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N Maclaren

Publications and source records attributed to N Maclaren.

At least 19 recordsLinked to original sources
PubMed1996

Identification and characterization of glima 38, a glycosylated islet cell membrane antigen, which together with GAD65 and IA2 marks the early phases of autoimmune response in type 1 diabetes.

Immunoprecipitating IgG autoantibodies to glutamic acid decarboxylase, GAD65, and/or a tyrosine phosphatase, IA2, are present in the majority of individuals experiencing pancreatic beta cell destruction and development of type 1 diabetes. Here we identify a third islet cell autoantigen, a novel 38-kD protein, which is specifically immunoprecipitated with sera from a subset of prediabetic individuals and newly diagnosed type 1 diabetic patients. The 38-kD autoantigen, named glima 38, is an amphiphilic membrane glycoprotein, specifically expressed in islet and neuronal cell lines, and thus shares the neuroendocrine expression patterns of GAD65 and IA2. Removal of N-linked carbohydrates results in a protein of 22,000 Mr. Glima 38 autoantibodies were detected in 16/86 (19%) of newly diagnosed patients, including three very young children, who had a rapid onset of disease, and in 6/44 (14%) of prediabetic individuals up to several years before clinical onset. The cumulative incidence of GAD65 and glima 38 antibodies in these two groups was 83 and 80%, respectively, and the cumulative incidence of GAD65, glima 38, and IA2 antibodies in the same groups was 91 and 84%, respectively. GAD65, IA2, and glima 38 represent three distinct targets of immunoprecipitating IgG autoantibodies associated with beta cell destruction and type 1 diabetes.

Adolescent↗
PubMed1996

Autoantibodies to the extracellular domain of the calcium sensing receptor in patients with acquired hypoparathyroidism.

Acquired hypoparathyroidism (AH) has been considered to result from an autoimmune process but the self-antigens have not been identified. We studied 25 patients with AH, of which 17 had type I autoimmune polyglandular syndrome and 8 had AH associated with autoimmune hypothyroidism. Five of 25 (20%) AH sera reacted to a membrane-associated antigen of 120-140 kD in human parathyroid gland extracts using immunoblot analysis. This is the exact size of the calcium sensing receptor (Ca-SR). The AH sera were then tested by immunoblot using a membrane fraction of HEK-293 cells transfected with Ca-SR cDNA. Eight of 25 (32%) AH sera reacted to a 120-140-kD protein, which closely matched that recognized by the anti-Ca-SR IgG raised in rabbits. The Ca-SR cDNA was translated in vitro into two parts in order to identify the antigenic epitopes. By using this technique, 14 of 25 (56%) AH sera were positive to the extracellular domain of the Ca-SR, whereas none of the AH patients sera reacted to the intracellular domain. The reactivity of the positive sera was completely removed after pre-absorption with the Ca-SR containing membranes. Sera from 50 patients with various other autoimmune diseases as well as 22 normal controls were also tested, and none of them was positive. In conclusion, the Ca-SR has been identified as an autoantigen in AH.

Autoantibodies↗
PubMed1995

Insulin immunization of nonobese diabetic mice induces a protective insulitis characterized by diminished intraislet interferon-gamma transcription.

We reported previously that daily injections of isophane insulin prevented both hyperglycemia and insulitis in nonobese diabetic (NOD) mice (Atkinson, M., N. Maclaren; and R. Luchetta. 1990. Diabetes. 39:933-937). The possible mechanisms responsible include reduced immunogenicity of pancreatic beta-cells from "beta-cell rest" and induced active immunoregulation to insulin (Aaen, IK., J. Rygaard, K. Josefsen, H. Petersen, C. H. Brogren, T. Horn, and K. Buschard. 1990. Diabetes. 39:697-701). We report here that intermittent immunizations with insulin or its metabolically inactive B-chain in incomplete Freund's adjuvant also prevent diabetes in NOD mice, whereas immunizations with A-chain insulin or with BSA do not. Adoptive transfer of splenocytes from B-chain insulin-immunized mice prevented diabetes in recipients co-infused with diabetogenic spleen cells, an effect that was abolished by prior in vivo elimination of either CD4+ or CD8+ cells. Insulin immunization did not reduce the extent of intraislet inflammation (insulitis); however, it did abolish expression of IFN-gamma mRNA within the insulitis lesions. Immunizations with insulin thus induce an active suppressive response to determinants on the B-chain that converts the insulitis lesion from one that is destructive to one that is protective.

Animals↗
PubMed1994

The role of tyrosinase in autoimmune vitiligo.

