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S K Datta

Publications and source records attributed to S K Datta.

At least 37 records · Page 2Linked to original sources
PubMed1999

Antigen-specific therapy of murine lupus nephritis using nucleosomal peptides: tolerance spreading impairs pathogenic function of autoimmune T and B cells.

In the (SWR x NZB)F1 mouse model of lupus, we previously localized the critical autoepitopes for nephritogenic autoantibody-inducing Th cells in the core histones of nucleosomes at aa positions 10-33 of H2B and 16-39 and 71-94 of H4. A brief therapy with the peptides administered i.v. to 3-mo-old prenephritic (SWR x NZB)F1 mice that were already producing pathogenic autoantibodies markedly delayed the onset of severe lupus nephritis. Strikingly, chronic therapy with the peptides injected into 18-mo-old (SWR x NZB)F1 mice with established glomerulonephritis prolonged survival and even halted the progression of renal disease. Remarkably, tolerization with any one of the nucleosomal peptides impaired autoimmune T cell help, inhibiting the production of multiple pathogenic autoantibodies. However, cytokine production or proliferative responses to the peptides were not grossly changed by the therapy. Moreover, suppressor T cells were not detected in the treated mice. Most interestingly, the best therapeutic effect was obtained with nucleosomal peptide H416-39, which had a tolerogenic effect not only on autoimmune Th cells, but autoimmune B cells as well, because this peptide contained both T and B cell autoepitopes. These studies show that the pathogenic T and B cells of lupus, despite intrinsic defects in activation thresholds, are still susceptible to autoantigen-specific tolerogens.

Animals↗
PubMed1999

Combinatorial interactions regulate cardiac expression of the murine adenylosuccinate synthetase 1 gene.

The mammalian heart begins contracting at the linear tube stage during embryogenesis and continuously pumps, nonstop, throughout the entire lifetime of the animal. Therefore, the cardiac energy metabolizing pathways must be properly established and efficiently functioning. While the biochemistry of these pathways is well defined, limited information regarding the regulation of cardiac metabolic genes is available. Previously, we reported that 1.9 kilobase pairs of murine adenylosuccinate synthetase 1 gene (Adss1) 5'-flanking DNA directs high levels of reporter expression to the adult transgenic heart. In this report, we define the 1.9-kilobase pair fragment as a cardiac-specific enhancer that controls correct spatiotemporal expression of a reporter similar to the endogenous Adss1 gene. A 700-base pair fragment within this region activates a heterologous promoter specifically in adult transgenic hearts. Proteins present in a cardiac nuclear extract interact with potential transcription factor binding sites of this region and these cis-acting sites play important regulatory roles in the cardiac expression of this reporter. Finally, we report that several different cardiac transcription factors trans-activate the 1.9HSCAT construct through these sites and that combinations result in enhanced reporter expression. Adss1 appears to be one of the first target genes identified for the bHLH factors Hand1 and Hand2.

Adenylosuccinate Synthase↗
PubMed1999

Regulation of forestomach-specific expression of the murine adenosine deaminase gene.

The maturation of stratified squamous epithelium of the upper gastrointestinal tract is a highly ordered process of development and differentiation. Information on the molecular basis of this process is, however, limited. Here we report the identification of the first murine forestomach regulatory element using the murine adenosine deaminase (Ada) gene as a model. In the adult mouse, Ada is highly expressed in the terminally differentiated epithelial layer of upper gastrointestinal tract tissues. The data reported here represent the identification and detailed analysis of a 1. 1-kilobase (kb) sequence located 3.4-kb upstream of the transcription initiation site of the murine Ada gene, which is sufficient to target cat reporter gene expression to the forestomach in transgenic mice. This 1.1-kb fragment is capable of directing cat reporter gene expression mainly to the forestomach of transgenic mice, with a level comparable to the endogenous Ada gene. This expression is localized to the appropriate cell types, confers copy number dependence, and shows the same developmental regulation. Mutational analysis revealed the functional importance of multiple transcription factor-binding sites.

Adenosine Deaminase↗
PubMed1999

Major peptide autoepitopes for nucleosome-specific T cells of human lupus.

