Biomedical subjects

C Boitard

Publications and source records attributed to C Boitard.

At least 73 records · Page 4Linked to original sources

PubMed1995

HLA-associated heterogeneity of the humoral response to islet antigens in insulin-dependent diabetes.

Insulin-dependent diabetes mellitus (IDDM) is associated with susceptibility HLA class II alleles. Islet cell antibodies (ICA), detected by indirect immunofluorescence on pancreas sections, represent the best marker of the disease. Autoantibodies to glutamic acid decarboxylase (GADA), one major islet antigen, do not totally account for ICA reactivity, suggesting heterogeneity of the anti-islet humoral response. In 97 patients with IDDM we have correlated ICA heterogeneity with clinical markers and DR and DQ alleles. ICA were found in 81% of the patients, and in 33% the serum blocked the binding to islet cells of reference sera with a granular fluorescence pattern. GADA were found in 62% of cases. Patients with high GADA titers and blocking sera were older at onset and less often had a family history of IDDM, suggesting that these antibodies might be a marker of slow progression to IDDM. ICAs were not associated with particular HLA DR or DQ alleles. Conversely, GADA were less frequent than ICA in DR4 subjects but not in the other groups. Moreover, among DR4 non-DR3 patients, GADA were found almost exclusively in DRB1*0401 patients but not in other DR4 subtypes. There was an association of GADA with DQ alleles but it was secondary to linkage disequilibrium between DR and DQ loci. In conclusion, the heterogeneity of the humoral response in IDDM is controlled by HLA class II genes and correlates with clinical heterogeneity.

Adolescent↗

PubMed1995

Family study of linkage disequilibrium between TAP2 transporter and HLA class II genes. Absence of TAP2 contribution to association with insulin-dependent diabetes mellitus.

The polymorphic TAP1 and TAP2 genes encode a transporter protein required for delivery of cytosolic peptides to class I molecules in the endoplasmic reticulum. Associations have been observed between TAP2 alleles and predisposition to autoimmune diseases such as IDDM but their interpretation has been complicated by the existence of LD between TAP2 and HLA class II loci, and conclusions are still contradictory. In order to precisely define LD on class II haplotypes, we performed an extensive familial analysis. A total of 466 individuals from 55 normal families and 49 IDDM multiplex families was studied, providing information on 420 independent haplotypes. The IDDM-predisposing DRB1*03 and DRB1*04 alleles were in strong negative LD with TAP2-B (delta = -0.035 and -0.034, respectively), and positive LD with TAP2-A (delta = + 0.055 and + 0.012). Positive LD was also found between TAP2-B and DRB1*01 and TAP2-C and DRB1*11 alleles. We then addressed the question of whether TAP2 is an independent additional IDDM-protective or predisposing genetic factor. No TAP2 effect was evidenced when considering DRB1*03 and/or 04 patients. A decreased TAP2-B phenotype frequency was observed in DRB1*03- and DRB1*04-negative IDDM patients compared with DRB1*03- and DRB1*04-negative normal controls (38.6% vs 63%, pc < 0.05), but was probably related to a combination of different weak LD between DRB1 and TAP2 alleles. It thus appears that there is no primary association between TAP2 alleles and IDDM. However, TAP polymorphism may allow us to define particular extended HLA haplotypes involved in susceptibility to autoimmune diseases.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1995

Cyclosporin A does not delay insulin dependency in asymptomatic IDDM patients.