Vitiligo is a common depigmenting skin disease, associated with certain autoimmune endocrinopathies, and autoantibodies to several antigens can be found in melanoma cells. We set out to identify the antigens. We examined 26 patients with vitiligo and associated endocrine disease. Of these, 18 patients (77%) and 8 immediate family members had autoantibodies specific for a 69 kDa protein in HTB-70 human melanoma cells that was not seen in control cells. The autoantibody-positive patient sera reacted with recombinant human tyrosinase expressed in Escherichia coli seen by western blots, as did antibodies raised in rabbits against hamster tyrosinase, but not to recombinant tyrosinase-related protein. Not one of 31 normal controls or 8 patients with alopecia or systemic lupus erythematosus had tyrosinase autoantibodies but a small proportion (12%) of 42 patients with autoimmune endocrine disease without a history of vitiligo had them. The results show that tyrosinase, an enzyme important in melanin formation, is a principal autoantigen of autoimmune vitiligo.

Animals↗
PubMed1994

GAD65 autoantibodies increase the predictability but not the sensitivity of islet cell and insulin autoantibodies for developing insulin dependent diabetes mellitus.

The clinical onset of insulin-dependent diabetes (IDD) can be predicted by determination of autoantibodies to several pancreatic-islet cell antigens. Islet-cell autoantibodies (ICA) and insulin autoantibodies (AA) are most commonly used. We have developed a recombinant human glutamic acid decarboxylase (GAD65) radioimmunoassay and measured autoantibodies to GAD65 (GAD65A) in the sera of 73 documented prediabetic individuals, 76 newly-diagnosed patients, 103 relatives of IDD probands at increased risk for the development of IDD because they were positive for ICA and/or IAA, 72 ICA and IAA negative relatives, and 207 healthy controls. Our data demonstrate that GAD65A are strongly associated with the currently established autoantibody markers of IDD. Their presence in prediabetic subjects with only ICA or IAA enhances their risk for progression to IDD, yet does not much enhance the screening sensitivity already available through conventional ICA and IAA for IDD prediction.

Adolescent↗
PubMed1994

Autoantibody epitope mapping of the 21-hydroxylase antigen in autoimmune Addison's disease.

Patients with idiopathic Addison's disease are characterized by cytoplasmic adrenal autoantibodies, detectable by indirect immunofluorescence of cryocut sections of human adrenal cortex. Recently, autoantibodies that bind a 55-kilodalton protein in the microsomal fraction of adrenal gland extracts identified to be the cytochrome P450 enzyme 21-hydroxylase have been found in Addisonian patient sera. We confirm the finding and report here the autoantigenic epitopes involved in the autoantibody reactivity using recombinant DNA technology. Six cDNA fragments spanning different regions of the 21-hydroxylase gene were expressed as fusion proteins with glutathione S-transferase in Escherichia coli. Immunoblot analyses were used to evaluate the reactivity of the recombinant proteins with patients' sera to determine the autoepitopes involved. We found that a conserved region (amino acids 164-356) reacted with 25 of 30 adrenal autoantibody-positive sera tested. One serum sample reacted only with the amino portion of the 21-hydroxylase (amino acids 1-162). In addition, 4 other enzymes important to steroid hormone biosynthesis, 11 beta-hydroxylase, 17 alpha-hydroxylase, side-chain cleavage enzyme P450, and 3 beta-hydroxysteroid dehydrogenase, were expressed in E. coli, but none of them gave positive autoantibody reactions by Western blot assays, even using sera from 5 patients with type I autoimmune polyglandular syndrome. The availability of recombinant antigens has permitted structural analysis of the autoepitopes involved in the autoimmune response to 21-hydroxylase in Addison's disease. Our findings should lead to the development of a simple and specific tool for immunodiagnosis of the disease.

Addison Disease↗
PubMed1993

The 12th International Immunology and Diabetes Workshop. Orlando, Florida.

The 12th International Immunology of Diabetes Workshop was held during April 1993 in Orlando, Florida, to review research progress since the 11th Immunology of Diabetes Workshop meeting in Nagasaki, Japan, one and a half years before. The NOD mouse may have as many as 10 susceptibility genes, including its novel IA major histocompatibility complex antigen and a defective interferon-gamma receptor, whereas human IDDM is so far known to be encoded by cis and trans complementation products of certain DQ genes on chromosome 6q, and a gene in the insulin-like growth factor II region on chromosome 11p. A unique protein regulator of the X box promotor of the highly susceptible DQB1*0302 allele has also been found. Islet cell antibody negative siblings of IDDM patients appear to have lower than expected abilities to secrete insulin in response to intravenous glucose. Sera from patients before and/or after developing IDDM immunoprecipitate two native proteins of 64,000- and 38,000-M(r) glutamic acid decarboxylase (GAD65) reacting to conformational epitopes. However, a multitude of other autoantibodies often reacting to denatured proteins through linear epitopes have also been identified. The first workshop for GAD antibody assays was successfully completed; however, the 38,000-M(r) antigen has not yet been identified. Other autoantibodies reactive to gangliosides and to sulfatides continue to be reported. Insulitis has come to be recognized as a sometimes protective event. Protective insulitis predominates in older lesions. It can be induced by as disparate means as tuberculin antigen administration, by interleukin-4 treatments, by transfer of T-cell lines generated in autologous mixed lymphocyte responses, and by immunization to insulin B-chain, whereas oral islet cell antigens, such as insulin, can delay diabetes onset in the NOD mouse.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Immunology of diabetes mellitus.