We tested 154 peptides spanning the entire length of core histones of nucleosomes for the ability to stimulate an anti-DNA autoantibody-inducing T helper (Th) clone, as well as CD4(+) T-cell lines and T cells, in fresh PBMCs from 23 patients with lupus erythematosus. In contrast to normal T cells, lupus T cells responded strongly to certain histone peptides, irrespective of the patient's disease status. Nucleosomal peptides in histone regions H2B(10-33), H4(16-39) (and overlapping H4(14-28)), H4(71-94), and H3(91-105) (and overlapping H3(100-114)) were recurrently recognized by CD4 T cells from the patients with lupus. Remarkably, these same peptides overlap with major epitopes for the Th cells that induce anti-DNA autoantibodies and nephritis in lupus-prone mice. We localized 2 other recurrent epitopes for human lupus T cells in H2A(34-48) and H4(49-63). All the T-cell autoepitopes have multiple HLA-DR binding motifs, and the epitopes are located in histone regions recognized by lupus autoantibodies, suggesting a basis for their immunodominance. Native nucleosomes and their peptides H4(16-39), H4(71-94), and H3(91-105) induced a stronger IFN-gamma response, whereas others, particularly, H2A(34-48), favored an IL-10- and/or IL-4-positive T-cell response. The major autoepitopes may reveal the mechanism of autoimmune T-cell expansion and lead to antigen-specific therapy of human lupus.

Adolescent↗
PubMed1998

Anti-CD40 ligand antibody treatment of SNF1 mice with established nephritis: preservation of kidney function.

Prior studies have demonstrated that treatment of young, prenephritic lupus-prone mice with Ab directed against CD40 ligand (CD40L) prolongs survival and decreases the incidence of severe nephritis. In this report, we show that for (SWR x NZB)F1 (SNF1) animals with established lupus nephritis, long-term treatment with anti-CD40L beginning at either 5.5 or 7 mo of age prolonged survival and decreased the incidence of severe nephritis. "Older" mice were chosen for these studies to more closely resemble the clinical presentation of patients with established renal disease. We show that age at the start of treatment, which typically correlates with severity of disease, is an important factor when determining an efficacious therapeutic protocol since animals that began treatment at 7 mo of age required a more aggressive treatment protocol than animals at 5.5 mo of age. Remarkably, several anti-CD40L-treated animals beginning treatment at age 5.5 mo demonstrated a decline in proteinuria, as opposed to increasing proteinuria levels seen in hamster IgG (HIg)-treated controls, and histologic examination of kidneys from anti-CD40L-treated mice revealed dramatically diminished inflammation, sclerosis/fibrosis, and vasculitis, in marked contrast to the massive inflammation and kidney destruction observed in control animals that received hamster IgG. Spleens from anti-CD40L-treated mice also exhibited markedly reduced inflammation and fibrosis compared with controls. Together, these results show that treatment of older, nephritic SNF1 animals with long-term anti-CD40L immunotherapy significantly prolongs survival, reduces the severity of nephritis, and diminishes associated inflammation, vasculitis, and fibrosis.

Age Factors↗
PubMed1998

Adenosine deaminase-deficient mice generated using a two-stage genetic engineering strategy exhibit a combined immunodeficiency.

Adenosine deaminase (ADA) deficiency in humans leads to a combined immunodeficiency. The mechanisms involved in the lymphoid specificity of the disease are not fully understood due to the inaccessibility of human tissues for detailed analysis and the absence of an adequate animal model for the disease. We report the use of a two-stage genetic engineering strategy to generate ADA-deficient mice that retain many features associated with ADA deficiency in humans, including a combined immunodeficiency. Severe T and B cell lymphopenia was accompanied by a pronounced accumulation of 2'-deoxyadenosine and dATP in the thymus and spleen, and a marked inhibition of S-adenosylhomocysteine hydrolase in these organs. Accumulation of adenosine was widespread among all tissues examined. ADA-deficient mice also exhibited severe pulmonary insufficiency, bone abnormalities, and kidney pathogenesis. These mice have provided in vivo information into the metabolic basis for the immune phenotype associated with ADA deficiency.

Adenosine↗
PubMed1998

Promiscuous presentation and recognition of nucleosomal autoepitopes in lupus: role of autoimmune T cell receptor alpha chain.

T cells specific for nucleosomal autoepitopes are selectively expanded in lupus mice and these Th cells drive autoimmune B cells to produce pathogenic antinuclear antibodies. We transfected the TCR-alpha and -beta chain genes of a representative, pathogenic autoantibody-inducing Th clone specific for the nucleosomal core histone peptide H471-94 into TCR-negative recipient cells. Although the autoimmune TCRs were originally derived from SNF1 (I-Ad/q) mice, the transfectants could recognize the nucleosomal autoepitope presented by APC-bearing I-A molecules of all haplotypes tested, as well as human DR molecules. Competition assays indicated that the autoepitopes bound to the MHC class II groove. Most remarkably, MHC-unrestricted recognition of the nucleosomal peptide epitope was conferred by the lupus TCR-alpha chain even when it paired with a TCR-beta chain of irrelevant specificity. Several other disease-relevant Th clones and splenic T cells of lupus mice had similar properties. The TCR-alpha chains of these murine lupus Th clones shared related motifs and charged residues in their CDRs, and similar motifs were apparent even in TCR-alpha chains of human lupus Th clones. The lupus TCR-alpha chains probably contact the nucleosomal peptide complexed with MHC with relatively high affinity/avidity to sustain TCR signaling, because CD4 coreceptor was not required for promiscuous recognition. Indeed, pathogenic autoantibody-inducing, CD4-negative, TCR-alphabeta+ Th cells are expanded in systemic lupus erythematosus. These results have implications regarding thymic selection and peripheral expansion of nucleosome-specific T cells in lupus. They also suggest that universally tolerogenic epitopes could be designed for therapy of lupus patients with diverse HLA alleles. We propose to designate nucleosomes and other antigens bearing universal epitopes "Pantigens" (for promiscuous antigens).

