Lactate dehydrogenase isoenzyme(s) linked to IgA immunoglobulin in a patient with a myocardial infarction

Electrophoretic analysis of enzyme-linked immunoglobulins and their clinical significance

The appearance of circulating enzyme-linked immunoglobulin complexes (E-Ig) is common for most enzymes used in clinical biochemical tests. The presence of E-Ig may result in altered enzyme activity in serum and interfere with the measurement of isoenzymes, and is thus of diagnostic importance. E-Ig can be identified by confirming that the binding protein is an immunoglobulin by its reaction with specific anti-human immunoglobulin antibodies. Currently, the presence of E-Ig in an individual is regarded as a benign phenomenon, not indicative of any particular disease process. However, it is becoming clear that E-IgG are closely associated with autoimmune states.

Mitochondrial aspartate aminotransferase linked to immunoglobulin G of the kappa-lambda type: report of a case

Macromolecular aspartate aminotransferase (L-aspartate: 2-oxoglutarate aminotransferase EC 2.6.1.1, AST) was found in the serum of a patient with benign hypertension. The serum total AST and mitochondrial AST (mAST) activities were proportionately higher. The abnormal AST was found to be a macromolecular complex composed of mAST and immunoglobulin G of the kappa-lambda type. The dissociated IgG from the complex was shown to combine with human and rat mAST, but not with cytosolic AST of both species. Molecular mass of the macromolecular AST was estimated to be 360,000 Da. These results indicate that the complex may consist of one IgG molecule associated with two mAST molecules. By the method of papain digestion the binding site of immunoglobulin in the complex appeared to be located in the Fab portion of the IgG molecule. This finding strongly suggests that the AST-immunoglobulin complex is a specific antigen-antibody complex.

An immunoglobulin G inhibiting lactate dehydrogenase activity

We found extremely low (6 U/l) serum lactate dehydrogenase (LDH, EC 1.1.1.27) activity in a patient with uterine myoma. The patient's serum inhibited purified LDH isoenzymes. One milliliter serum neutralized 73 U purified LDH-1 isoenzyme, equivalent to 300-500-fold the amount of LDH in 1 ml of normal serum. The serum inhibitor was purified by ordinary procedures using chromatographies and identified as IgG which contains both kappa- and lambda-chains. The IgG is very unique in showing higher affinity to the H- than M-subunit of the LDH tetramer, in contrast with the IgGs already reported. After removal of the myoma, the anti-LDH activity gradually decreased with a half-life of 20 days corresponding to that of IgG and finally almost disappeared. This indicates a possibility that the myoma cells produce some factors such as B-cell growth and differentiation factors.

Occurrence of two forms of H2M2 isoenzyme of lactate dehydrogenase

Serum from healthy human subjects and serum from animals demonstrated a splitting of the H2M2 isoenzyme fraction of lactate dehydrogenase (LDH) into two subbands on polyacrylamide gel electrophoresis. These subbands were designated H2M2-a and H2M2-b, based on their relative electrophoretic mobilities, with the H2M2-a band being more anodal. The doublet of the H2M2 band was also demonstrated in human erythrocytes and in the hybridization mixture from porcine LDH, indicating the production of two forms of H2M2 isoenzyme in tissues. Supportive evidence for the presence of two H2M2 subforms was obtained by ion-exchange chromatography of the hybridization mixture. The recombination experiments of LDH-binding IgA with both normal human serum and LDH M subunit variant serum indicated the difference of molecular structure between the two subforms. On the basis of the results obtained in this study, a theoretical model of the probable molecular structure of LDH isoenzymes is proposed which could account for both the occurrence of two subforms of H2M2 and their selective binding to LDH-linking IgA.

Antibody interference with biochemical tests and its clinical significance

Antibody interference with routine biochemical tests is becoming increasingly recognized as a cause of spurious results. It is important to recognize these interferences because inappropriate investigation may be instituted in response to the abnormal test result. The present review deals with the various biochemical tests in which antibody interference occurs. The tests include measurement of enzymes, hormones, immunoglobulins, vitamin B12, and a variety of other molecules and ions.

Membrane associated enzyme complexes containing lambda type immunoglobulin A

The properties of the membrane associated enzyme complexes were investigated. The enzyme complexes of alkaline phosphatase, arylamidase, and L-gamma-glutamyltranspeptidase were excluded by gel filtration on Sephadex G-200. The electrophoretic mobility of the enzyme complexes was found to be in the alpha-1 portion and these enzyme activities were immunologically fixed by anti-IgA and anti-light chain lambda antibodies. Heterogeneity in density was observed by density gradient ultracentrifugation. The activities of membrane-associated enzymes were demonstrated in both high (d > 1.21) and low density particles (1.063 < d < 1.21), and the enzyme activities of a high density particle were immunologically fixed by anti-IgA and anti-light chain lambda antibodies. The heterogeneity in density was based on the presence of immunoglobulin A molecule in the complexes. The specificity of the immunoglobulin which was found in the enzyme complexes proved to be exclusively of the alpha heavy chain classes and lambda light chain types respectively. This isotype specificity of immunoglobulin A is similar to the specificity observed in enzyme-linked immunoglobulins, and simple non-specific binding of immunoglobulin and membrane moiety was eliminated. This isotype specificity is of interest in connection with the properties of the circulating autoantibodies.

