Biomedical subjects
J F Bach
Publications and source records attributed to J F Bach.
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.
Insulin-dependent diabetes mellitus as a beta-cell targeted disease of immunoregulation.
Explore the source record for details and available documents.
Tolerance induction in transplantation and autoimmune diseases.
Explore the source record for details and available documents.
Molecular analysis of TCR junctional variability in individual infiltrated islets of non-obese diabetic mice: evidence for the constitution of largely autonomous T cell foci within the same pancreas.
Insulitis develops in non-obese diabetic (NOD) mice as a multicentric and asynchronous process. In an effort to understand how this T cell mediated process expands within each islet and propagates between the islets of the same pancreas, we have analyzed the junctional diversity of TCR V beta 6 and V beta 8.2 transcripts cloned from infiltrated islets. The material examined was obtained from individual islets of 8 and 12 week old NOD mice or from pooled islets of 4 week old individual mice. Compared with spleen transcripts, where every V beta 6 or V beta 8.2 clone displays a different junction, islet transcripts are considerably less diverse. Each islet harbors from one to a maximum of six independent CDR3 sequences out of 10 or more analyzed colonies. On the other hand, there is an overall diversity of sequences when comparing the islets of the same pancreas or individual mice at 4 weeks. Altogether, these results support the idea that TCR repertoires are already divergent at the very early onset of insulitis and that each islet-centered infiltrate develops rather autonomously from the oligoclonal expansion of a limited set of precursors. Recirculation between islets is limited and does not seem to be the main mode of propagation of insulitis. Finally, a close analysis of J beta usage and N additions in beta chain transcripts from infiltrating cells reveals definite biases suggestive of an ongoing selective process imposed upon intra-pancreatic T lymphocytes.
T cell activation through Thy-1 is associated with the expression of a surface protein (p100) on a subset of CD4 cells.
Thy-1 molecules, which lack a transmembrane domain, can nonetheless induce T cell activation; it has thus been suggested that a separate transmembrane molecule associated with Thy-1 is required for signal transduction. We have previously characterized a transmembrane protein with an Mr of 100,000 (p100), which is non-covalently bound to two glycosyl-phosphatidylinositol (GPI)-linked molecules, Thy-1 and ThB. p100 is selectively expressed on the T cell surface and divides peripheral CD4 cells into two subpopulations. This differential expression on CD4 cells allowed us to investigate the role of p100 in signal transduction through Thy-1 molecules. Here we report that only p100+ CD4 cells proliferate and release cytokines in response to cross-linkage of Thy-1, although both p100+ and p100- CD4 cells strongly express Thy-1 on their surfaces. Control stimulation by anti-CD3 antibodies or concanavalin A induces identical thymidine uptake by the two CD4 cell populations. Interestingly, these two populations of CD4 cells had different cytokine release profiles after activation through CD3: only p100+ CD4 cells released high amounts of IL-2 and IFN-gamma, whereas both populations released IL-4. p100 expression correlates with the induction of homotypic aggregation of T cells after Thy-1 triggering. p100 is associated with kinase activity (fyn and lck), and phosphorylated proteins of 90, 59, 57 and 33 kDa co-precipitate with Thy-1 only in p100+ CD4 cells. Altogether, these data suggest that p100 is involved in signal transduction through Thy-1. p100 expression by activated CD4 cells in vivo may be relevant to the proposed function of Thy-1 as an accessory signaling molecule in cell activation.
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.
Immunosuppression in insulin-dependent diabetes mellitus: from cellular selectivity towards autoantigen specificity.
Explore the source record for details and available documents.
Fc alpha receptors mediate release of tumour necrosis factor-alpha and interleukin-6 by human monocytes following receptor aggregation.
The functional capacity of the human monocyte receptor for the Fc portion of IgA (Fc alpha R) in mediating signal transduction was evaluated by cytokine release. F(ab')2 fragments of anti-Fc alpha R monoclonal antibodies (mAb) were used as specific probes to induce release of tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6). Multivalent cross-linking by a secondary anti-mouse antibody [F(ab')2 fragments] induced a significant release of TNF-alpha and IL-6 by human blood mononuclear cells, indicating requirements for Fc alpha R aggregation on the cell surface to transmit signals. Both cytokines were released exclusively by adherent cells, identifying monocytes as the responding cells within the mononuclear cell population. This cytokine release could not be due to contaminating endotoxins, because it was not abolished by polymyxin B, a lipopolysaccharide (LPS) inhibitor. Moreover, purified recombinant soluble Fc alpha R inhibited the anti-Fc alpha R mAb-mediated cytokine release from blood monocytes, demonstrating that TNF-alpha and IL-6 were released in a receptor-specific manner. Our data suggest that Fc alpha R, through its capacity to mediate secretion of IL-6, may play an important role in B-cell proliferation and immunoglobulin production. On the other hand, release of TNF-alpha following stimulation of Fc alpha R molecules directly implicates these receptors in amplification and regulation of the inflammatory process occurring during IgA-mediated host defence.
