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Biomedical subjects

A Lernmark

Publications and source records attributed to A Lernmark.

At least 235 records · Page 13Linked to original sources
PubMed1987

Molecular cloning of a polymorphic DNA endonuclease fragment associates insulin-dependent diabetes mellitus with HLA-DQ.

A BamHI 3.7-kilobase (kb) fragment detected by an HLA-DQ beta-chain complementary DNA (cDNA) probe and negatively associated with insulin-dependent diabetes mellitus (IDDM) was cloned and sequenced to localize the polymorphism to BamHI sites in intervening sequences of an HLA-DQ beta-chain gene. A probe of the first intervening sequence (IVS 1) showed the BamHI 3.7-kb fragment in 6 of 17 HLA-DR3/4 controls but in 0 of 13 DR-identical IDDM patients. All IDDM patients (13 of 13) had BamHI fragments of 12 and 4 kb, detected in 9 of 17 controls (P less than 0.02). The simple restriction fragment length polymorphism pattern of the IVS 1 probe was exploited by comparing 113 IDDM patients with 177 healthy controls to show increased prevalences in IDDM of the 12-kb (P less than 0.0001) and 4-kb (P less than 0.0001) fragments. In IDDM patients younger than 20 yr at onset, 98% were 12- and/or 4-kb positive, compared with 63% of controls (P less than 0.0001), giving a relative risk of 91.8 for individuals with both fragments. The 12-kb fragment was linked to HLA-DR4, and the 4-kb fragment to HLA-DR3. Both serologic markers were split and a non-DR3/non-DR4 IDDM patient was 4-kb positive. HLA-DQ seems therefore closer, than HLA-DR, to an IDDM susceptibility gene.

Amino Acid Sequence↗
PubMed1987

Spontaneously diabetic BB rats have age-dependent islet beta-cell-specific surface antibodies at clinical onset.

Diabetes-prone BB rats were examined before, during, and after clinical onset of diabetes for the occurrence of circulating islet cell surface antibodies (ICSAs) with a specific binding to islet beta-cells. The presence of ICSA was assessed by incubating serum immunoglobulin fractions with normal Wistar rat islet cells and identifying cell-bound immunoglobulins by indirect immunofluorescence and by a complement-induced cell toxicity reaction. Under the selected experimental conditions, none of the diabetes-resistant rats were ICSA positive over the entire study period (45-120 days of age). In two diabetes-prone BB rat strains, 19 animals developed diabetes with onset between 50 and 120 days. At day 45, none of these animals was positive for ICSA. In rats developing diabetes between 50 and 85 days of age, 7 of 9 animals presented ICSA at clinical onset, determined by either the immunofluorescence or cytotoxicity test. The antibodies bound to insulin-containing beta-cells but not to other islet cell types, and binding was not eliminated by absorption with liver powder. In animals developing diabetes between 85 and 120 days, only 1 of 10 was positive for beta-cell-specific surface antibodies at onset of the disease. After 30 days of insulin treatment, beta-cell-specific antibodies were detectable in 3 of 4 animals of age 50-85 days, whereas only 3 of 12 older rats presented ICSAs that were, in addition, of low titer or affinity. Our data confirm that ICSAs develop in diabetic BB rats and indicate that these antibodies can bind specifically to islet beta-cells compared with other islet cell types.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1987

Detection of islet cell autoantibodies in newly diagnosed diabetic patients using insulin-producing Syrian hamster cells.

An insulin-producing cell line, Clone-16, of hamster origin, was characterized for islet hormone production and for reactivity with islet cell surface (ICSA) and islet cell cytoplasmic (ICA) antibodies in sera from children with newly diagnosed insulin-dependent (Type 1) diabetes mellitus (IDDM). The Clone-16 cells have a doubling time of about 50-60 hr. The cells produced 63 +/- 3 ng (mean +/- SD) immunoreactive insulin and 9.4 +/- 0.3 ng immunoreactive glucagon per day per 10(6) cells, while somatostatin (SRIF) and pancreatic polypeptide (PP) were undetectable. The reactivity with autoantibodies in IDDM sera was assessed by indirect immunofluorescence or 125I-protein A binding assay on intact cells to detect islet cell surface antibodies (ICSA) or on frozen sections of cell pellets to detect islet cell cytoplasmic antibodies (ICCA) by indirect immunofluorescence. Although the proportion of the ICSA-positive Clone-16 cells compared favorably with rat islet cells (r = 0.81; p less than 0.01), we found 5/10 IDDM sera to be positive on rat islet cells but 8/10 on the Clone-16 cells. There was also a good correlation in the 125I-protein A binding assay between mouse islet cells and Clone-16 cells (r = 0.91; p less than 0.01). Frozen sections of Clone-16 cells showed a cytoplasmic immunofluorescence in 8/10 of the IDDM sera and this reaction parallelled the results obtained in the standard indirect immunofluorescence assay with a frozen section of human blood group O pancreas. We conclude that the insulin- and glucagon-producing Clone-16 cells are a useful cell line for detecting islet cell autoantibodies.

