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Biomedical subjects

A Lernmark

Publications and source records attributed to A Lernmark.

At least 253 records · Page 14Linked to original sources
PubMed1985

Isolation of a rat immune response gene identical to an alleged mouse a class II beta-chain pseudogene.

A human HLA-DQ beta-chain cDNA was used as a probe to identify and isolate a rat major histocompatibility antigen beta-chain gene from a genomic library constructed in the vector lambda Charon 28 using Wistar rat DNA (RT1u). The isolated exon of the rat gene (RT1.B beta 2) encoding a beta-chain second domain was found to share 93% nucleotide homology with a mouse A beta 2 exon. Although the genomic organization of this gene is consistent with the hypothesis that it represents a pseudogene, the remarkable preservation of a specific sequence favors the view that this class II antigen beta-chain gene has retained its coding function.

Amino Acid Sequence↗
PubMed1985

Increased reduction in fasting C-peptide is associated with islet cell antibodies in type 1 (insulin-dependent) diabetic patients.

A cohort of 82 patients with Type 1 (insulin-dependent) diabetes was followed prospectively for 24 months, and 54 of them for 30 months, to study the relationship between fasting levels of immunoreactive C-peptide and titres of islet cell antibodies. After diagnosis, fasting C-peptide rose temporarily for 1-6 months of insulin therapy and declined continuously thereafter. While islet cell antibodies were present among 55% of the newly diagnosed patients, only 31% remained positive at 30 months. Their antibody titres decreased from 1:81 at diagnosis to 1:3. Only 3 patients (4%) who were islet cell antibody negative at diagnosis became positive later. The median C-peptide values among the persistently islet cell antibody positive patients decreased from 0.11 pmol/ml at 18 months, to 0.09 pmol/ml at 24 months, to 0.06 pmol/ml at 30 months compared to 0.18 (p = 0.04), 0.15 (p = 0.05) and 0.16 (p less than 0.003) pmol/ml, respectively, for the islet cell antibody negative patients. The median slope for the latter was -0.09 compared to -0.19 for the islet cell antibody positive patients (p = 0.01). These differences were reflected in increasing dosages of insulin, since patients remaining antibody-positive for 30 months were given 1.3-1.4 times more insulin (p = 0.01-0.004) than the antibody negative patients. This study demonstrates that islet cell antibodies may be a useful marker for predicting an increased rate by which endogenous B cell function is lost in Type 1 diabetes.

Adolescent↗
PubMed1985

Cortisone fails to affect levels of islet cell surface antibodies and incidence of diabetes in the BB rat.

Cortisone acetate (250 micrograms/kg X day) was given by im injections to 40 21-day-old diabetes-prone BB rats. The animals were followed longitudinally to determine islet cell surface antibodies (ICSA), as an expression of an abnormal immune reaction against the pancreatic islet cells and plasma glucose to estimate the degree of metabolic control. ICSA were detected 10-150 days before the diagnosis of diabetes. In the cortisone-treated group the diabetic rats showed significantly higher ICSA values compared to the nondiabetic ones, both in frequency of positive tests (P less than 0.05) and in mean binding values (P less than 0.02). In the control group, no difference in ICSA levels were seen between diabetic and nondiabetic rats. The cortisone regimen also failed to influence the degree of insulitis, commonly associated with diabetes in these rats. These experiments in well defined animals which spontaneously develop diabetes do not support the use of low dose cortisone treatment in attempts to improve or prevent insulin-dependent diabetes in human subjects.

Animals↗
PubMed1985

Identification of an HLA-DQ beta-chain related genomic sequence associated with insulin-dependent diabetes.

Restriction fragment length polymorphism detected by a cDNA probe for an HLA-DQ beta-chain gene has revealed a HLA-DR4 linked BamH1 3.7 kb fragment which is rarely found among insulin-dependent diabetic patients. The present analysis demonstrates that the BamH1 3.7 kb fragment present on a HLA-DR4 positive chromosome in a healthy individual contains coding sequences for an HLA-DQ beta-chain gene and that the absence of this fragment among HLA-DR4 positive insulin-dependent patients is due to the loss of a BamH1 restriction within an intervening sequence.