OBJECTIVE: To measure the effects of cyclosporin A (CyA) with no insulin therapy on glucose tolerance and beta-cell function in the preclinical phase of insulin-dependent diabetes mellitus (IDDM). RESEARCH DESIGN AND METHODS: beta-cell responses to the intravenous glucose tolerance test (IVGTT), hyperglycemic clamp, intravenous arginine, and intravenous glucagon were evaluated before and after a 6-month course of CyA in seven patients (mean age 19.6 years) with asymptomatic IDDM. RESULTS: Initial insulin secretory responses were severely decreased when the patients were compared with eight healthy control subjects: IVGTT (1 + 3 min): 106 +/- 16 vs. 884 +/- 190 pmol/l (P < 0.001); hyperglycemic clamp: 102 +/- 16 vs. 310 +/- 42 pmol/l (P < 0.001); intravenous arginine: 346 +/- 72 vs. 1104 +/- 168 pmol/l (P < 0.01); and intravenous glucagon: 170 +/- 37 vs. 247 +/- 35 pmol/l (NS). The beta-cell responses remained markedly abnormal after 6 months of CyA, although the response to intravenous glucose and oral glucose tolerance tests improved in three subjects. All the patients became insulin-dependent after 5-36 months. CONCLUSIONS: CyA alone is not a suitable treatment for asymptomatic IDDM. Earlier identification of subjects with substantial beta-cell secretory capacity and newer nontoxic intervention strategies are required for the prevention of IDDM.

Adolescent↗

PubMed1995

Anti-bovine serum albumin antibodies: genetic heterogeneity and clinical relevance in adult-onset IDDM.

OBJECTIVE: To evaluate the prevalence of anti-bovine serum albumin (BSA) antibodies in patients with adult-onset insulin-dependent diabetes mellitus (IDDM) and investigate a possible link between their presence and genetic susceptibility or resistance determined by human leukocyte antigen (HLA) complex. RESEARCH DESIGN AND METHODS: Sera from 60 recent-onset diabetic patients, 5 prediabetic subjects, and 102 healthy control subjects were tested using a radioimmunoprecipitation assay. HLA-DRB and -DQB alleles were determined by means of allele-specific oligonucleotide typing. Islet cell antibodies (ICAs) were assayed by indirect immunofluorescence. RESULTS: Levels of anti-BSA antibodies were significantly higher in IDDM patients (18.1 +/- 3.5%, n = 60) than in healthy control subjects (7.5 +/- 1.2%, n = 102) (P < 0.001), but in only 16.6% of IDDM patients (10 of 60) were the titers above the 95th percentile of control values. Anti-BSA antibody titers were higher in HLA-DR3 and/or -DR4 patients (23.4 +/- 4.9%, n = 41) compared with DR3 and/or DR4 control subjects (3.1 +/- 1.0%, n = 10) (P < 0.001). DR3 IDDM patients showed higher levels of anti-BSA antibodies (26.3 +/- 6.3%, n = 30) than non-DR3 patients (9.9 +/- 2.6%, n = 30) (P < 0.01) and healthy control subjects. Only two out of five prediabetic subjects had significant anti-BSA levels before clinical onset of diabetes. CONCLUSIONS: Our data confirm that antibodies to BSA are present in adult-onset IDDM patients, particularly in HLA-DR3-positive patients. However, the prevalence of anti-BSA antibodies was lower than previously reported in children, and there was a considerable overlap with healthy control subjects. Only two out of the five prediabetic patients demonstrated anti-BSA antibodies. Taken together, these results do not bring strong support to the clinical usefulness of anti-BSA antibodies as a relevant marker in diabetes prediction or diagnosis.

Adolescent↗

PubMed1995

[Eating disorders and metabolic balance in a population++ of young adults with insulin-dependent diabetes].

We have compared the prevalence of Eating Disorders in a population of 69 out-patients with Insulin-Dependent Diabetes Mellitus including a sample of diabetic young women (average year: 23 years) with two control populations (45 medicine out-patients and 54 girl students). The diabetic population didn't present no more eating disorders--measured by self-report questionnaires (EAT, BITE) than the control population. In a sample of 40 diabetic subjects--having participated in a diagnostic structured interview (LENTCA) based on DSM-III-R criteria: nobody has anorexia nervosa, one woman has bulimia nervosa, the lifetime prevalence of bulimia nervosa not otherwise specified was 21% for men and 43% for women. Bulimia Disorders--measured by self report questionnaire (BITE) and noncompliance were linked with poor glycemic control.