Impaired Fc alpha receptor expression is linked to increased immunoglobulin A levels and disease progression in HIV-1-infected patients.
OBJECTIVES: Expression of immunoglobulin (Ig) A Fc receptors (Fc alpha R) and their saturation by endogenous IgA were studied on blood monocytes and neutrophils to evaluate the role of Fc alpha R in the formation of increased serum levels of IgA and IgA-immune complexes (IgA-IC) observed during HIV-1 infection. METHODS: Peripheral blood samples were obtained from 45 patients at different stages of HIV-1 infection and from 22 healthy volunteers. This study was performed using a quantitative flow cytometry method in which blood cells were stained with anti-Fc alpha R monoclonal antibodies (MAb) recognizing epitopes outside the IgA-binding site and with F(ab')2 fragments of anti-IgA antibodies. Immunoprecipitations of radiolabelled surface Fc alpha R molecules were analysed by sodium dodecylsulphate-polyacrylamide gel electrophoresis under glycosylated and deglycosylated conditions. RESULTS: This study reveals a diminished surface expression of Fc alpha R on blood monocytes of HIV-1-infected patients, which follows disease progression. Fc alpha R molecules on patients' neutrophils have a higher apparent molecular mass (60-90 kD) with normal protein core, suggesting expression of receptors with altered carbohydrate moieties. Increased levels of serum IgA significantly correlate with decreased levels of Fc alpha R in HIV-1-infected patients. Surface Fc alpha R molecules are saturated by endogenous IgA1 in both cell types. CONCLUSION: These findings suggest that defective expression and/or altered glycosylation of Fc alpha R may result in receptor saturation, impairment of IgA catabolism and diminished clearance of IgA-IC in HIV-1-infected patients. Fc alpha R expression represents a new marker for disease progression.
Quantitative analysis of glutamate decarboxylase (GAD 65) gene expression in NOD mouse pancreas.
Glutamate decarboxylase (GAD), especially the GAD 65 isoform, is a major autoantigen in autoimmune diabetes. To determine the role of GAD 65 in the pathogenesis of the disease, we developed a quantitative PCR method allowing to establish the absolute number of GAD 65 mRNA molecules expressed in pancreas of male and female non-obese diabetic (NOD) mice at 5 weeks of age, in comparison of the 2 non autoimmune mouse strains. It appeared that pancreatic expression of GAD was similar in the 3 strains (around 30,000 molecules/micrograms total RNA) in males. However, in the NOD mouse, sexual dimorphism was observed with low GAD 65 expression in the female known to show higher incidence of the disease than the male. This finding could contribute to the absence of GAD 65 tolerance in the female and suggests an hormonal control of GAD 65 gene expression.
Systemic chimerism in cadaveric kidney allograft recipients.
Explore the source record for details and available documents.
Peripheral microchimerism in long-term cadaveric-kidney allograft recipients.
Microchimerism after allogeneic organ transplantation may be a mechanism for induction of donor-specific graft acceptance. However, the frequency of chimerism and its relevance in long-term tolerance are uncertain. We studied 15 long-surviving (more than 20 years) cadaveric-kidney transplant recipients for the systemic presence of donor alleles with allele-specific genomic amplification of DRB1 and H-Y loci. Microchimerism was observed in 1 case in peripheral blood and in 4 cases in skin. Chimerism and number of HLA alleles shared by donor and recipient were not correlated. This low frequency of microchimerism in long-term kidney allograft recipients raises doubts about a major participation of chimerism in donor-specific tolerance.
Involvement of human muscle acetylcholine receptor alpha-subunit gene (CHRNA) in susceptibility to myasthenia gravis.
The muscle acetylcholine receptor is the major target of the autoimmune response in generalized myasthenia gravis. To investigate the role of the gene encoding the alpha subunit of the receptor (CHRNA), two stable polymorphic d[(GT).(CA)]dinucleotide repeats, designated HB and BB, were characterized within the first intron of CHRNA. The HB*14 allele conferred a relative risk for myasthenia gravis of 2.5 in 81 unrelated patients compared with 100 control subjects. Very significantly, family analysis based on haplotype segregation data indicated that parental haplotypes associated with HB*14 always segregated to the child with myasthenia gravis (P < 0.0002 for the comparison with the transmission of haplotypes not bearing HB*14), whereas their transmission to unaffected siblings was equilibrated. Myasthenia gravis patients also showed a high frequency of microsatellite variants unseen in controls. These findings implicate the CHRNA in susceptibility to myasthenia gravis.
Anti-CD3 antibody induces long-term remission of overt autoimmunity in nonobese diabetic mice.