Adolescent↗
PubMed1986

Islet cell and 64K autoantibodies are associated with plasma IgG in newly diagnosed insulin-dependent diabetic children.

There is a high prevalence of islet cell antibodies (ICA) and autoantibodies detected against an islet cell protein of Mr 64,000 at the time of clinical diagnosis of insulin-dependent diabetes (IDDM). In view of the biphasic immune response after antigen presentation, the purpose of this study was to determine the presence of ICA and antibodies against the 64,000 islet antigen after separation of IgM from IgG to prevent interference between the two antibody classes. Plasma samples from 10 newly diagnosed IDDM children and 10 healthy controls were precipitated with polyethylene glycol (PEG), and the crude Ig was subjected to Sephacryl S-300 chromatography to separate IgM and IgG. ICA determined by indirect immunofluorescence on frozen sections of human pancreas showed reduced background immunofluorescence intensity in the purified fractions compared with crude plasma. The number of ICA-positive samples among the IDDM patients increased from 7/10 in plasma to 9/10 in the IgG fraction. There was an increase in the ICA titer in 6/9 of the positive samples. All purified IgM samples were ICA negative. Immunoprecipitation experiments by using Nonidet P-40 detergent lysates of [35S]methionine-labeled neonatal rat islets demonstrated that the 64,000 autoantibodies were in the IgG fraction. We found 7/10 IDDM samples to be positive, whereas all controls were negative. The background in the autoradiographic analysis was markedly reduced in the IgG fractions compared with immunoprecipitates with crude or PEG-purified plasma and the IgM fraction. ICA titers did not correlate to the ability of the IgG fraction to precipitate the 64,000 autoantigen. It is concluded that both the ICA and 64,000 autoantibodies are primarily of the IgG class at the time of clinical onset of IDDM, and that purification of IgG from human IDDM plasma facilitates the detection of the rat islet cell 64,000 antigen.

Animals↗
PubMed1986

A simple assay for the detection of antibodies to endocrine islet cell surface antigens.

A simple and sensitive immunoradiometric assay for the detection of islet cell surface antibodies (CIRMA) has been developed. Live, transformed islet cells derived from a liver metastasis of a transplantable islet cell tumor were grown in removable microtiter wells and incubated with antibody. Cell-bound antibodies were quantitated using 125I-labelled second antibodies. The assay was used to detect islet cell antibodies present in sera from non-diabetic and diabetic BB rats and proved to be particularly effective for screening hybridoma supernatants in order to identify monoclonal antibodies recognizing islet cell surface antigens.

Animals↗
PubMed1986

A two-colour immunofluorescence test with a monoclonal human proinsulin antibody improves the assay for islet cell antibodies.

The conventional indirect immunofluorescence assay for islet cell antibodies was compared with a two-colour immunofluorescent assay to detect both islet cell antibodies with fluorescein isothiocyanate-labeled rabbit anti-human IgG and pancreatic B cells with a monoclonal human proinsulin antibody and Texas red-labeled sheep anti-mouse IgG. Determinations of end-point titres showed a correlation between the new two-colour immunofluorescent assay and the conventional indirect immunofluorescent assay in 1) selected sera positive for islet cell antibodies and insulin autoantibodies rs = 0.93 (p less than 0.01) or for islet cell antibodies alone rs = 0.99 (p less than 0.005) and 2) sera from children or young adults with newly diagnosed Type 1 (insulin-dependent) diabetes rs = 0.95 (p less than 0.0001). No interference between the monoclonal human proinsulin antibodies and islet cell antibodies with or without insulin autoantibodies or between the two second fluorescent antibodies was detected. It is concluded that the two-colour immunofluorescence assay is advantageous since it is possible to mix the reagents to avoid a more time-consuming and technically complicated assay, the presence of B cells can be confirmed in each section to permit detection of B cell cytoplasmic antibodies and microscopic evaluation is easier and more accurate, particularly in islet cell antibody negative samples.