Base Sequence↗
PubMed1985

Diffusion of C-peptide but not proinsulin from islets in frozen sections of human pancreas identified by monoclonal antibodies.

Human proinsulin (HPI) and C-peptide (HCP) were visualized by specific monoclonal antibodies (Mab's) in the conventional indirect immunofluorescent assay for ICA (islet cell cytoplasmic antibodies) on frozen sections of human pancreas. Two different Mab's GS-9A8 (anti-HPI, mouse IgG1) and GN-ID4 (anti-HPI/HCP, rat IgG2a) showed both intense islet cell cytoplasmic staining. In contrast to the anti-HPI staining which was confined to cell bodies only the GN-ID4 Mab produced an additional extensive staining of treadlike structures radiating from the islets. Both types of staining were blocked by excess HPI. Staining of fixed islet cell tissue were identical for the two different antibodies. Double-staining experiments clearly demonstrated that HCP but not HPI may diffuse from islets in sections of frozen human pancreas. It is concluded that antibodies cross-reacting with HCP do not define (pro) insulin containing cells.

Antibodies, Monoclonal↗
PubMed1985

Islet cell antibodies in insulin-dependent (type 1) diabetic children treated with plasmapheresis.

Plasma levels of islet cell cytoplasmic and cytotoxic antibodies were determined in 10 children with insulin-dependent diabetes mellitus (IDDM) treated with plasmapheresis shortly after diagnosis, and in 9 children with IDDM treated by conventional means alone. Islet cell cytoplasmic antibody (ICA) titers were determined by indirect immunofluorescence using unfixed sections of human pancreas, and islet cell cytotoxic antibody levels were determined in a complement-dependent antibody-mediated cytotoxicity (C'AMC) assay using a human fetal cloned insulin-producing cell line (JHPI-1) as target. Before plasmapheresis, ICA was present in 7 out of 10 children and C'AMC was positive in 4. Four successive treatments with plasmapheresis did not consistently decrease plasma levels of ICA or C'AMC. ICA was present in 15 out of the total 19 children at diagnosis, and titers of ICA decreased in 12 out of 15 subjects by at least 1 degree of dilution (1:3) at 18-30 months follow-up, whether or not they had been treated with plasmapheresis; C'AMC was positive in 6 out of the 18 children at diagnosis and decreased in 2 out of 6. Plasma levels of C-peptide did not differ at diagnosis but remained higher in the plasmapheresis treated diabetic children at 3 and 18-30 months follow-up. Neither ICA titers nor C'AMC levels correlated with plasma C-peptide responses at 18-30 months. It is concluded that plasmapheresis decreases ICA and C'AMC but is followed rapidly by a rebound effect, and does not affect the rates at which these islet cell antibodies decrease with increasing duration of IDDM.

Adolescent↗
PubMed1985

Immune complexes in insulin-dependent diabetes.

Circulating immune complexes (IC) were studied in 40 newly-diagnosed insulin-dependent diabetics (IDDM), 40 long duration IDDM, and 16 healthy controls. IC were detected by the solid-phase Clq test (SP-Clq). IDDM patients at diagnosis (25%) showed a higher incidence of IC compared to the long duration IDDM patients (15%) and the control group (7%). There was no difference in the prevalence of circulating IC in long duration IDDM with clinical nephropathy and those without clinical nephropathy. IC detected by Sp-Clq, seem to be associated with the clinical onset of IDDM but not with the development of nephropathy.

Adult↗
PubMed1984

Autoantibodies to a 64-kilodalton islet cell protein precede the onset of spontaneous diabetes in the BB rat.

Spontaneous insulin-dependent diabetes mellitus (IDDM) in the BB rat is associated with the presence of antibodies to a 64-kilodalton rat islet cell protein. These protein antibodies appeared in young animals and remained for as long as 8 weeks before the clinical onset of IDDM. Antibodies to a 64-kilodalton human islet cell protein were found to be associated with human IDDM. Detection of the antibodies may therefore be used to predict an early immune reaction against pancreatic B cells.