Adult↗

PubMed1994

Recirculation, phenotype and functions of lymphocytes in mice treated with monoclonal antibody MEL-14.

The effect of a single injection of an antibody against the peripheral lymph node (PLN) homing receptor or L-selectin (gp90MEL-14) was studied in vivo in C57BL/6 mice. L-selectin is known to be rapidly shed from leukocytes in humans and in mice following activation or cross-linking in vitro. Here we demonstrate that in vivo a single injection of MEL-14 antibody induces a rapid, almost complete and reversible down-regulation of L-selectin expression on both T and B cells. This modulation is dose dependent, specific for L-selectin and lasts for 10 days. On neutrophils, L-selectin expression was moderately decreased, and the injected antibody was detectable on the cell surface for several days. Thus, L-selectin expression after antibody binding in vivo was affected differently on neutrophils and lymphocytes. MEL-14 treatment induces profound alterations of cell traffic. Loss of L-selectin on lymphocytes leads to drastic PLN depletion and increased spleen cellularity. Depleted PLN were highly enriched in MEL-14-/lo, CD44hi and CD11ahi cells, which may represent transiently sessile memory/activated cells. The unresponsiveness in mixed lymphocyte reaction of PLN cells from treated animals and of purified L-selectin- PLN T cells from normal mice supports this view. However, PLN and spleen cells from treated animals responded normally to non-antigen-specific stimuli.

Animals↗

PubMed1994

IDDM: an islet or an immune disease?

Insulin-dependent diabetes develops as a consequence of the selective destruction of insulin-producing cells by an autoimmune reaction. However, the precise series of events which trigger anti-islet autoreactive T cells is still being investigated. Major issues will need to be raised before a comprehensive view of the anti-islet autoimmune reaction can be delineated. These include defining the primary site of activation of autoreactive lymphocytes and exploring hypotheses to explain the chronicity of the diabetes process. These issues all relate with the more general dilemma of the actual role of the islets of Langerhans in breaking self tolerance to beta-cell antigens. By studying non-obese diabetic mice deprived of beta cells following a single injection of a high dose of alloxan at 3 weeks of age, we recently obtained evidence that the activation of autoreactive T cells requires the presence of target islet cells in order to develop.

Animals↗

PubMed1994

Evidence of CD4+ regulatory T cells in the non-obese diabetic male mouse.

The NOD mouse, which shows many features of human IDDM, is extensively used to evaluate the role of T lymphocytes in the pathogenesis of autoimmune diabetes. The development of diabetes in this model appears to be controlled by a finely tuned immunoregulatory balance between autoaggressive T cells and regulatory immune phenomena, the disruption of which may result in destruction of insulin-secreting cells. The absolute requirement of sublethal irradiation to permit transfer of the disease to non-diabetic adult syngeneic mice provides indirect evidence for the presence of regulatory T cells in non-diabetic NOD mice. We have previously reported that the reconstitution of irradiated recipients by CD4+ T cells from nondiabetic female NOD mice blocks the transfer of diabetes by spleen cells from diabetic donors. We now report evidence that anti-CD4 monoclonal antibodies can substitute for irradiation in rendering adult NOD male mice susceptible to diabetes transfer by diabetogenic spleen cells. Efficient diabetes transfer can be achieved in non-irradiated adult NOD recipients provided they are thymectomized and CD4+ T-cell depleted prior to the transfer. The role of thymectomy is to limit T cell regeneration after anti-T cell monoclonal antibody challenge. Our data confirm that regulatory CD4+ T-cells, which efficiently counterbalance diabetogenic cells, are present in adult NOD male animals.

Animals↗

PubMed1994

Multiple DNA variant association analysis: application to the insulin gene region in type I diabetes.

