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Alberto Pugliese

Publications and source records attributed to Alberto Pugliese.

15 recordsLinked to original sources
PubMed2006

A genetic explanation for the rising incidence of type 1 diabetes, a polygenic disease.

We had earlier hypothesized, if parents originated from previously isolated populations that had selected against different critical susceptibility genes for a polygenic disease, their offspring could have a greater risk of that disease than either parent. We therefore studied parents of patients with type 1 diabetes (T1D). We found that parents who transmitted HLA-DR3 to HLA-DR3/DR4 patients had different HLA-A allele frequencies on the non-transmitted HLA haplotype than HLA-DR4-transmitters. HLA-DR3-positive parents also had different insulin (INS) gene allele frequencies than HLA-DR4-positive parents. Parent pairs of patients had greater self-reported ethnicity disparity than parent pairs in control families. Although there was an excess of HLA-DR3/DR4 heterozygotes among type 1 diabetes patients, there were significantly fewer HLA-DR3/DR4 heterozygous parents of patients than expected. These findings are consistent with HLA-DR and INS VNTR alleles marking both disease susceptibility and separate Caucasian parental subpopulations. Our hypothesis thus explains some seemingly disconnected puzzling phenomena, including (1) the rising world-wide incidence of T1D, (2) the excess of HLA-DR3/DR4 heterozygotes among patients, (3) the changing frequency of HLA-DR3/DR4 heterozygotes and of susceptibility alleles in general in patients over the past several decades, and (4) the association of INS alleles with specific HLA-DR alleles in patients with T1D.

Diabetes Mellitus, Type 1↗
PubMed2005

Dendritic cells in human thymus and periphery display a proinsulin epitope in a transcription-dependent, capture-independent fashion.

The natural expression of tissue-specific genes in the thymus, e.g., insulin, is critical for self-tolerance. The transcription of tissue-specific genes is ascribed to peripheral Ag-expressing (PAE) cells, which discordant studies identified as thymic epithelial cells (TEC) or CD11c+ dendritic cells (DC). We hypothesized that, consistent with APC function, PAE-DC should constitutively display multiple self-epitopes on their surface. If recognized by Abs, such epitopes could help identify PAE cells to further define their distribution, nature, and function. We report that selected Abs reacted with self-epitopes, including a proinsulin epitope, on the surface of CD11c+ cells. We find that Proins+ CD11c+ PAE cells exist in human thymus, spleen, and also circulate in blood. Human thymic Proins+ cells appear as mature DC but express CD8alpha, CD20, CD123, and CD14; peripheral Proins+ cells appear as immature DC. However, DC derived in vitro from human peripheral blood monocytes include Proins+ cells that uniquely differentiate and mature into thymic-like PAE-DC. Critically, we demonstrate that human Proins+ CD11c+ cells transcribe the insulin gene in thymus, spleen, and blood. Likewise, we show that mouse thymic and peripheral CD11c+ cells transcribe the insulin gene and display the proinsulin epitope; moreover, by using knockout mice, we show that the display of this epitope depends upon insulin gene transcription and is independent of Ag capturing. Thus, we propose that PAE cells include functionally distinct DC displaying self-epitopes through a novel, transcription-dependent mechanism. These cells might play a role in promoting self-tolerance, not only in the thymus but also in the periphery.

Animals↗
PubMed2005

Thymic expression of peripheral tissue antigens in humans: a remarkable variability among individuals.

The majority of maturing T lymphocytes that recognize self-antigens is eliminated in the thymus upon exposure to their target antigens. This physiological process of negative selection requires that tissue-specific antigens be expressed by thymic cells, a phenomenon that has been well studied in experimental animals. Here, we have examined the expression in human thymi of four retinal antigens, that are capable of inducing autoimmune ocular disease retinal S-antigen (S-Ag), recoverin, RPE65 and inter-photoreceptor retinoid-binding protein (IRBP)], as well as four melanocyte-specific antigens, two of which are used as targets for melanoma immunotherapy [gp100, melanoma antigen recognized by T cells 1, tyrosinase-related protein (TRP)-1 and TRP-2]. Using reverse transcription (RT)-PCR, we found that all thymic samples from the 18 donors expressed mRNA transcripts of most or all the eight tested tissue antigens. Yet, the expression of the transcripts varied remarkably among the individual thymic samples. In addition, S-Ag, RPE65 and IRBP were detected by immunostaining in rare cells in sections of human thymi by antibodies against these proteins. Quantitative real-time RT-PCR analysis revealed that the retinal antigen transcripts in the human thymus are present at trace levels, that are lower by approximately five orders of magnitude than those in the retina. Our observations thus support the notions that thymic expression is a common feature for all tissue-specific antigens and that the levels of expression play a role in determining the susceptibility to autoimmunity against these molecules.