Anti-CD3 monoclonal antibodies suppress immune responses by transient T-cell depletion and antigenic modulation of the CD3/T-cell receptor complex. Anti-CD3 treatment of adult nonobese diabetic (NOD) mice, a spontaneous model of T-cell-mediated autoimmune insulin-dependent diabetes mellitus, significantly inhibits the autoimmune process. Short-term low-dose anti-CD3 treatment (5 micrograms/day i.v. for 5 consecutive days) prevented the occurrence of an accelerated form of the disease induced by cyclophosphamide. More unexpectedly, when applied to adult NOD females within 7 days of the onset of full-blown diabetes, the same anti-CD3 regimen induced a complete remission of overt disease (i.e., a return to permanent normoglycemia) in 64-80% of mice. This remission was durable (> 4 months) and was not associated with the disappearance of insulitis (mononuclear cell infiltration of the islets). The immunosuppression was apparently specific for beta-cell-associated antigens, since mice showing anti-CD3-induced remission rejected histoincompatible skin grafts normally, whereas they did not destroy syngeneic islet grafts, unlike control untreated overtly diabetic NOD females. These results open major therapeutic perspectives. They strongly suggest that self-tolerance can be restored in adult mice once autoimmunity is fully established and confirm that this effect can be obtained by transient targeting of the CD3/T-cell receptor without massive T-cell debulking.
The meiosis-specific Xmr gene product is homologous to the lymphocyte Xlr protein and is a component of the XY body.
The Xlr (X-chromosome linked, lymphocyte regulated) multigene family was previously found to determine, in the lymphoid cell lineage, the stage-specific expression of a nuclear protein with a primary sequence suggestive of a transcriptional activator function. We report here the characterization of a second functional member of the Xlr gene family that is abundantly transcribed in testis in a tissue-specific and developmentally regulated manner. The protein product of this newly identified gene, called Xmr (Xlr-related, meiosis regulated), is located in the nuclei of spermatocytes, early in the prophase of the first meiotic division, and later becomes concentrated in the XY nuclear subregion where it is in particular associated with the axes of sex chromosomes. The Xmr protein provides a new tool for the investigation of sex chromosome behaviour during meiosis in mammals.
Nucleosome-restricted antibodies are detected before anti-dsDNA and/or antihistone antibodies in serum of MRL-Mp lpr/lpr and +/+ mice, and are present in kidney eluates of lupus mice with proteinuria.
OBJECTIVE: To compare the humoral response to nucleosomes with the response to their individual components (double-stranded DNA [dsDNA] and histones) and to assess the involvement of antinucleosome antibodies in immune deposits in the kidney of MRL mice. METHODS: We used enzyme-linked immunosorbent assays of sera and kidney eluates for antibody activity against purified nucleosomes, dsDNA, and histones. RESULTS: Antinucleosome antibodies emerged before anti-dsDNA and antihistone antibodies. A fraction of antinucleosome antibodies reacted exclusively with nucleosomes and not with their components, dsDNA and histones. These nucleosome-restricted antibodies were detected in the proteinuric MRL mouse kidney eluate. CONCLUSION: Our findings support the notion that nucleosomes play a major role in the emergence of antinuclear autoantibodies and that antinucleosome antibodies might be involved in the nephritogenic process in murine lupus.
Genetic analysis of immune dysfunction in non-obese diabetic (NOD) mice: mapping of a susceptibility locus close to the Bcl-2 gene correlates with increased resistance of NOD T cells to apoptosis induction.
The non-obese diabetic (NOD) mouse strain provides a remarkable model for investigating the mechanisms of autoimmunity. Independent genetic analyses of this model have previously shown that chromosome 1-linked loci were involved in the control of periinsulitis and sialitis on the one hand and of insulitis and diabetes on the other hand. In the present work, analysis of a [NOD x (NOD x C57BL/6)F1] backcross progeny allowed us to clearly dissociate two genetic regions: one was associated with periinsulitis and mapped to the middle region of chromosome 1, in the vicinity of the Bcl-2 gene; the other was associated with insulitis and mapped to the proximal part of the chromosome. Three intermediate markers D1Mit18, D1Mit5 and D1Mit19 covering at least 25 centiMorgans between these two regions, were associated with neither periinsulitis nor insulitis. The role of the Bcl-2-linked region in the immune anomalies of NOD mice was further investigated in a (NOD x C57BL/6)F2 cross where the Bcl-2nod haplotype was linked to elevated serum levels of IgG (p < 0.0005). The middle region of chromosome 1 is, therefore, involved in the control of three phenotypes, including periinsulitis, sialitis and hyperIgG, pointing to Bcl-2 as a good candidate for a cause of the NOD mouse disease. Consistent with the anti-apoptotic function of the Bcl-2 gene product, activated T lymphocytes from NOD mice showed a markedly increased resistance to induction of apoptosis following deprivation of interleukin-2 when compared to those from non-autoimmune strains. After the recent observation of the Fas gene alterations in the lpr and lprcg mutations, these findings indicate that deregulation of lymphoid cell apoptosis may be a general pathogenetic mechanism in autoimmune diseases.