Amino Acid Sequence↗
PubMed1998

Management of choroidal metastasis: a report.

Cancers metastatic to the eye are the most common intraocular malignancy, the choroid being the most common site of affection. Breast and lung cancers are the two most common malignancies metastatic to the eye. Patients usually present with diminished visual acuity of field loss. Management of these cases is very gratifying with a large majority of patients showing resolution and maintenance of useful vision in the involved eye. This communication presents our experience in management of a case of choroidal metastasis from a breast primary. A combination of radiotherapy and chemotherapy lead to complete resolution of the lesion with no recurrences in a follow-up of over 6 months.

Angiography↗
PubMed1998

Production of pathogenic antibodies: cognate interactions between autoimmune T and B cells.

A select population of autoimmune T-helper (T(H)) cells drive the production of pathogenic anti-DNA autoantibodies in SLE. These T(H) cells recognize nucleosomal peptides that are processed and presented by the anti-DNA B cells that they help. The critical peptide epitopes for the T(H) cells reside in the core histones of the nucleosome particle. Remarkably, the nucleosomal peptide epitopes do not obey the rule of MHC-restriction; they can be promiscuously presented and recognized in the context of diverse MHC alleles. Such promiscuous antigens, called pantigens, are also recognized by autoimmune T cells, in a degenerate fashion, and this promiscuous recognition is conferred by the lupus TCR alpha chains. High-affinity interactions between the lupus TCRs and MHC-nucleosomal peptide complex due to reciprocally charged residues probably overcome the requirement for MHC restriction. These studies open up the possibility of developing 'universally' tolerogenic epitopes for therapy of lupus in humans despite their diversity of HLA alleles. The results also have profound implications regarding the selection of autoimmune T cells in the lupus-prone thymus and their expansion in the periphery. Furthermore, the T(H) cells, as well as B cells of lupus, have a regulatory defect causing markedly increased and prolonged expression of CD40 ligand (CD40L), which mediates abnormal co-stimulatory signals to autoimmune B cells, sustaining the production of pathogenic autoantibodies. These observations suggest a new paradigm for B cell hyperactivity in lupus and provide alternative targets for immunotherapy. Indeed, giving only three injections of anti-CD40L antibody in a one-week period to mice with manifest lupus selectively blocks the pathogenic autoimmune response and delays the development of lupus nephritis by one year (equivalent to three decades in humans). Thus, possession of promiscuous, high-affinity receptors and prolonged expression of CD40L by lupus T cells probably lowers activation threshold, leading to an autoimmune response against nucleosomes derived from apoptotic cells that are normally ignored by the immune system.

Animals↗
PubMed1997

Diverse genetic regulatory motifs required for murine adenosine deaminase gene expression in the placenta.

Murine adenosine deaminase (ADA) is a ubiquitous purine catabolic enzyme whose expression is subject to developmental and tissue-specific regulation. ADA is enriched in trophoblast cells of the chorioallantoic placenta and is essential for embryonic and fetal development. To begin to understand the genetic pathway controlling Ada gene expression in the placenta, we have identified and characterized a 770-base pair fragment located 5.4 kilobase pairs upstream of the Ada transcription initiation site, which directs reporter gene expression to the placenta of transgenic mice. The expression pattern of the reporter gene reflected that of the endogenous Ada gene in the placenta. Sequence analysis revealed potential binding sites for bHLH and GATA transcription factors. DNase I footprinting defined three protein binding regions, one of which was placenta-specific. Mutations in the potential protein binding sites and footprinting regions resulted in loss of placental expression in transgenic mice. These findings indicate that multiple protein binding motifs are necessary for Ada expression in the placenta.

Adenosine Deaminase↗
PubMed1997

T cells of lupus and molecular targets for immunotherapy.