Aged↗
PubMed1986

A deletion in a rat major histocompatibility complex class I gene is linked to the absence of beta 2-microglobulin-containing serum molecules.

Class I major histocompatibility antigens are composed of a heavy chain that is noncovalently associated with beta 2-microglobulin (beta 2m). Most class I molecules are membrane bound, but mouse and rat cDNA clones and genes without a functional code for the transmembrane amino acids have been identified. The membrane-associated class I molecules are important in the control of cell-mediated cytotoxicity, while the function of the soluble molecules remains unclear. Previous studies have shown that beta 2m circulates in rat serum in three different molecular weight classes. The first is free beta 2m (Mr, 12,000), the second is about Mr 70,000, and the third is roughly Mr 200,000. In an inbred subline of immunodeficient, diabetes-prone BioBreeding rats (BioBreeding/Hagedorn), previous work detected two restriction fragment polymorphisms in class I major histocompatibility complex genes, one of them a gene deletion on a 7-kilobase BamHI fragment and the other on a 2-kilobase BamHI fragment. In these rats we have found that the third serum beta 2m-binding size class is absent. Analysis of F1 and F2 individuals following cross-breeding between BioBreeding/Hagedorn rats and genetically related (nondiabetic) control BioBreeding w-subline rats demonstrated that the large-size serum peak of beta 2m was associated with the presence of the class I restriction fragments.

Animals↗
PubMed1986

Cloned cell lines from a transplantable islet cell tumor are heterogeneous and express cholecystokinin in addition to islet hormones.

A liver metastasis (MSL) with a remarkable in vitro proliferation potential has been identified in an NEDH rat carrying a transplantable x-ray-induced islet cell tumor. Two insulin-secreting cell lines, MSL-G and MSL-H, with doubling times of 3-5 d were established by repeated limiting dilution cloning. In vivo inoculation of MSL-G cells induced severe hypoglycemia caused by a small but highly heterogeneous tumor as revealed by immunocytochemistry. Whereas most cells stained for the islet hormones, insulin, glucagon, and somatostatin, clustered cells were discovered to contain cholecystokinin (CCK). Additional in vitro-limiting dilution cloning, followed by immunocytochemical characterization, clearly demonstrated the capacity of single cell clones to simultaneously express the same four hormones. Radioimmunoassays with a panel of site-specific antisera of culture supernatants and purified cell extracts showed the MSL-G2 cells to produce, store, and secrete readily detectable amounts of processed and unprocessed CCK. Gastrin was not detected while coexpression of glucagon and CCK were demonstrated. Mutant clones selected for resistance to 6-thioguanine (frequency, 2 X 10(-7] and checked for HAT (hypoxanthine, aminopterin, thymidine) sensitivity retained the capacity for multi-hormone expression. We propose that the MSL tumor contains pluripotent endocrine stem cells. The MSL tumor and the MSL-G2 cells in particular will allow studies of not only CCK biosynthesis and processing but also of mechanisms involved in tumor and islet cell differentiation.

Adenoma, Islet Cell↗
PubMed1986

Monoclonal antibodies against pancreatic islet-cell-surface antigens selected by flow cytofluorometry.

BALB/c mice were immunized with human islets of Langerhans, and spleen cells from two mice, found to develop cell-surface antibodies against insulin-producing rat islet tumour RIN-5F cells, were fused with mouse myeloma cells. Antibody-producing hybrids were cloned on the basis of their production of surface antibodies reactive with paraformaldehyde-fixed RIN-5F cells by indirect immunofluorescence analysis in the fluorescence-activated cell sorter. Among 236 primary clones, eight stable cell lines producing islet-cell-surface antibodies were eventually cloned. Antibody 2G3 (IgM) reacted with viable normal rat islet cells and high insulin-producing rat islet tumour RIN5-A2 cells, while 3G3 (IgM) only reacted with RIN5-A2 cells. Antibody beta B1 (IgG1) reacted with all islet cells tested and detected an Mr21k component in immunoblotting experiments with RIN-5AH cell plasma membrane proteins electrophoretically transferred to nitrocellulose filters. Antibody 7F6 (IgM) reacted with all islet and non-islet cells tested and detected bands of Mr 66k and 27k by immunoblotting. Antibodies gamma B3, gamma B6, gamma C2, and 6B1 (all IgM) showed varying degrees of binding to different islet cells, but reacted only weakly with non-islet human cells. It is concluded that monoclonal antibodies against pancreatic islet cells may define specific endocrine islet-cell-surface determinants.