Insulin-dependent diabetes is an autoimmune disease that may be becoming more prevalent. It has a polygenic mode of inheritance with a major gene being present in the HLA DQ locus on chromosome 6. Inferential data suggest that environmental factors may be important to genetic penetrance albeit we still lack proof for involvement of often maligned viruses. Patients with IDD and their families are predisposed to organ-specific autoimmunities which should be routinely screened for. Autoantibodies to insulin, to a beta cell cytoplasmic lipid containing moiety and to a beta cell protein of 64KDa, which is believed to be the GABA forming enzyme GAD, can be used to predict IDD among relatives and probably the general population as well. Immunosuppressive therapy can modify the course of IDD after diagnosis and should be able to delay the clinical onset if given before diagnosis. Rigorous insulin therapy should also be given as needed to control hyperglycemia and avoid glucose toxicity to the islets. Such trials are now underway.

Autoimmune Diseases↗
PubMed1991

Insulin dependent diabetes 1991.

Insulin dependent diabetes (IDD) most often results from the autoimmune destruction of pancreatic beta cells. During this process, autoantibodies to islet cell constituents (islet cell cytoplasm, 64KDa protein [GAD]) and to insulin arise and can be used for disease prediction if found before onset or for classification at onset in cases in which type of diabetes is not clear. Approximately 4-5% of immediate family members have at least one of these antibodies. The younger the age and the higher the antibody titer, the greater the chance of IDD developing. Because studies using immunosuppression in newly-diagnosed IDD have shown transient prolongation of beta cell function, efforts to use such therapies prior to diabetes onset may prevent beta cell destruction and clinical disease. A multicenter trial is underway in Florida to screen relatives for diabetes-related antibodies and then to enter those found positive and at increased risk in a study to prevent diabetes. Details of the study and its rationale are presented.

Autoimmune Diseases↗
PubMed1989

Initial pathogenic events in IDDM.

A workshop sponsored by the National Institute of Child Health and Human Development was held in June 1988 to discuss the initial events in the pathogenesis of insulin-dependent diabetes and to make recommendations for future studies. Better definition of immunological markers to reliably predict the disease will enable the detection and study of the earliest pathogenic events involved. The precise autoimmune mechanisms and the role of the environment, both in the initiation of the disease process and precipitation of clinically overt disease, need to be accurately determined to define strategies that might eventually lead to its prevention.

Animals↗
PubMed1989

Genetic conditions among Canadian Mennonites: evidence for a founder effect among the old colony (Chortitza) Mennonites.

Distinctive disease patterns exist among Canadian Old Colony (Chortitza) Mennonites. This religious and genetic isolate is of 16th century Dutch/German ancestry. The group originated in the Netherlands, then settled in the Vistula delta area of western Prussia for 200 years. A small number of founding families later migrated to Chortitza, the "Old Colony", in the Ukraine in the late 18th/early 19th century, where they remained a distinct genetic isolate. This group has come to Canada over the past 100 years. The more conservative Canadian Mennonites of Chortitza descent practice strict endogamy, have a large family size and live predominantly in rural public health subdistricts in the four western provinces, and in southern Ontario. The world's largest reported familial aggregations of insulin-dependent diabetes mellitus, of autoimmune diseases and of Tourette syndrome were initially ascertained in a small northern Alberta public health subdistrict. Clusterings of malformations, inborn errors of metabolism, and other conditions were also found in the subdistrict, and in group descendents living in other provinces. A founder effect, or genetic drift, accounts for the familial aggregations of autosomal recessive and dominant conditions, some diseases of multifactorial determination, and other inherited conditions in Canadian kinships descending from this ancestral group. The medical literature on genetic conditions among Canadian Mennonites is reviewed and re-evaluated in the light of this information. There is biochemical, serologic, and molecular biologic evidence in favour of genetic homogeneity amongst patients with certain inherited conditions in this special population group. This genetic isolate offers potential for the study of the genetic epidemiology and molecular biology of inherited diseases. A computerized genealogic data base on about 1400 group members, as well as a cryopreserved lymphocyte/DNA bank on over 100 individuals with genetic conditions has been established in this special population group.

Alberta↗
PubMed1988

Immunosuppression with azathioprine and prednisone in recent-onset insulin-dependent diabetes mellitus.