Association and linkage studies have shown that at least one of the genetic factors involved in susceptibility to insulin-dependent diabetes mellitus (IDDM) is contained within a 4.1-kb region of the insulin gene. Sequence analysis has led to the identification of 10 DNA variants in this region that are associated with increased risk for IDDM. These variants are in strong linkage disequilibrium with each other, and previous studies have failed to distinguish between the variant(s) that cause increased susceptibility to IDDM and others that are associated with the disease because of linkage disequilibrium. To address this problem, we have undertaken a large population study of French diabetics and controls and have analyzed genotype patterns for several of the variant sites simultaneously. This has led to the identification of a subset consisting of four variants (-2733AC, -23HphI, -365VNTR, and +1140AC), at least one of which appears to be directly implicated in disease susceptibility. The multiple-DNA-variant association-analysis approach that is applied here to the problem of identifying potential susceptibility variants in IDDM is likely to be important in studies of many other multifactorial diseases.

Diabetes Mellitus, Type 1↗

PubMed1994

The kidney in cyclosporin A-treated diabetic patients: a long-term clinicopathological study.

This was an analysis of the renal investigations performed in 248 cyclosporin A (CyA)-treated patients who had recent-onset type I insulin-dependent diabetes mellitus (IDDM) to assess the clinicopathological relationships, risk factors and predictive indices of CyA nephrotoxicity, and renal function observed with different CyA treatment regimens. There were four different protocols, using initial CyA dosages ranging from 7.5 to 10 mg/kg/day, with dose modification according to serum creatinine concentration, which was measured regularly in some patients for up to 9 years after starting treatment. Kidney biopsies were obtained from 125 patients (74 adults and 51 children) who had received only CyA for an average duration of 13 months before biopsy and had no other sources of renal injury at this stage of IDDM. Of these patients, 58% showed normal or minimal changes on biopsy, 26% showed slight abnormalities, and 16% showed medium-grade (grade III nephropathy) abnormalities. Lesion severity was related to the degree of interstitial fibrosis and tubular atrophy which, in turn, was related to the use of high maximum CyA dosages. Patients' age, and excessive CyA dose and blood trough levels were the main risk factors, and serum creatinine increase was the best predictive factor of CyA-induced nephropathy. However, CyA-induced renal dysfunction was essentially reversible on dosage reduction, and morphological changes were not followed by progressive renal insufficiency when CyA doses were low and adjusted according to serum creatinine levels. We conclude that, at present, it is recommended that low-dose CyA in combination with other non-nephrotoxic immunosuppressive strategies be used in patients with IDDM.

Adult↗

PubMed1993

Genetic analysis of diabetes and insulitis in an interspecific cross of the nonobese diabetic mouse with Mus spretus.

The nonobese diabetic (NOD) mouse is a widely used model for genetic studies of insulin-dependent diabetes mellitus due to the similarities between the murine and human diseases. To aid in the localization and identification of diabetes-related susceptibility genes, we have constructed an interspecific backcross between NOD and Mus spretus (SEG/Pas) mice. Although no diabetic animals were observed in the first backcross generation of (SEG/Pas x NOD) x NOD (BC1), the incidence of insulitis (lymphocyte infiltration of the islets of Langerhans) exceeded 20% after injections of cyclophosphamide, a treatment that provokes an acute form of diabetes in NOD mice. Insulitis, a prediabetic condition, is a useful phenotype in studies of diabetes susceptibility. In the second backcross (BC2) generation, 8% of the animals became diabetic and 76% were found to have insulitis. Genetic mapping studies in the BC2 families confirmed the importance of the major histocompatibility complex region on the severity of insulitis and suggested that additional susceptibility loci were linked to markers on mouse chromosomes 3, 6, and 15. Mus spretus crosses have been an important tool in recent advances in murine genetics, and our results extend their usefulness to the study of a multifactorial disease.

Animals↗

PubMed1993

Protection from insulin-dependent diabetes mellitus is linked to a peptide transporter gene.