Animals↗
PubMed1986

Islet cell and other organ-specific autoantibodies in healthy first-degree relatives to insulin-dependent.

The presence of organ-specific autoantibodies including islet cell surface, cytoplasmic and cytotoxic as well as thyroid-gastric antibodies were determined in healthy, non-diabetic, first-degree relatives to 30 insulin-dependent diabetic (IDDM) children. Thirty healthy families without family-history of diabetes mellitus served as controls. The prevalence of organ-specific autoantibodies among the healthy members in the diabetic families was increased compared to the control families (p less than 0.005). Islet cell cytoplasmic antibodies were only detected in diabetes families, since 23% (7/30) of the probands and 7% (2/31) of the siblings were positive and all others negative. Organ-specific autoantibodies were associated with HLA DR3 only in the diabetes families (p less than 0.025) while autoantibody positive members in the control families were associated with HLA B7 (p less than 0.01). This study suggests that childhood IDDM occurs in families with an increased prevalence of organ-specific autoantibodies.

Adolescent↗
PubMed1986

Potentiation of insulin release in response to amino acid methyl esters correlates to activation of islet glutamate dehydrogenase activity.

Column perifusion of mouse pancreatic islets was used to study the ability of amino acids and their methyl esters to influence insulin release and activate islet glutamate dehydrogenase activity. In the absence of L-glutamine, L-serine and the methyl ester of L-phenylalanine, but neither L-phenylalanine nor L-serine methyl ester, stimulate insulin secretion. In the presence of L-glutamine, however, the effect of L-serine was additive, while the methyl esters of L-serine and L-phenylalanine as well as native L-phenylalanine, potentiated the glucose-stimulated release of insulin. Measurements of islet glutamate dehydrogenase activity showed that only the two methyl esters of L-phenylalanine and L-serine activated the enzyme. It is concluded that the mechanism by which methyl esters of amino acids potentiate insulin release is most likely to be mediated by the activation of pancreatic beta-cell glutamate dehydrogenase activity.

Amino Acids↗
PubMed1986

Secretin and its C-terminal hexapeptide potentiates insulin release in mouse islets.

Peptides representing the C-terminal end of secretin were synthetized and their effects tested along with secretin on column-perifused isolated mouse pancreatic islets. Insulin release induced by 10 mmol/l D-glucose was potentiated by secretin tested in a concentration range of 0.01-10 micrograms/ml; the maximal effect was obtained with 1 microgram/ml secretin. This effect was mimicked by 50-500 micrograms/ml NH2-Leu-Leu-Gln-Gly-Leu-Val-NH2, [S-(22-27)], which represents an amidated C-terminal sequence of the secretin molecule. The consecutive smaller secretin C-terminal peptides had either no effects [Val-NH2, S-(24-27)] or only marginally [S-(26-27), S-(23-27)] potentiating effects on insulin release in the presence of 10 mmol/l D-glucose. The effects of secretin and S-(22-27) were not influenced by 2 mmol/l glutamine. The intact hormone and the five synthetic peptides as well as Val-NH2 had no stimulatory effect on islet glutamate dehydrogenase activity. In fact, S-(23-27), S-(24-27), and S-(25-27) inhibited the islet glutamate dehydrogenase activity, the activation by which amino acids and amino acid derivatives are known to elicit a potentiation of insulin release. Our results suggest that the C-terminal part is important to the marked potentiation of glucose-induced insulin release in vitro by secretin.

Animals↗
PubMed1986

Insulin release and pancreatic insulin is reduced in young prediabetic BB rats.

