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R Sgonc

Publications and source records attributed to R Sgonc.

29 records · Page 2Linked to original sources
PubMed1995

Genomic analysis of collagen and endogenous virus loci in the UCD-200 and 206 lines of chickens, animal models for scleroderma.

University of California at Davis (UCD) lines 200 and 206 chickens develop a hereditary systemic scleroderma-like connective tissue disease characterized by severe lymphocytic infiltration and excessive accumulation of collagen in skin and internal organs. The immune system seems to play an important role in the development and/or perpetuation of this condition. The main goal of our work with this strain is the investigation of interactions between endothelial cells, lymphocytes, macrophages and fibroblasts leading to the proliferation of the latter and to excessive collagen synthesis and/or deposition. One aim of the present study was to clarify whether UCD-200 and 206 chickens have a defect of collagen genes at the genomic level by means of restriction fragment length polymorphism (RFLP) analysis using non-radioactively labelled cDNA probes specific for chicken alpha 1(I), alpha 2(I), alpha 1(II), alpha 1(III), alpha 1(VI), alpha 2(VI), and alpha 3(VI) (pro) collagens. As in the human disease, no gross alteration at the genomic level of collagen genes has been found, thus providing the UCD-200/206 model to be appropriate for studying the altered collagen metabolism in systemic sclerosis (SSc). In addition to the RFLP analysis of procollagen genes, we investigated the endogenous avian leukosis virus loci (ev) of UCD-200 and 206 chickens by means of Southern blot analysis of Sac I and BamH I digested DNA samples using pRAV-2, a Rous sarcoma virus specific probe, for hybridization. Most UCD-200 and 206 chickens harbour evs 1, 3 and 10 similar to the healthy control UCD-058, but they also contain a novel ev characterized by a 4.2 kb Sac I fragment and a 6.1 kb BamH I fragment, which we would like to designate ev 23. So far, the role of ev 23 in the development of avian scleroderma is unclear; for further analysis classical crossbreeding experiments are necessary and are underway.

Alpharetrovirus↗
PubMed1994

Thymocyte apoptosis induced by elevated endogenous corticosterone levels.

A well-known model of apoptosis is induction in thymocytes by injection of pharmacological doses of exogenous steroids. The aim of this study was to investigate whether this process also occurs under physiological conditions, i.e. by stimulation of endogenous glucocorticoid release, using the chicken as an experimental model. Endogenous glucocorticoid levels can be elevated by immunization with exogenous antigens or by injection of conditioned medium, e.g. supernatant of mitogen-stimulated spleen cells. This effect is mediated by so-called glucocorticoid-increasing factors, and is considered to act as an immunoregulatory principle. Thymocyte DNA of so treated birds showed a typical "ladder" pattern after electrophoresis in a 1.8% agarose gel, and degradation could be prevented by RU 38,486. This provides evidence that apoptosis can be induced by elevating endogenous corticosterone levels in vivo. By means of in situ nick translation (ISNT) and simultaneous immunofluorescence tests, it was possible to analyze various thymic subpopulations during apoptosis after treatment with exogenous glucocorticoids. Additionally, using confocal microscopical techniques, apoptosis of the same cells as analyzed by ISNT is shown. The possible role of elevated concentrations of endogenous glucocorticoids in regulating thymocyte cell death and autoimmune diseases is discussed.

Animals↗
PubMed1994

Methods for the detection of apoptosis.

Apoptosis is central to many basic and clinically oriented investigations, and this article is a brief overview of the most frequently utilized methods for detection of apoptotic cells, including the study of morphology, analysis of DNA degradation, DNA end labeling techniques, flow cytometric analysis, and nuclease assays. Features and advantages of the different methods are discussed.

Animals↗
PubMed1993

Effects of cytokine application on glucocorticoid secretion in an animal model for systemic scleroderma.