HLA class II association with insulin-dependent diabetes mellitus (IDDM) is well established but is still difficult to map to a particular locus. Polymorphism of the genes coding for transporter associated with antigen processing (TAP1 and TAP2), and located in the HLA class II region, was studied in 167 IDDM patients (116 adult-onset and 51 childhood-onset patients) and 98 normal controls using oligotyping after genomic amplification. A dominant protective effect was observed for the TAP2*0201 allele [relative risk (RR) = 0.3, corrected probability (pc) < 0.001]. Conversely, susceptibility to IDDM was associated with apparent homozygosity for the TAP2*0101 allele (RR = 3.4, pc < 0.001). Protection was independent from but additive to the protection conferred by the DRB1*02 DQB1*0602 haplotype (RR = 0.06, pc < 0.05), and antagonistic to the DRB1*03 DQB1*0201 and DRB1*04 DQB1*0302 haplotypes predisposing effect (RR = 1.1, not significant), arguing in favor of an absence of linkage disequilibrium between TAP2 and HLA class II genes. This was assessed by chi 2 analysis. TAP1 allelic distribution was not different among diabetics and controls. A significant association was observed between the presence of TAP2*0101 and that of islet cell antibodies (p < 0.05). These data suggest that the TAP2 gene, which encodes protein required for delivery of antigen peptides to class I molecules in the endoplasmic reticulum, could modulate the autoimmune response leading to beta cell destruction. From a practical point of view, they make the combined screening of HLA class II and TAP2 loci a highly valuable tool in IDDM prediction.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1993

Evidence for antigen driven selection in two monoclonal auto-antibodies derived from nonobese diabetic mice.

The nonobese diabetic (NOD) mouse is a model of human type I diabetes. This diabetes is due to massive infiltration of the pancreatic beta cell of islets by autoreactive T cells (insulitis) followed by the destruction of insulin-producing cells. Circulating autoantibodies are also detected, notably against glutamic acid decarboxylase, peripherin and insulin. Two monoclonal autoantibodies directed against insulin and peripherin were obtained by fusing NOD spleen and myeloma cells. We report here the nucleotide sequence of the genes encoding for the V regions of these two antibodies. Somatic mutations were identified by comparing the light chain nucleotide sequence of one of these autoantibodies with its germline counterpart precursor established from NOD mice after PCR gene amplification. The other one displays N additions on both sides of the D region. These results strongly suggest that both autoantibodies have undergone diversification, either N additions or somatic mutations, and therefore present structural features of antibodies derived from animals immunized against exogenous antigens.

Amino Acid Sequence↗

PubMed1993

Susceptibility to insulin dependent diabetes mellitus maps to a 4.1 kb segment of DNA spanning the insulin gene and associated VNTR.

Recent studies have demonstrated that a locus at 11p15.5 confers susceptibility to insulin dependent diabetes mellitus (IDDM). This locus has been shown to lie within a 19 kb region. We present a detailed sequence comparison of the predominant haplotypes found in this region in a population of French Caucasian IDDM patients and controls. Identification of polymorphisms both associated and unassociated with IDDM has allowed us to define further the region of association to 4.1 kb. Ten polymorphisms within this region are in strong linkage disequilibrium with each other and extend across the insulin gene locus and the variable number tandem repeat (VNTR) situated immediately 5' to the insulin gene. These represent a set of candidate disease polymorphisms one or more of which may account for the susceptibility to IDDM.

Base Sequence↗

PubMed1993

Proliferation and Na+/H+ antiport activity in human fibroblasts from type I diabetic patients with nephropathy.

To investigate whether constitutive alterations of the Na+/H+ antiport or of cell proliferation control mechanisms are implicated in development of nephropathy in insulin-dependent diabetics (IDD), skin fibroblasts from controls, recent-onset IDD with normal or high glomerular filtration rates, and IDD with proteinuria were cultured by explant technique. The Na+/H+ antiport activity was studied using the pH sensitive fluorescent dye BCECF. The cell growth capacity was investigated by determination of cell DNA doubling time and by nuclear [3H]thymidine incorporation in response to serum. The Na+/H+ antiport activity and fibroblast growth capacity did not differ between fibroblasts from controls and IDD patients, suggesting the absence of a genetic alteration of the Na+/H+ antiport in the development of diabetic nephropathy.