We randomly assigned 46 patients (mean age, 11.7 years; range, 4.5 to 32.8) with newly diagnosed insulin-dependent diabetes mellitus within two weeks of beginning insulin to receive either corticosteroids for 10 weeks plus daily azathioprine for one year or no immunosuppressive therapy. Half the 20 immunosuppressed patients completing the one-year trial had satisfactory metabolic outcomes (hemoglobin A1c less than 6.8 percent; stimulated peak C peptide greater than 0.5 nmol per liter; insulin dose less than 0.4 U per kilogram of body weight per day) as compared with only 15 percent of the controls. Three of 20 immunosuppressed patients, but no controls, were insulin independent at one year. Two of these continue to receive azathioprine without insulin after more than 27 months of follow-up. The response to immunosuppression correlated with older age, better initial metabolic status, and lymphopenia (less than 1800 lymphocytes per cubic millimeter) resulting from immunosuppression. The side effects of azathioprine included vomiting in one patient and mild hair loss in several others. Prednisone use resulted in a transient cushingoid appearance, weight gain, and hyperglycemia. The growth rate remained normal in all patients. We conclude that early immunosuppression with short-term use of corticosteroids plus daily azathioprine can improve metabolic control in some patients with insulin-dependent diabetes mellitus, but results from this unblinded study are preliminary and require further confirmation and long-term follow-up.

Adolescent↗
PubMed1988

Inherited susceptibility to insulin-dependent diabetes is associated with HLA-DR1, while DR5 is protective.

Of the HLA allelic associations with insulin-dependent diabetes (IDD) reported to date. DR3 and DR4 have been the most positive and DR2 the most negative. In 952 Caucasian proband patients reported here, only 57 or 6% had no DR3 or DR4 alleles. When these 57 patients were compared to 249 Caucasian controls similarly lacking DR3 and DR4 antigens, there were excesses of DR1 (P = 0.13) and DRW8 (P = 0.01) and deficiencies of DR2 (P = 0.03) and DR5 (P = 0.03) in the patient group. The most common phenotype in this group of patients was DR1/DR7 (12.3%). Only four DR-homozygous patients involving alleles other than DR3 and DR4 were found by genotyping, and all were DR1 homozygotes. Among 506 patients wuth DR3/DRX or DR4/DRX phenotypes, DR1 was more frequent (P = 0.001; Bonferronni P = 0.006), and DR2 (P = 0.001) and DR5 (P = 0.001) less frequent than 243 HLA-matched controls. Of 187 patients with a single DR3 and no DR4, DR1 was more frequent (P = 0.02), with DR2 (P = 0.001) and DR5 (P = 0.02) less frequent than 94 HLA DR-compatible controls. Among 319 patients with a single DR4 but no DR3, DR1 was again more frequent (P = 0.01) and DR2 (P = 0.001) and DR5 (P = 0.001) less frequent than 149 HLA-matched controls. We conclude that DR1 is an additional risk DR allele for IDD to that of DR3 and DR4, and DR5 an additional protective DR allele to that of DR2.

Adolescent↗
PubMed1987

Polymorphisms of DQ beta genes in HLA-DR4 haplotypes from healthy and diabetic individuals.

The restriction fragment length polymorphism (RFLP) of DQ beta was assessed in a panel of control and insulin-dependent diabetes (IDD) patients who were serologically typed as HLA-DR4 homozygotes or HLA-DR3, DR4 heterozygotes. Digestions of genomic DNA with Bam HI, Bgl II, Pst I, Xba I, and Hind III revealed a total of 15 RFLPs in the panel of 71 HLA-DR4 chromosomes. These RFLPs were organized into six allelic groups on the basis of segregation analysis in families. Complete RFLP haplotypes for the 5 restriction enzymes could be constructed for 42 of the HLA-DR4 chromosomes. This analysis revealed 18 RFLP haplotypes of DQ beta associated with the DR4 chromosomes tested. Two of these haplotypes, designated DQ3.DR4. a and DQ3.DR4.b, accounted for over 50% of the DR4 chromosomes analyzed. These two haplotypes were antithetical for the RFLPs detected by all five enzymes, indicating that they represent very distinct forms of DQ beta. The remaining 16 haplotypes were infrequent or unique and were closely related to either a DQ3.DR4.a or DQ3.DR4.b. Two of the RFLPs detected, a 5.8 kb Bgl II fragment and a 10.5 kb Bam HI fragment, had increased frequencies in disease-associated chromosomes. However, none of the RFLPs we detected exhibited a statistically significant increase in IDD or control populations. In contrast, the DQ3.DR4.b DQ beta haplotype was significantly decreased in IDD-associated DR4 chromosomes (P = 0.04). These results suggest that the DQ3.DR4.b DQ beta allele may be protective for the development of IDD.

Alleles↗