Properties of amylase-linked immunoglobulins

Macroamylasemia attributable to gluten-related amylase autoantibodies: a case report

BACKGROUND

Macroamylasemia (MA) is a benign condition caused by circulating macroamylase complexes of pancreatic or salivary amylase bound to plasma proteins, which cannot be cleared by the renal glomeruli. In most cases, the macromolecular amylase represents a complex of normal amylase and either immunoglobulin A or G and may be a specific antigen-antibody complex. Celiac disease (CD) is a permanent intolerance to ingested gluten that results in immunologically mediated inflammatory damage of the small intestinal mucosa. Several recent population-based serologic surveys have shown CD to be a common disorder, possibly affecting 1 in 200 to 250 individuals in most countries studied, including the United States, where overt CD is rare, indicating a high proportion of subclinical disease. The diagnosis of CD currently rests on the histological demonstration of the characteristic lesion in the small intestine and the subsequent clinical response to the introduction of a gluten-free diet. MA associated with CD has been described in adult patients, and in a few cases, MA decreased or resolved after a strict gluten-free diet. A few single cases of MA have been described in childhood, but no association with CD has been reported so far. We report a girl with CD, autoimmune thyroiditis, and MA, in whom CD-related antibodies to amylase and to exocrine pancreas tissue resolved with a gluten-free diet.

CASE REPORT

An 11-year-old girl was referred for chronic abdominal pain and growth retardation associated with persistent hyperamylasemia and suspected chronic pancreatitis. We confirmed elevated serum amylase, normal serum lipase, and very low 24-hour urine amylase and amylase clearance/creatinine clearance ratio, consistent with MA. Serologic tests for CD were positive, and the diagnosis was confirmed by small bowel biopsy showing subtotal villous atrophy. Thyroid function tests showed a pronounced hypothyroidism, associated with high titers of thyroid microsomal and thyroglobulin antibodies. Screening for other autoantibodies-including antinuclear, islet cell, glutamic acid decarboxylase, protein tyrosine phosphatase islet antigen 512, adrenal gland, and cytoplasmic neutrophil granulocyte antibodies-was negative. A diagnosis of CD, MA, and hypothyroidism attributable to autoimmune thyroiditis was made. A gluten-free diet and oral replacement with L-thyroxine was started with clinical improvement. Serum amylase and amylase clearance/creatinine clearance ratio normalized, consistent with resolution of MA.

STUDY DESIGN AND METHODS

The patient's serum samples were obtained at the time of CD diagnosis and at 3 and 12 months after instituting a gluten-free diet. Serum samples from 10 consecutive untreated celiac children were disease controls, and 39 participants with no gastrointestinal symptoms and no family history of CD served as healthy controls. The origin of MA as determined by complexes of amylase with circulating immunoglobulins was tested by the measurement of amylase on supernatants after precipitation of immune complexes with either protein A Sepharose or polyethylene glycol. The precipitation of >60% of amylase activity was consistent with the presence of MA. Immunoglobulin G (IgG) and immunoglobulin A (IgA) circulating autoantibodies to amylase were measured using recently developed enzyme-linked immunosorbent assay (ELISA), using porcine amylase as antigen. Results were expressed as arbitrary units (AUs). Statistical analysis was performed by Student's t test for unpaired data. IgA and IgG antibodies to exocrine pancreas tissue were detected by indirect immunofluorescence on human pancreas cryosections.

RESULTS

Serum immunoprecipitation with either protein A Sepharose or polyethylene glycol reduced amylase activity from 1698 to 89 U/L (94.8%) and to 75 U/L (95.6%), with only marginal reduction in control serum samples. The ELISA for autoantibodies to amylase detected high values, both IgA (3531 AU) and IgG (1855 AU), in the serum sample from the patient at CD diagnosis. IgA autoantibodies (mean +/- standard deviation) were 3.4 +/- 2.5 AU in healthy controls, and 2.1 +/- 1.2 AU in celiac controls; IgG autoantibodies were 10 +/- 4.8 AU in healthy controls and 8.5 +/- 3.2 AU, respectively. Autoantibodies to exocrine pancreas tissue were documented in patient sera at the time of CD diagnosis, both IgA and IgG, but not in control groups. Preincubation of patient's serum with excess of alpha-amylase specifically inhibited antibody binding to coated amylase in the ELISA, and partially inhibited immunoreactivity to exocrine pancreas. Autoantibodies to alpha-amylase and to exocrine pancreas declined in CD patients after institution of a gluten-free diet.