We previously reported on an altered immune-endocrine feedback loop via the hypothalamo-pituitary-adrenal (HPA) axis in Obese strain (OS) chickens afflicted with spontaneous autoimmune thyroiditis. These animals are deficient in plasma corticosterone increase after antigenic challenge or application of cytokine-containing conditioned medium of mitogen-stimulated spleen cells (CM). To investigate whether the impaired ability to respond to cytokines with glucocorticoid-increasing factor (GIF) activity, e.g. interleukin 1 (IL 1), is restricted to OS chickens as a model for an organ-specific autoimmune disease, we extended our experiments to another autoimmune-prone animal strain, the chickens of the University of California at Davis line 200 (UCD-200). These animals develop an inherited inflammatory fibrotic disease that closely resembles human progressive systemic sclerosis (scleroderma). Application of GIF-containing CM to UCD-200 chickens leads to a transient increase in glucocorticoid serum levels within 1-2 hours comparable to that of controls. But, while corticosterone levels in the latter returned to normal baseline levels after 4 hours, they were still elevated in autoimmune chickens. Although the peak of the glucocorticoid hormone serum concentrations was equal to that of controls, UCD-200 had to secrete twice as much adrenocorticotropic hormone to achieve this corticosterone serum level due to an apparent hyporesponsiveness of the adrenal gland to this secretagogue. The altered cytokine-induced glucocorticoid secretion is found in early as well as in chronic, sclerotic stages of the disease. Cellular alterations in the peripheral blood of UCD-200 chickens during the prolonged elevated corticosterone section, i.e. between 2-4 hours after CM application, are characterized by a significant decrease in the percentage of CD4+ and CD8+ cells. Furthermore, a significant increase in B cells up to 24 hours with a maximum after 1 hour was found. The proliferative response to the mitogen concanavalin A of peripheral mononuclear cells was inversely correlated to the serum corticosterone level, showing a permanent decrease of 80-90% after 1-4 hours in autoimmune animals. This functional alteration in UCD-200 was accompanied by an 80% decrease in serum interleukin 2 (sIL 2) activity 4 hours after CM application. Twenty-four hours later an eight-fold increase in sIL 2 rebound activity was found, indicating that the inhibitory effect of corticosterone in UCD-200 chickens is not long-lasting.

Adrenocorticotropic Hormone↗
PubMed1992

Frequency of chicken CD4+ and CD8+ cells. Genetic control and effect of Rous sarcoma virus infection.

In chickens from congenic inbred lines CB and CC that differ only in the major histocompatibility complex (MHC), we observed significantly different percentages of CD4+ and CD8+ cells in peripheral blood lymphocytes (PBL) and spleen. Positive cells were detected by indirect immunofluorescence test as analysed by flow cytometry. In both PBL and spleen cell suspensions, the number of CD4+ cells was significantly higher in CB than in CC chickens, whereas in CC birds there was a higher percentage of CD8+ cells than in CB. These statistically significant differences were under the MHC control. We found no statistically significant influence of regressions or progression of Rous sarcoma virus-induced tumours on the percentage of peripheral T cells and on the interleukin-2 production in vitro.

Animals↗
PubMed1991

Phenotypic analysis of skin infiltrates in comparison with peripheral blood lymphocytes, spleen cells and thymocytes in early avian scleroderma.

University of California at Davis line 200 (UCD-200) chickens develop a hereditary connective tissue disease characterized by severe lymphocytic infiltration, vascular occlusion and fibrosis of skin and internal organs. To identify cellular immunological abnormalities in the acute inflammatory disease stage of this animal model for progressive systemic sclerosis (PSS) we investigated the phenotypic characteristics and function of peripheral blood lymphocytes (PBL), spleen cells and thymocytes in comparison with skin infiltrating cells. Immunofluorescence and immunohistochemical analysis using monoclonal antibodies revealed the overwhelming majority of skin infiltrating mononuclear cells in the deeper dermis and subcutaneous tissue to be T cell receptor alpha/beta (TcR2)+/CD3+/CD4+/class II+ cells, a small portion (5-10%) of which were interleukin 2 (IL-2) receptor positive. In contrast, the inflammatory infiltrate in perivascular areas of the papillary dermis was constituted of mainly TcR gamma/delta (TcR1)+/class II- lymphocytes. Only few B cells (T/B cell ratio greater than 5) were detected. These diseased chickens showed significantly reduced percentages and numbers of circulating peripheral T cells exhibiting TcR1, TcR2, CD3, CD4 or IL-2-receptor, probably owing to an increased influx into lymphoid organs and affected tissues. In contrast to healthy chickens, the thymi of UCD-200 animals revealed fewer cells expressing TcR1, TcR2 and class II antigen, suggesting an altered intrathymic maturation of the T cell lineage. Functional in vitro studies showed a significantly decreased T cell mitogen-induced proliferation rate associated with a decreased capacity to produce IL-2 and to express IL-2 receptors. In contrast to the deficient in vitro IL-2 production the sera of UCD-200 chickens contained significant levels of IL-2 bioactivity. The alteration of T lymphocyte physiology in UCD-200 chickens adds, at least in part, to the parallels between this animal model and its human counterpart. These data confirm our hypothesis that the PSS-like disease of UCD-200 chickens includes a numeric and/or functional alteration of peripheral T cell subsets, especially of TcR1 positive cells, in contrast to the pronounced accumulation in the afflicted tissues.

Animals↗
PubMed1990

Analysis of the immune-encodrine feedback loop in the avian system and its alteration in chickens with spontaneous autoimmune thyroiditis.