Antigens, Neoplasm↗
PubMed2005

The insulin gene in type 1 diabetes.

Insulin is a key autoantigen in the autoimmune process leading to the development of type 1 diabetes. Recent studies in both humans and mice have shown that variation in the expression of the insulin gene, in the thymus rather than the pancreas, contributes to disease susceptibility by affecting self-tolerance to insulin. These findings have brought about a paradigm-shift in our understanding of self-tolerance and autoimmunity to molecules with tissue-restricted expression, which are often the target of autoimmune disease.

Animals↗
PubMed2005

Islet transplantation in type 1 diabetes mellitus using cultured islets and steroid-free immunosuppression: Miami experience.

Following the success obtained with transplantation of fresh human islets under steroid-free immunosuppression, this trial evaluated the transplantation of islets that had undergone a period of in vitro culture and the potential of tumor necrosis factor (TNF-alpha) blockade to improve islet engraftment. Subjects included 16 patients with type 1 diabetes mellitus (T1DM); half were randomly assigned to receive Infliximab immediately preceding initial infusion. Immunosuppression consisted of daclizumab induction and sirolimus/tacrolimus maintenance. Out of 16 subjects 14 achieved insulin independence with one or two islet infusions; adverse events precluded completion in two. Without supplemental infusions, 11/14 (79%) subjects were insulin independent at 1 year, 6/14 (43%) at 18 months; these same subjects remain insulin independent at 33+/-6 months. While on immunosuppression, all patients maintained graft function. Out of 14 patients, 8 suffered chronic partial graft loss, likely immunological in nature, 5 of these received supplemental infusions. Currently, 11 subjects remain on immunosuppression, 8 (73%) are insulin independent, two with supplemental infusions. Insulin independent subjects demonstrated normalization of HbA1c, fructosamine and Mean Amplitude of Glycemic Excursions (MAGE) values. No clinical benefit of infliximab was identified. These results demonstrate that transplantation of cultured human islet allografts results in reproducible insulin independence in all subjects under this immunosuppressive regimen, comparable to that of freshly transplanted islets (Edmonton protocol).

Adult↗
PubMed2004

Peripheral antigen-expressing cells in type 1 diabetes.

Studies in both humans and rodent models provide new insight into key mechanisms regulating tolerance to self-molecules. There is evidence that tissue-specific molecules are expressed in the thymus and peripheral lymphoid tissues (PLTs) by specialized antigen-presenting cells (APCs), and that such expression is critical for self-tolerance. Insulin, a key hormone exclusively produced by pancreatic beta cells and a critical autoantigen in type 1 diabetes, provides an excellent example of a molecule with tissue-restricted expression that is ectopically expressed by APCs in both thymus and PLTs. APCs may play a role in insulin presentation in both the central and peripheral immune system. Functional data from several transgenic and knockout mouse models, some specific for the expression of insulin, help dissect the significance of self-molecule presentation by APCs and its role in autoimmune diabetes.

Animals↗
PubMed2004

Central and peripheral autoantigen presentation in immune tolerance.

Recent studies in both humans and experimental rodent models provide new insight into key mechanisms regulating tolerance to self-molecules. These recent advances are bringing about a paradigm shift in our views about tolerance to self-molecules with tissue-restricted expression. There is, indeed, mounting evidence that selected antigen-presenting cells (APCs) have the ability to synthesize and express self-molecules, and that such expression is critical for self-tolerance. Insulin is a key hormone produced exclusively by pancreatic beta-cells and a critical autoantigen in type 1 diabetes. It provides an excellent example of a molecule with tissue-restricted expression that is expressed ectopically by APCs. The fact that APCs expressing insulin have been demonstrated in both thymus and peripheral lymphoid tissues suggests that they may play a role in insulin presentation in both the central and peripheral immune system. Experimental mice, in which insulin expression was altered, provide functional data that help to dissect the role of insulin presentation by APCs of the immune system. This review addresses recent literature and emerging concepts about the expression of self-molecules in the thymus and peripheral lymphoid tissues and its relation to self-tolerance.