CONCLUSIONS

Few cases of MA have been described in children, and in all amylase determination was part of the clinical investigation for abdominal pain or trauma. (ABSTRACT TRUNCATED)

Immunochemical study of immunoglobulins bound to lactate dehydrogenase

Immunochemical analysis of lambda type Bence Jones protein (BJP: designated as Suzuki-BJP) and IgG-lambda type M-protein (designated as Miki-IgG), lambda type BJP (designated as Miki-BJP) which showed non-specific binding with lactate dehydrogenase (LD, EC 1.1.1.27) was carried out in two cases. When the purified LD mixed with NADH was eluted through the CNBr-Sepharose 4B coupled to Suzuki-BJP or Miki-IgG, the affinity with these adsorbents was not demonstrated. The amino acid residue of the N-terminal in the Suzuki-BJP and lambda chain of the Miki-IgG was determined to be tyrosine by primary structure analysis, on the other hand, alanine was detected in the gamma chain of the Miki-IgG that did not have LD binding ability. By counter affinity electrophoresis, it was shown that LD bound to a synthetic peptide consisting of 15 amino acid residues of N-terminal which had the same beta-sheet structure as the Suzuki-BJP. It seems probable that LD combines with BJP (or IgG) molecule at the NAD+ binding site producing a three-dimensional structure similar to NAD+.

Hydrolases acting on glycosidic bonds: chromatographic and electrophoretic separations

We describe analyses of unusual human alpha-amylase, performed in our laboratory and review available methods for amylase study. Electrophoretic and chromatographic methods provide an effective means for the analysis of amylase isoenzymes and unusual amylase. The recent identification of a selective inhibitor and a monoclonal antibody to amylase isoenzyme contributes to rapid routine clinical assays of amylase isoenzymes. However unusual amylases such as variants, macroamylasemia and sialyl salivary-type amylasemia cannot be detected by those conventional methods. The unusual amylases can only be detected by electrophoresis and can be easily characterized by combination study with chromatographic methods. Electrophoretic and chromatographic methods are universal means to validate unusual amylases found in patient sera. Further basal studies are needed to define the roles of salivary amylase in exocrine fluids using those separation techniques.

Interactions of galactosyltransferase with serum and secretory immunoglobulins and their component chains

Assay of the activity of beta-1,4-galactosyltransferase (beta-1,4-GT) revealed that in addition to serum, milk, colostrum, amniotic and cerebrospinal fluids and malignant effusions, this enzyme is present also in tears and saliva. Molecular-sieve chromatography of human colostral whey and serum and subsequent assay of beta-1,4-GT activity have shown that beta-1,4-GT was present as a free enzyme (55 kDa) and associated with components of larger molar mass. The elution pattern did not change when the chromatography was carried out in a buffer devoid of, or enriched with, Mn2+, a cofactor of beta-1,4-GT activity. However, the activity associated with the large molar mass components was absent when the chromatography was carried out in the presence of a chelating agent (EDTA). Analyses of the eluted material by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE), and by immunodiffusion indicated that the major colostral component in beta-1,4-GT activity-containing fractions was secretory IgA (S-IgA); in addition, the beta-1,4-GT activity was detected in fractions that contained lactoferrin and alpha-lactalbumin. Interactions of beta-1,4-GT with S-IgA and lactoferrin in colostrum were also demonstrated by the detection of radioactivity in precipitin lines obtained by immunoelectrophoresis and autoradiography of the colostral whey after it had been incubated with UDP-[3H]-galactose. Furthermore, radioactively labeled S-IgA and alpha-chain were detected when colostral whey incubated with UDP-[3H]-galactose was analyzed by SDS-PAGE under non-reducing and reducing conditions, respectively. In serum, the beta-1,4-GT-binding components identified in fractions after molecular-sieve chromatography were IgG, IgA, IgM and transferrin. The binding of beta-1,4-GT to immunoglobulins (Ig) was also demonstrated by assaying the beta-1,4-GT activity associated with Sepharose-4B-immobilized Ig of various isotypes and molecular forms, which were incubated with colostral beta-1,4-GT in the presence of Mn2+. Beta-1,4-GT measured by enzyme activity was bound to these Ig in order: polymeric IgA2 > monomeric IgA1 = polymeric IgA1 = secretory IgA = pentameric IgM > IgG. Immobilized component chains, namely alpha, mu and J chains, bound beta-1,4-GT more effectively than native Ig. Incubation of the IgA1 myeloma protein with crude human colostral galactosyltransferase in the presence of UDP[3H]-galactose and Mn2+ resulted in galactosylation of both N- and O-linked carbohydrate side chains.(ABSTRACT TRUNCATED AT 400 WORDS)