In both mammals and chickens, immunization with exogenous antigens results in a surge of serum glucocorticoid hormone levels concomitant with the antibody response. This effect is mediated by glucocorticoid-increasing factors (GIF) produced by cells of the immune system. In the avian system, GIF appear to act via the hypothalamo-pituitary axis and not directly on the adrenal gland. Interleukin 1 is the main active substance responsible for GIF activity, as shown by molecular sieve and immunoaffinity chromatography studies. In contrast to data from mammals, we found no evidence that interleukin 2 elevates chicken corticosterone. Obese strain chickens with spontaneous Hashimoto-like autoimmune thyroiditis are deficient in their in vivo GIF response. Because no differences were found between autoimmune and healthy chickens in the corticosterone response of the adrenal gland after ACTH administration, and since autoimmune animals are able to react normally to immobilization stress, it is assumed that this deficiency is due to a specific defect rather than a general disturbance in the endocrine system.

Adrenal Glands↗
PubMed1989

Typing of MHC haplotypes in OS chicken by means of RFLP analysis.

For the analysis of the genetic background of autoimmune thyroiditis we used the Obese strain (OS) chicken model which develops a SAT. Practically all animals from this strain show severe lymphoid infiltration of the thyroid gland and circulating autoantibodies against thyroglobulin (Tg-AAb) within a few weeks after hatching. Of the 3 MHC haplotypes (B5, B13, B15) present in the OS, B13 was mostly associated with severe thyroid infiltration. Haplotypes B5 and B15 were associated both with severe, as well as with mild infiltration. To clarify these controversial results published by different groups and to further assess the role of the MHC in the development of SAT, we selected by appropriate breeding sublines with high and low levels of Tg-AAb. With the help of serological methods and GvH assays we were not able to find additional differences in the MHC antigens of that line. Therefore, for further characterization of these haplotypes, RFLP analysis was applied in the present study. Southern blots were done with restriction enzyme digests of erythrocyte DNA hybridized with a chicken cDNA probe (code-p234) for MHC class II antigens. The Southern blots with BamH-I digests showed at least 5 bands, four of which were polymorphic. Four RFLP patterns emerged, two of which were observed within chickens with the B15 haplotype. The confirmation of this RFLP heterogeneity within serologically identical haplotypes requires additional analysis.

Animals↗
PubMed1987

Relationship between the expression of class I antigen and reactivity of chicken thymocytes.

The expression of major histocompatibility complex (MHC) class I antigens in ontogenesis and the distribution of B-F+ cells, defined by means of a monoclonal antibody, were studied by indirect membrane immunofluorescence tests on suspensions of thymus, bursa, spleen, peripheral blood lymphocytes (PBL) and red blood cells (RBC) from 18-day-old chicken embryos and chickens from 1-90 days after hatching. At 18 days of incubation and at the first day after hatching, RBC, PBL, and the cells from bursa and thymus are negative. The percentage of positive PBL and bursal cells increases up to 9 days after hatching. By 2 weeks after hatching almost 100% of the RBC, PBL, bursa, and spleen cells were positive whereas the thymus showed only 20% positive cells. Analysis on 4-micron-thick, frozen acetone-fixed tissue sections of thymus showed that medullary cells are positive, while the cortical area is negative. The graft-versus-host (GvH) competence of these thymus subpopulations was compared after sorting by the fluorescence-activated cell sorter and injection into MHC incompatible embryos. GvH reactivity was associated primarily with the B-F+ population. Double staining studies with peanut agglutinin (PNA)-fluorescein isothiocyanate and a rabbit-anti-Ig tetramethyl isothiocyanate-conjugate proved that the PNA- thymocytes are identical with B-F+ thymocytes.

Age Factors↗
PubMedDate not supplied

APP peptides stimulate lymphocyte proliferation in normals, but not in patients with Alzheimer's disease.

We hypothesized that metabolic products of the Alzheimer beta amyloid precursor protein (APP) might be targets for cells of the immune system. To test this hypothesis, peripheral blood lymphocytes from young and old healthy blood donors and patients with Alzheimer's disease were analysed for their responsiveness upon stimulation with amyloid beta protein as well as with four other synthetic peptides corresponding to parts of the APP sequence. Stimulation of resting blood lymphocytes from young and old healthy blood donors resulted in IL-2 receptor expression and proliferation in both age groups. In contrast, lymphocytes from the majority of patients with Alzheimer's disease did not proliferate, when stimulated with APP peptides, while their proliferative response to anti-CD3 was unimpaired. This lack of proliferative responsiveness to APP peptides was not due to apoptosis, but could reflect T cell anergy, as it was accompanied by unimpaired IL-2 receptor expression. The results suggest that autoreactive lymphocytes with specificity for metabolic products of APP occur in healthy individuals. These cells may be of relevance for the elimination of potentially amyloidogenic substances. This mechanism could be impaired in patients with Alzheimer's disease.

Adolescent↗