Adult↗

PubMed1993

Erythrocyte Na+/Li+ countertransport and glomerular hyperfiltration in insulin-dependent diabetics.

Erythrocyte Na+/Li+ countertransport activity was investigated in 11 controls and 22 recent onset type I (insulin-dependent) diabetic patients with normal and high glomerular filtration rates. No differences in Vmax were observed in hyperfiltering compared to normofiltering patients or controls. The Na+/Li+ activity was correlated with blood glucose levels in insulin-dependent diabetics showing good glycemic control. Total cholesterol and triglyceride concentrations were similar among the three groups. In conclusion, enhanced Na+/Li+ countertransport activity is not associated, in our case, with diabetic condition per se and with early glomerular hyperfiltration and cannot be used as a marker of renal involvement in recent onset insulin-dependent diabetics.

Adult↗

PubMed1993

Role of CD4+CD45RA+ T cells in the development of autoimmune diabetes in the non-obese diabetic (NOD) mouse.

The non-obese diabetic (NOD) mouse spontaneously develops a T cell-mediated autoimmune disease, sharing many features with human insulin-dependent diabetes mellitus (IDDM), leading to insulin-secreting beta cell destruction. The role of CD4+ T cells has been evidenced at two levels. First, CD4+ T cells from diabetic animals are required to transfer diabetes to non-diabetic recipients in conjunction with CD8+ effector T cells. Second, suppressive CD4+ T cells have been characterized in non-diabetic NOD mice. T cells with different functions can thus share the CD4+ phenotype. Since CD4+ T cells can be divided into at least two subgroups on the basis of CD45 isoform expression, we evaluated the distribution of CD4+ T cells expressing the CD45RA isoform on NOD mouse thymocytes and peripheral T cells. The percentage of CD45RA+ cells was dramatically increased among the most mature CD3bright thymocytes and among CD4+ T cells in lymph nodes of the NOD mouse as compared with control strains. This increase was related to the development of insulitis. Interestingly, the CD45RA isoform was expressed on most CD4+ T cells invading the islets. In vivo treatment with an anti-CD45RA mAb prevented the development of insulitis and spontaneous diabetes in female animals but not the transfer of diabetes by T cells collected from diabetic NOD donors. These results indicate that anti-CD45RA mAb is only effective if given before the full commitment of effector T cells to the destruction of islet beta cells. Thus CD4+CD45RA+ T cells play a key role in early activation steps of anti-islet immunity.

Animals↗

PubMed1993

Decreased insulin response to glucose in islet cell antibody-negative siblings of type 1 diabetic children.

Measurement of beta-cell function is an important marker of progression to diabetes in individuals at risk for the disease. Although the peak incidence for the disease occurs before 17 years of age, normal values for insulin secretion were not available in this age group. We performed a simplified intravenous glucose tolerance test in 167 normal children, and in 98 islet cell antibody (ICA)-negative and 12 ICA-positive siblings of diabetic patients. Their age range was 1-16 yr. The first phase of insulin secretion, evaluated as the sum of plasma insulin concentrations at 1 and 3 min, increased with age and was significantly lower in ICA-negative siblings (86 +/- 6 microU/ml, P < 0.002) than in normal controls (115 +/- 6 microU/ml). This difference was not apparent before 8 yr of age. None of the ICA-negative siblings developed diabetes after an average of 4.5 yr. ICA-positive siblings at first study had a first phase insulin response similar to that of ICA negative siblings, but significantly lower than that of the normal controls (74 +/- 13 microU/ml, P < 0.02). The reason for the decreased insulin secretion in ICA-negative siblings is unknown, but could involve a defect in the growth of beta-cell mass or insulin secretion that could be part of the multifactorial pathogenesis of type 1 diabetes.

Adolescent↗