Malabsorption and macroamylasemia. Response to gluten withdrawal

A 36 year old woman presented with malabsorption and macroamylasemia. The macroamylase was characterized and shown to be a complex of pancreatic amylase and immunoglobulin A(IgA). The patient had the clinical and histologic features of adult celiac disease, and responded to a gluten-free diet. The macroamylase complex disappeared from the serum after gluten withdrawal, a hitherto unreported finding in the syndrome of malabsorption and hyperamylasemia.

An abnormal macro lactate dehydrogenase isoenzyme not due to immunologlobulin binding

We report here on the lactate dehydrogenase (LD) of a patient who presented with an additional LD isoenzyme band between LD 3 and LD4 found during routine examination. The abnormal LD was found to be of increased molecular size, which was not due to complexing with immunoglobulins. The abnormal LD was purified by affinity chromatography, labelled and electrophoresed on a SDS-polyacrylamide gel. Autoradiography suggested abnormal aggregation as the cause of increased molecular size.

Demonstration of antibody for glutamic pyruvic transaminase (GPT) in chronic hepatic disorders

The present paper describes the detection of an autoantibody for glutamic pyruvic transaminase (GPT) in sera of patients with chronic hepatic disorders. In 16 out of 500 patients, the existence of an antibody for pig GPT was demonstrated by the double antibody method, gel filtration and radioimmunoelectrophoresis. The antibody was demonstrated as an immunoglobulin G (IgG) with either polyclonal or monoclonal type (kappa or lambda). The binding portion of IgG with GPT was determined as the fragment Fab, but not Fc of IgG. Because the binding of 125I-pig GPT with the patient's antibody was displaced by human GPT, this antibody may have the characteristic of cross reacting with both pig and human GPT. Although the mechanism of production of the antibody for GPT and the pathological significance of the antibody in chronic hepatic disorders remained obscure, possible inhibition of GPT activity in serum is suggested in the presence of this antibody.

Abnormal serum lactate dehydrogenase isoenzyme in a case of laryngeal carcinoma and thyrotoxicosis

An abnormal lactate dehydrogenase (LDH) isoenzyme was found in the serum of a patient with laryngeal carcinoma and hyperthyroidism. On electrophoresis it migrated as an additional band between LDH-1 and LDH-2. Follow-up studies suggested that this higher molecular weight, rather thermostable LDH isoenzyme, might have originated from the cancer tissue, though a possible relationship with the thyrotoxic state cannot be excluded.

Serum alkaline phosphatase isoenzymes linked to immunoglobulin G

An unusual isoenzyme pattern of serum alkaline phosphatase was found in a patient with skeletal abnormalities due to multiple epiphyseal dysplasia and it was demonstrated that the abnormal pattern was caused by complex formation between serum alkaline phosphatase and immunoglobulin G of the lambda class. Physicochemical studies of the patient's serum alkaline phosphatase showed the properties of an osseous enzyme. Evidence was obtained indicating that the complexing occurred in vitro and that the patient's immunoglobulin G had the ability to bind the hepatic and osseous isoenzymes selectively but not to bile, placental and intestinal isoenzymes. No abnormality was detected in the leucocyte isoenzyme pattern. The relationship between the occurrence of complex formation and the patient's bone disease was not established.

Immunological and electrophoretical approaches to macroamylase analysis

The characteristics of abnormally large-size amylase (macroamylase) of the three patients were studied. Amylase isoenzyme patterns of the three macroamylase samples of agar gel electrophoresis were different from the normal one: a post-beta-globulin or middle-ganna-globulin zone was found in macroamylase, while a fast-gamma, and a pre-gamma-globulin or both zones is found in normal amylase. With gel chromatography at pH 3.4, macroamylase dissociated to normalsized amylase. The electrophoretic patterns of the normal-sized amylase were identical with those of normal amylase. The binding proteins of the macroamylase were identified as immunoglobulin IgG in onecase and immunoglobulin IgA in the other two cases by the immunochemical criteria and immunoenzyme electropherogram. These immunoglobulins bound with serum amylase having normal molecular weight and electophoretic mobility to form macroamylase.

LDH-IgA immunoglobulin complexes in human serum

Human sera containing complexes of lactatedehydrogenase (LDH) and immunoglobulin A (IgA) were studied. Such complexes could be demonstrated in a number of sera with abnormalities in electrophoretic pattern of the LDH isoenzymes. LDH-IgA complexes were observed in a number of sera in which the LDH-2 band was missing, in a serum with all LDH activity in the betta-gamma-globulin region, but also in some sera with only minor abnormalities in the LDH isoenzyme pattern. It is shown that the IgA bound to LDH is of the kappa light chain type. Auto-bodies were not detected in the sera. Therefore, the formation of the LDH-IgA complexes does not seem to be the result of an antigen-antibody reaction.