Induction of autoantibodies to human enzymes following viral infection: a biologically relevant hypothesis

Macro enzymes, i.e. complexes of normal (iso-)enzymes with an immunoglobulin, may be due to immunological cross-reactions evoked by specific viral antigenic determinants that are homologous to regions in the target enzymes. A search of the National Biomedical Research Foundation protein databank with the amino-acid sequence of human pancreatic amylase revealed a marked homology with a fragment of the yellow fever virus major envelope protein E: i.e. an overall identity of 19.7 per cent and a high degree (40.9 per cent) of conservative amino-acid substitutions over 119 amino acids. At each identical position, the corresponding residue of Taka amylase A was examined by three-dimensional structure analysis, to determine whether the position is likely to be buried or exposed. The existence of a site (epitope) on amylase recognized by an anti-amylase antibody is discussed.

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.

Monoclonal antibodies to enzymes

The production, identification, and utilisation of monoclonal antibodies to enzymes are reviewed. Such antibodies may be produced in vitro by the mouse-hybridoma technique, may occur naturally in vivo as enzyme-binding immunoglobulins and may be produced in the laboratory from the lymphocytes of patients whose sera contains such immunoglobulins. The diagnostic application of monoclonal antibodies to enzymes is considered, with special reference to their use in the measurement of the MB-isoenzyme of creatine kinase, pancreatic isoamylase, prostatic acid phosphatase, and the isoenzymes of alkaline phosphatase.

Characterization of amylase linked immunoglobulin G to distinguish human salivary and pancreatic isoamylases

An immunoglobulin G of the kappa type linked to salivary amylase was identified in the serum of a patient with colon cancer and persistent hyperamylasemia. The binding site on the immunoglobulin in the complex is located in F(ab')2 portion. The purified IgG recombined only with purified human salivary amylase, and could be used to separate human isoamylases.

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.

Sandwich electroimmunofixation (SEIF) for the assessment of isoenzyme specificities of immunoglobulins isolated from enzyme-immunoglobulin complexes

Sandwich electroimmunofixation (SEIF) was used to determine immunologic specificity for isoenzymes of immunoglobulins isolated from enzyme-immunoglobulin complexes. After electrophoretic separation of isoenzymes, isoenzyme-specific human immunoglobulins obtained from complexes and antihuman immunoglobulin antibodies were applied to the supporting medium and allowed to react. Complexes of isoenzyme-immunoglobulins-anti-immunoglobulin antibodies formed immunoprecipitates and were fixed in the supporting medium. After washout of the unreacted enzymes and proteins with buffer, the immunoprecipitates were stained. A comparison with control enzymograms allowed for a determination as to whether the immunoglobulins reacted with specific isoenzymes. When an immunologic reaction with more than 2 isoenzymes occurred, the specificity was quantitated by densitometry. SEIF, used to examine immunoglobulins isolated from aspartate aminotransferase-, lactate dehydrogenase-, alkaline phosphatase- and amylase-immunoglobulin complexes, was found to be a rapid and reliable technique. This approach showed that immunoglobulins differ in their specificities for various isoenzymes.

A case of rheumatoid arthritis with various enzyme-immunoglobulin complexes

Several complexes of enzymes and immunoglobulins were detected at the same time in the serum of a patient with seropositive rheumatoid arthritis. The enzymes which were found to complex with immunoglobulins were lactate dehydrogenase, alkaline phosphatase (liver, bone, placental, and intestinal isoenzymes), amylase, cytosol leucine aminopeptidase, and microsomal leucine aminopeptidase. Reconstitution studies after papain or pepsin digestion showed that the association site of the enzymes was in the Fab portion of the immunoglobulin component. We found these complexes to be the result of an antibody-antigen reaction. The binding capacity of each enzyme was variable over the entire time course. The patient's immunoglobulins, complexed with lactate dehydrogenase or amylase, could not be reconstituted using alkaline phosphatase, cytosol leucine aminopeptidase, or microsomal leucine aminopeptidase in vitro. Therefore, this suggests that the immunoglobulins which bind to each enzyme are independent of each other.