The pancreases of approximately 50 days old diabetes-prone BB/Hagedorn (BB/H) and of the genetically closely related, but non-diabetic BB w-subline (control BB) rats were perfused to determine the capacity of D-glucose to release insulin before the expected development of diabetes. The BB/H rats were from a colony with 82-84% incidence of insulin-dependent diabetes mellitus (IDDM) by 140 days of age. The total amount of insulin released from the BB/H rat pancreas during stimulation with 20 mmol/1 mmol/ D-glucose was reduced by nearly 50% (P less than 0.01). The initial peak of insulin release was similar between the two groups of animals, whereas the amount of insulin released during the second peak accounted for the diminished release (P less than 0.01). The extractable pancreatic insulin was 30% (P less than 0.05) less in the BB/H rats. Total insulin release expressed relative to the pancreatic insulin content, was therefore not different between the two groups. It is concluded that about 20-40 days before the mean age of clinical onset of IDDM in BB/H rats, the capacity to release insulin in response to D-glucose is reduced along with a diminished pancreatic insulin content. This abnormality seems to be preceded only by islet cell surface antibodies but not by insulitis.

Animals↗
PubMed1986

An H-2 alloantiserum preserves beta-cell function in mice made diabetic by low-dose streptozocin.

The pancreatic beta-cell mass and function in C57BL/KsJ mice is markedly reduced the day after the last injection of five daily injections of a subdiabetogenic, 40 mg/kg, dose of streptozocin (STZ). In this study, we prepared an H-2 alloantiserum by injecting C57BL/6J mice (H-2b) with spleen lymphocytes from C57BL/KsJ (H-2d) mice. The alloantiserum given on five consecutive days, 5 h before each injection of STZ, did not prevent the initial beta-cytotoxic effect of STZ detected by perfusion of the pancreas and subsequent morphometric analysis of in situ dithizone-perfused pancreas. However, 12 days after the first injection of STZ, total insulin release in response to D-glucose, total pancreatic insulin, and pancreatic glucagon was greater in the alloantiserum-treated mice compared with controls receiving normal mouse serum. It is concluded that an H-2 alloantiserum may protect the function and amounts of beta-cells remaining after the initial five low-dose STZ injections.

Animals↗
PubMed1985

Locus-specific detection of HLA-DQ and -DR antigens by antibodies against synthetic N-terminal octapeptides of the beta chain.

Antibodies against synthetic peptides representing the class-II antigen HLA-DR and -DQ beta chain N-terminal sequences were prepared in rabbits. The two octapeptides only share two amino acids and enzyme-linked immuno-assays showed the antisera only to bind to its own antigen. Both peptide antisera detected a 29 kDa component in immunoblots of Raji and AL-34 cell plasma membrane proteins separated by SDS gel electrophoresis. The binding of either N-terminal peptide antiserum was selectively inhibited only by the peptide used as antigen. Indirect immunofluorescence analysis by flow cytofluorometry showed specific surface immunofluorescence in 1:100-1:1000 dilutions in lymphoblastoid and blood mononucleated cells. In the latter the binding was primarily confined to monocytes and a subpopulation of lymphocytes. It is concluded that locus-specific immunological reagents to distinguish between beta chains of HLA-DR and -DQ have been prepared by the preparation by the production of antibodies against the N-terminal sequences of each polypeptide.

Amino Acid Sequence↗
PubMed1985

Immunological aspects of type 1 and 2 diabetes mellitus.

IDDM occurs predominantly among individuals being class II antigen HLA-DR 3 and/or 4 positive, while NIDDM is not associated with HLA-D. Although the HLA-DR 3 or 4 specificities are prerequisites for IDDM to develop, their high frequencies (about 60%) in the background population preclude tissue typing as a predictive test, underlined by the observation that less than 50% of monozygotic twins are concordant for IDDM. The presence of a number of immune abnormalities argues that the causes of IDDM may be sought in an altered immune reaction against antigens present in the pancreatic B cells and/or in the environment. The majority of IDDM patients of short duration show both cellular and humoral autoimmunity against the pancreatic B cells. Similar phenomena may be observed in patients initially diagnosed as NIDDM and treated with oral hypoglycemic agents. It has been speculated that these patients have a retarded form of IDDM. It is possible that the combination of specific Class II antigen molecule(s) and an invading antigen (virus, bacterium, chemical etc.) presented to the immune system triggers the formation of effector cells such as B lymphocytes and cytotoxic T lymphocytes which also cross-react with the pancreatic B cells. Multiple exposures to this or related antigens throughout several years may eventually lead a sufficient loss of pancreatic B cells to cause insulin dependence.

Antibody Formation↗