Animals↗
PubMed1984

A beta-cell glycoprotein of Mr 40 000 is the major rat islet cell immunogen following xenogenic immunisation.

An antiserum (R2) was raised in a rabbit against dispersed Sprague Dawley rat islet cells. The R2 antiserum contains islet cell surface antibodies, which mediate complement-dependent cytotoxicity against islet cells resulting in a block of glucose induced insulin release. Immunoprecipitation and gel electrophoretic analysis showed that R2 specifically recognizes an Mr 40 000 glycoprotein present in both rat islet and rat insulinoma cells. This glycoprotein is amphiphilic in character and probably represents a pancreatic beta cell specific plasma membrane component. The results support previous observations in mouse beta cells that a plasma membrane glycoprotein of Mr 40K constitutes a major islet cell immunogen.

Animals↗
PubMed1984

Islet cell surface and lymphocyte antibodies often precede the spontaneous diabetes in the BB rat.

The diabetic syndrome of the BB rat shows many homologies with that of human insulin-dependent diabetes and evidence that the onset of the disease is associated with the presence of autoantibodies, including islet cell surface antibodies. In this study, sera were sampled serially from weaning to 157 days of age from 26 BB rats in two low-incidence litters, and 22 rats of three high-incidence litters. Clinical and metabolic variables were monitored concurrently with blood lymphocyte counts. Islet morphology was correlated at sacrifice. In the high-incidence litters, eight rats developed insulin-dependent diabetes, five impaired glucose tolerance, and the remaining nine all showed insulitis. In the low-incidence litters, only one animal showed impaired glucose tolerance and another insulitis. In the high-incidence litters 16 rats (73%) had islet cell surface antibodies compared with 4 out of 26 (15%) low-incidence controls (p less than 0.002). Antibodies reactive with Wistar rat spleen lymphocytes were present in all high-incidence rats compared with 19% (5 out of 26) among the control litters (p less than 0.002). Time courses of islet cell surface and lymphocyte antibody appearance and their peak values varied, but already at weaning the levels of both antibodies were increased among the high-incidence litter rats (p less than 0.001). Islet cell surface and/or lymphocyte antibodies were therefore present in the majority of animals at an age where neither morphological nor metabolic evidence of the diabetic syndrome were yet detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

In vitro lymphocyte recognition of islet cells following in vivo priming with allogeneic murine pancreatic islets.

Lymphocytes from patients with insulin-dependent diabetes have been shown to be sensitized to pancreatic tissue antigens. Mice immunized with homologous pancreatic islets have been found to develop glucose intolerance and insulitis. Since lymphocytes may be involved in diabetogenesis, we wished to determine if lymph node cells from islet-immunized mice can recognize and respond to islet cells in vitro. A.TL female mice were immunized with an emulsion of BALB/c islet homogenate and complete Freund's adjuvant (CFA); sham-treated A.TL mice were injected with adjuvant and water. Mice were sacrificed 7-8 days later and the draining lymph nodes were removed. The lymph node cells were co-cultured with freshly prepared irradiated BALB/c islet cell, which served as stimulator cells. The co-cultures were incubated for 24-26 h at 37 degrees C, followed by a 16 h [3H]thymidine (TdR) pulse. A significant proliferation of lymph node cells from islet-primed mice was induced during the in vitro stimulation with irradiated islet cells when compared with lymph node cells from sham-treated mice (P less than 0.001). The response may be islet-cell-specific, since irradiated lymph node cells from BALB/c mice failed to elicit a proliferative response under the same culture conditions (P greater than 0.80).

Animals↗
PubMed1984

Spontaneous in vitro immunoglobulin secretion at the diagnosis of insulin-dependent diabetes.