Characteristics of the complex between alkaline phosphatase and immunoglobulin A in human serum

An abnormal band of alkaline phosphatase (ALP) activity was detected by electrophoresis in the serum of a patient with liver cirrhosis, and was shown to be a complex between ALP and immunoglobulin A (IgA) of the lambda type. Physicochemical studies of ALP in the patient's serum showed properties of liver and bone isozymes. The patient's IgA and its F(ab')2 fragment were prepared by column chromatography, and used in in-vitro reconstitution studies with various ALP isozymes. It was found that only the liver and bone ALP attached to the IgA, while the placental and intestinal ALP did not. The ALP was attached to the F(ab')2 fragment of IgA. It is concluded that this complex is the result of an antibody-antigen reaction. Molecular weights of the two complexes, ALP-IgA and ALP-IgA-F(ab')2, suggest that two molecules of monovalent ALP associated with one molecule of divalent IgA.

Biochemistry of human alpha amylase isoenzymes

The purpose of this article is to review recent literature on the isoenzymes of alpha amylase. Although some studies are cited from the literature of fields other than clinical biochemistry, the aim is to bring together findings that may be of interest to clinical laboratory physicians and scientists. It is hoped that this will be useful in suggesting further studies of amylase. To this end, the review is more selective than exhaustive. The review will discuss the history and chemistry alpha amylases, the measurement of amylase and amylase isoenzymes, posttranslational modifications of human amylases, and the genetics of human pancreatic and salivary amylases. Finally, we will discuss other tissue sources of amylase with emphasis on "genital" amylases and their relationship to the amylase found in serous ovarian tumors.

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.

[Macroamylasemia. Immunoglobulin a-amylase-complexes as rare cause of hyperamylasemia (author's transl)]

A 56 year old diabetic woman with persistent hyperamylasemia, with an extremely low renal clearance of amylase and without signs of pancreatic disease was found to have an abnormally large serum amylase. This macroamylase had a molecular size of 450,000 Daltons in gel filtration and could be dissociated at low pH values. By the use of chromatographic, electrophoretic and immuno-chemical tests, it was possible to identify the macroamylase as a complex formed by immunoglobin A (IgA kappa) along with normal pancreatic and parotic amylase. The immunoglobulins had a high affinity for human pancreatic and salivary amylase as well as for hog pancreatic amylase. It remains unclear if the amylase binding immunoglobulins are autoantibodies. The finding of macroamylasemia should prevent patients from being subjected to superflous investigation and meaningless treatment.

Electrophoretic identification of serum immunoglobulins linked to amylase:macroamylase

The amylase-linked immunoglobulins in 16 cases with macroamylasemia were analyzed by employing immunoelectrophoresis on agar gel plates. The classes of the amylase-binding immunoglobulins were identified as follows: in the heavy chain classes, 10 cases were alpha, two cases gamma, one case both alpha and gamma and three cases could not be identified; in the light chain types, nine cases were kappa, two cases lambda and five cases unidentified.

Macroamylasemia and other chronic nonspecific hyperamylasemias: chemical oddities or clinical entities?

Seventeen patients with chronic hyperamylasemia were studied using standard clinical and laboratory parameters, amylase/creatinine clearance ratios, and polyacrylamide gel electrophoresis of serum amylases. These patients, none of whom had evidence of pancreatic disease or other specific source for the elevated serum amylase, fell into three groups: (1) Normal serum isoamylase profile and normal amylase clearance (6 patients). We postulate that the generalized hyperamylasemia may be due to reduced extrarenal catabolism of amylase, a previously undescribed phenomenon. (2) Macroamylasemia and very low amylase clearance (9 patients). Seven of the nine patients had recurrent epigastric pain. Evidence for an autoimmune basis is discussed. (3) Salivary-type hyperamylasemia and low amylase clearance (2 patients). This entity may really be macroamylasemia in which the macroamylase complex dissociated during analysis. Chronic hyperamylasemia is often not of pancreatic origin. The assumption that the pancreas is at fault, especially if there is abdominal pain, may cause morbidity due to gross overtreatment.

Biochemical and immunological comparison of monkey (Macaca arctoides) and human salivary secretions

1. Salivary secretions of the stumptail monkey (Macaca arctoides) were compared biochemically and immunologically with human salivas. 2. Similarities in biochemical composition and antigenic profiles as seen by immunoelectrophoresis indicate that monkey salivas can provide an excellent model system to study the role of saliva in the oral ecology of man.