and testicular cancer patients.

To determine the serum concentrations of human chorionic gonadotropin (hCG), its free beta-subunit (hCG beta), and the free alpha-subunit (free alpha) common to all human glycoprotein hormones under physiological and pathological conditions, we developed monoclonal antibody-based immunoenzymometric assays. Free alpha-subunit was detected in the sera of all healthy individuals of both sexes; hCG was measurable in sera of 54% of the men, and 46% were positive for free hCG beta; in nonpregnant women, 69.5% were positive for hCG, 68.4% for the free beta-subunit. Pathological conditions, i.e., hCG-producing tumors, were studied in vitro and in vivo. In vitro, the concentrations of hCG, free hCG beta, and free alpha in tissue-culture supernates of a choriocarcinoma cell-line ("JAR") showed a parallel pattern during time-course analysis. In vivo, in long-term follow-up studies of 13 patients with testicular cancer, serum concentrations of the three analytes paralleled each other, whether the disease was in remission or not. Because of a selective increase of free hCG beta and free alpha in 27% of seminomatous tumor patients and in 13% of the nonseminomatous patients, the percentage of tumor-marker-positive sera was increased from 15% to 42% and 57% to 70%, respectively, by the additional measurement of free hCG beta and free alpha. Thus hCG, free hCG beta, and free alpha are physiologically present in a high percentage of the sera from healthy men, and the determination of free hCG beta and free alpha, although not of prognostic value, improves the diagnostic possibilities in patients with testicular cancer.     

以合成肽作抗原的酶联免疫吸附法诊断戊型肝炎病毒感染

建立了用合成多肽抗原测定戊型肝炎病毒（ＨＥＶ）抗体的酶联免疫吸附法。合成多肽Ｅ３３（ｃ）（２μｇ／ｍｌ）、Ｅ１５（Ｍ）（１μｇ／ｍｌ）混合包被，测定了４８份ＨＥＶ抗体阳性血清，阳性符合率为９５．８％。４１份阴性血清均为阴性。此方法灵敏度高、特异性强、简便快速，适合临床应用。     

Quantification of cleaved beta2-microglobulin in serum from patients undergoing chronic hemodialysis

BACKGROUND: Patients on chronic hemodialysis are prone to develop amyloid deposits of misfolded beta(2)-microglobulin (beta(2)M) in osteoarticular tissues. beta(2)M with various deletions/truncations and chemical modifications has been found together with structurally intact beta(2)M in extracts of beta(2)M amyloid fibrils. The state of the circulating population of beta(2)M molecules has not been characterized previously with high-resolution methods. METHODS: We used immunoaffinity-liquid chromatography-mass spectrometry analysis of serum samples to examine whether structurally modified beta(2)M is generated in the circulation. In addition, we developed an immunoassay for the quantification of a cleaved beta(2)M variant in biological fluids based on novel monoclonal antibodies and applied this assay to patient and control sera. RESULTS: A specific alteration compatible with the generation of lysine-58-cleaved and truncated beta(2)M (DeltaK58-beta(2)M) was found in the sera of many (20%-40%) dialysis patients but not in control sera or sera from patients with cerebral amyloidosis (Alzheimer disease). Applied to patient sera, specific immunoassays revealed that dialysis, as expected, significantly lowered the total beta(2)M concentration, but the concentrations of DeltaK58-beta(2)M remained unchanged after dialysis. The results also show that patients dialyzed with less biocompatible membranes have higher serum concentrations of cleaved beta(2)M (mean, 8.5, 1.8, and 0.7 mg/L in cuprophane membrane-dialyzed, polysulfone membrane-dialyzed, and control sera, respectively). CONCLUSIONS: This study for the first time demonstrates and assigns the structure of a specific beta(2)M variant in sera from dialysis patients. Because this variant is conformationally unstable in vitro, it may be involved in in vivo amyloidogenesis.     

Studies of Cryoproteins in Systemic Lupus Erythematosus

Cryoproteins observed in patients with systemic lupus erythematosus were shown to be of "mixed type," consisting largely of IgG and IgM. The IgM moiety possessed anti-IgG globulin reactivity and precipitated in the cold after mixing with a source of IgG. The IgM fraction of one cryoprotein precipitated only with the same patient's IgG. Antisera prepared against purified cryoproteins regularly recognized IgM, IgG, the 11 S component of C', and alpha(2)-macroglobulin. C'4 (beta(1E)) and C'3 (beta(1C)) were recognized by four and two antisera, respectively. Antisera prepared against two cryoproteins reacted (after absorption) only with the sera of origin. These "unique" antigens were associated with IgM, were destroyed by mercaptoethanol treatment, and, in one patient, were shown to disappear subsequent to clinical improvement.