Animals↗
PubMed2004

Transient chylomicronemia preceding the onset of insulin-dependent diabetes in a young girl with no humoral markers of islet autoimmunity.

OBJECTIVE: We investigated the possible causes of diabetes in a young child who presented with hyperglycemia associated with severe hypertriglyceridemia (>166 mmol/l), hypercholesterolemia (>38 mmol/l) and fasting chilomicrons. RESULTS: The patient did not have any of the HLA and autoantibody markers typically associated with type 1 diabetes. A glucose clamp failed to demonstrate insulin resistance (peripheral glucose utilization rate (M)=4.3 mg/kg per min) and there was no family history of type 2 diabetes or maturity onset diabetes in youth. Both fasting and stimulated C-peptide levels, including those in response to i.v. glucagon, were below the limit of detection. This is consistent with loss of beta-cell function. The family history did not reveal the existence of relatives with lipid abnormalities, coronary heart disease, and pancreatitis. We did not find any abnormality of plasma apoCII, lipoproteinlipase and hepatic lipase activities. The patients had a epsilon3/epsilon3 apoE genotype and she rapidly cleared an oral fat load after normalization of plasma lipids. CONCLUSIONS: The mild hyperglycemia seems an unlikely explanation for both the severe hypertriglyceridemia and chylomicronemia. A more plausible explanation is transient lipoproteinlipase deficiency. This rare condition, occasionally associated with a high-fat diet, could have caused the rapid and dramatic hypertriglyceridemia observed in this patient, which in turn might have led to the beta-cell destruction by direct lipid toxicity.

Autoantibodies↗
PubMed2002

Real-time sequence-specific primer polymerase chain reaction amplification of HLA class II alleles: a novel approach to analyze microchimerism.

The careful assessment of microchimerism is essential to investigate the effects of donor bone marrow-derived cells in transplantation. We have developed a protocol to assess microchimerism based on the HLA mismatch between the recipient and the donor. Our approach combines real-time polymerase chain reaction (PCR) with sequence-specific primer PCR (SSP-PCR) to selectively amplify and measure the abundance of donor HLA alleles in DNA samples extracted from the recipient after transplant. To optimize and validate the reliability of this method at different levels of microchimerism, we tested serial dilutions of donor DNA into recipient DNA. We demonstrate that donor alleles can be readily detected and reliably measured at concentrations as low as 0.1%. This method is simple and rapid and could find practical application in the assessment of microchimerism in patients receiving organ or cellular transplants in conjunction with donor bone marrow cells infusion.

Alleles↗
PubMed2002

Peripheral antigen-expressing cells and autoimmunity.

There is growing evidence that self-molecules with tissue-restricted expression are also expressed at low levels in the thymus, where such expression may affect the development of self-tolerance. Genetic factors may modulate such expression and, in turn, influence susceptibility to autoimmune responses against specific molecules. Contrasting reports exist regarding the phenotype of the cells that express self-molecules in the thymus. Indeed, both bone marrow derived antigen-presenting cells and thymic epithelial cells were reported to express self-molecules with tissue-restricted expression. Further studies of these cells and the mechanisms by which they exert their putative tolerogenic effects clearly are necessary.

Autoantigens↗
PubMedDate not supplied

The insulin gene in diabetes.

Lack of insulin production or abnormalities affecting insulin secretion are key to the development of almost all forms of diabetes, including the common type 1 (insulin-dependent) and type 2 (non-insulin-dependent) diabetes and the more rare forms of maturity-onset diabetes of the young (MODY). Because insulin has such a central role in the pathogenesis of both forms of diabetes, the insulin gene (INS) has always been considered a candidate susceptibility gene. A number of studies have shown that the allelic variation and parent-of-origin effects affect the transmission and expression of the insulin gene in pancreatic beta-cells and extra-pancreatic tissues. These observations have led to the formulation of new hypotheses to explain the biological mechanisms by which functional differences in the expression of the insulin gene may contribute to diabetes susceptibility.

Diabetes Mellitus↗