Blood mononuclear cells obtained from 17 newly diagnosed insulin-dependent diabetic (IDDM) patients treated with insulin for 5-7 days were assessed for the number of spontaneous and pokeweed mitogen (PWM)-stimulated immunoglobulin-secreting cells in a reverse haemolytic plaque assay. The spontaneous in vitro immunoglobulin secretion was evanescent and decreased in individual patients within 1-4 months of insulin treatment. Compared to matched controls, 53% (9/17) of the IDDM patients had an elevated spontaneous secretion of immunoglobulin, 41% (7/17) for IgG, 35% (6/17) for IgM, and 35% (6/17) for IgA. The quantities of PWM-stimulated IgG, IgM, or IgA secreting cells in IDDM were comparable to the controls. The IDDM patients with spontaneous immunoglobulin secreting cells had higher fasting C-peptide levels compared to the patients with immunoglobulin-producing cells within the normal range (P less than 0.05). The average titre of islet cell cytoplasmic antibodies was 1:26 in (9 out of 9 were positive) patients with, compared to 1:1 in patients (4 out of 8 were positive) without spontaneous secretion (P = 0.025). These results suggest that the clinical onset of IDDM is associated with a polyclonal B lymphocyte activation and that higher levels of fasting C-peptide islet cell antibodies are associated with this immunoregulatory abnormality.

Adolescent↗
PubMed1984

Susceptibility to insulin-dependent diabetes defined by restriction enzyme polymorphism of HLA-D region genomic DNA.

DNA fragments complementary to cloned sequences encoding HLA-D region class II antigen alpha- and beta-chains were determined by genomic blotting with DNA from HLA-typed members of 22 complete families, 12 of which had a proband with insulin-dependent diabetes mellitus (IDDM). Analysis of genotypes showed that the DNA sequences were linked to HLA-DR and permitted confirmation of recombinations in two families. Digestion with the restriction enzymes BamHI, EcoRI, and PstI and hybridization with an HLA-D region beta-chain cDNA probe confirmed a BamHI 3.7 kilobase (kb) fragment present at low frequency among diabetic individuals and a BamHI 3.2 kb fragment that was also decreased among the diabetic subjects compared with siblings (P less than 0.05) as well as nonrelated control siblings (P less than 0.02) and their parents (P less than 0.01). BamHI 12.0 kb (P less than 0.05) and 5.8 kb (P less than 0.02, P less than 0.02), EcoRI 20 kb (P less than 0.05, P less than 0.02), and PstI 6.0 kb (P less than 0.05) fragments were more frequent in diabetic individuals compared with nonrelated control siblings or their parents, respectively. Analysis of individual haplotypes revealed that HLA-DR4-containing chromosomes were heterogeneous among controls but that the diabetic individuals showed a similar pattern of restriction fragment length polymorphism. Genomic blotting of blood lymphocyte DNA with a cDNA clone encoding the chain of HLA-D region class II antigens permits detection of fragments that are strongly associated with IDDM.

Adolescent↗
PubMed1984

A prospective analysis of islet-cell cytotoxic antibodies in insulin-dependent diabetic children. Transient effects of plasmapheresis.

We determined the effects of plasmapheresis on cytotoxic antibodies to islet cells in 10 children (aged 11-16 yr) with newly diagnosed insulin-dependent diabetes mellitus (IDDM), as well as the plasma levels of antibodies over the next 30 mo and their relation to serum C-peptide concentrations. Complement-dependent, antibody-mediated cytotoxicity (C'AMC) in plasma was measured in a 51Cr release assay using monolayers of the rat islet cell line RINm5F. Cytotoxic antibodies decreased in most IDDM subjects treated by plasmapheresis four times within 2 wk of diagnosis; however, the decreases were small and lasted less than 2-3 days. Thus, both before and after plasmapheresis, 7 of the 10 IDDM children were C'AMC-positive (51Cr release greater than 2 SD above mean for 13 healthy children). After 18-30 mo, only 2 of the original 7 IDDM children with C'AMC-positive plasmas were still positive, and 1 of the original 3 IDDM children without significant cytotoxicity had become positive. Meal-stimulated serum C-peptide responses, measured from diagnosis to 18-30 mo later, did not correlate with C'AMC values. We conclude that (1) plasmapheresis has only transient effects on islet-cytotoxic antibody levels in children with IDDM; (2) these antibodies decrease in most, but not all, subjects over the first 18 mo after diagnosis; and (3) the level of cytotoxic antibodies in IDDM plasma at diagnosis has no predictive effect on residual B-cell function.

Adolescent↗