A major advance in understanding the basic mechanism driving the pathogenic autoimmune response in SLE has been the identification of nucleosome as a primary immunogen. The production of pathogenic antinuclear antibodies in SLE is mediated by a MHC class II restricted, cognate interaction between select populations of autoimmune T helper cells and autoimmune B cells that recognize epitopes in the different molecular components of the nucleosome particle: a form of intermolecular-intrastructural help. In the SNF1 model, we have localized the critical peptide autoepitopes for lupus nephritis-inducing Th cells in the core histones of nucleosomes, at amino acid positions 10-33 of H-2B and 16-39 and 71-94 of H4. Remarkabely, the nephritogenic epitopes are located in the regions of histones that are also targeted by lupus B cells, as well as the sites where the histones contact DNA in the nucleosome, indicating that they are specially protected during antigen processing. Identification of the peptide epitopes is a basic step toward defining how the pathogenic Th cells emerge in lupus. In addition, we found that the pathogenic Th cells and B cells of lupus have a regulatory defect in the expression of CD40 ligand (CD40L or gp39), which results in abnormal costimulatory signals that sustain the production of pathogenic autoantibodies. Specific immunotherapy that blocks the pathogenic T and B cell interaction in lupus can be designed based on the knowledge of these disease mechanisms.

Animals↗
PubMed1996

Structure and expression of the murine muscle adenylosuccinate synthetase gene.

A muscle-specific isoform of adenylosuccinate synthetase (AdSS1, EC) is one of three enzymes that constitute the purine nucleotide cycle, a muscle-specific metabolic cycle. Previously, we showed that the muscle Adss1 gene was highly expressed in both skeletal muscle and heart of the adult mouse. Here we have shown that the Adss1 gene is initially activated early in embryonic development in skeletal muscle and heart precursors and is subsequently up-regulated perinatally. The earliest detectable gene expression corresponds with the establishment of the first myogenic and cardiac lineages. To allow identification of the genetic signals controlling this developmental pattern of expression, the Adss1 gene was cloned and its structure determined. Transgenic analysis has shown that 1.9 kilobase pairs of 5' flank can activate expression in skeletal muscle progenitors and direct enhanced expression to adult cardiac muscle. Sequence analysis of the promoter and 5' flanking region revealed the presence of numerous potential muscle-specific cis-regulatory elements.

Adenine Nucleotides↗
PubMed1996

Metabolic and immunologic consequences of limited adenosine deaminase expression in mice.

Adenosine deaminase (ADA; EC 3.5.4.4) deficiency in humans is an autosomal recessive genetic disorder that results in severe combined immunodeficiency disease. ADA-deficient mice generated by targeted gene disruption die perinatally, preventing postnatal analysis of ADA deficiency. We have recently rescued ADA-deficient fetuses from perinatal lethality by expression of an ADA minigene in the placentas of ADA-deficient fetuses, thus generating postnatal mice admissible to analysis of ADA deficiency. The minigene used also directed ADA expression to the forestomach postnatally, producing adult animals that lacked ADA enzymatic activity in all tissues outside the gastrointestinal tract. Mice with limited ADA expression exhibited profound disturbances in purine metabolism, including thymus-specific accumulations of deoxyadenosine and dATP, and inhibition of S-adenosylhomocysteine hydrolase in the thymus, spleen, and, to a lesser extent, the liver. Lymphopenia and mild immunodeficiency were associated with these tissue-specific metabolic disturbances. These mice represent the first genetic animal model for ADA deficiency and provide insight into the tissue-specific requirements of ADA.

Adenosine Deaminase↗
PubMed1996

Nucleosomal peptide epitopes for nephritis-inducing T helper cells of murine lupus.

Nucleosome-specific T helper (Th) cells provide major histocompatibility complex class II-restricted, cognate help to nephritogenic antinuclear autoantibody-producing B cells in lupus. However, the lupus Th cells do not respond when components of the nucleosome, such as free DNA or histones, are individually presented by antigen-presenting cells. Thus critical peptide epitopes for the pathogenic Th cells are probably protected during uptake and processing of the native nucleosome particle as a whole. Therefore, herein we tested 145 overlapping peptides spanning all four core histones in the nucleosome. We localized three regions in core histones, one in H2B at amino acid position 10-33 (H2B(10-33)), and two in H4, at position 16-39 (H4(16-39)) and position 71-94 (H4(71-94)), that contained the peptide epitopes recognized by the pathogenic autoantibody-inducing Th cells of lupus. The peptide autoepitopes also triggered the pathogenic Th cells of (SWR x NZB)F1 lupus mice in vivo to induce the development of severe lupus nephritis. The nucleosomal autoepitopes stimulated the production of Th1-type cytokines, consistent with immunoglobulin IgG2a, IgG2b, and IgG3 being the isotypes of nephritogenic autoantibodies induced in the lupus mice. Interestingly, the Th cell epitopes overlapped with regions in histones that contain B cell epitopes targeted by autoantibodies, as well as the sites where histones contact with DNA in the nucleosome. Identification of the disease-relevant autoepitopes in nucleosomes will help in understanding how the pathogenic Th cells of spontaneous systemic lupus erythematosus emerge, and potentially lead to the development of peptide-based tolerogenic therapy for this major autoimmune disease.

Amino Acid Sequence↗