Search PubMed⌕ Search

Biomedical subjects

K Schauenstein

Publications and source records attributed to K Schauenstein.

At least 109 records · Page 6Linked to original sources
PubMed1986

Thymus involution induced by 5-azacytidine.

Hypomethylation of DNA, which can be achieved by incorporation of 5-azacytidine, has been correlated with derepression of genes. In order to examine the in vivo effects of 5-azacytidine on organ development and differentiation, young rats were treated with the drug. There was an almost complete reduction of thymus and a marked reduction of spleen weight, while other organs, including testes were only marginally affected. Control experiments with cytosine-arabinoside suggest that treatment with an inhibitor of DNA replication per se is not responsible for the very rapid thymus involution triggered by 5-azacytidine in rats. In spite of the drastic reduction of thymus and spleen weight, lymphocytes of these organs were not impaired in their response to the T cell mitogen Concanavalin A.

Animals↗
PubMed1985

Photometric analysis of antifading reagents for immunofluorescence with laser and conventional illumination sources.

Bleaching of stained objects is a major problem in immunofluorescence. The prevention of fluorescence fading would allow longer observation times, photographic documentation, fluorometry, and pattern recognition. Fluorescein kinetics and fluorescence intensities (FI) of fluorescein isothiocyanate (FITC) conjugate-stained Sephadex beads were studied with previously described "antibleaching" reagents using an argon laser as the excitation light source. Eight antibleaching reagents were tested (sodium azide (NaN3), sodium iodide (NaI), polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), 1,4-di-azobicyclo-(2,2,2)-octane (DABCO), p-phenylenediamine (PPD), n-propylgallate, and sodium dithionite (Na2S2O4]. Sodium azide and sodium iodide were found to increase FI. This was likewise found with mercury arc illumination and hence they may prove useful for routine immunofluorescence tests. PPD was found to accumulate on the surface of the beads and to disturb immunofluorescence by autofluorescence. The value of any of the other reagents in immunofluorescence is questionable.

Argon↗
PubMed1985

In vitro T cell hyperreactivity in Obese strain (OS) chickens is due to a defect in nonspecific suppressor mechanism(s).

Spontaneous autoimmune thyroiditis of OS chickens is associated with a marked hyperreactivity of the T cell system. The purpose of the present study was to investigate the underlying regulatory mechanisms. Co-cultivation experiments between Con A-stimulated OS and NWL lymphocytes in communicating cultures revealed soluble regulatory factors to be responsible for the observed functional differences: the high proliferative response to Con A and hyperproduction of IL 2 of OS cells was found to be due to a deficiency in the conditioned medium of dialyzable inhibitory factor(s) that regulate IL 2 secretion of NWL lymphocytes. Furthermore, sera of young NWL chickens were found to profoundly inhibit the IL 2-promoted lymphoblast proliferation. This IL 2 antagonizing activity is lost with age (3 to 6 yr) and was found to be significantly diminished in OS birds throughout ontogeny, thus pointing to possible parallels between immune regulatory dysfunction in autoimmunity and in physiologic aging. Both enhanced T cell response and the defect in serum suppressor were inherited by (OS X CB)F1 animals, indicating that these two aberrations may be related to each other.

Animals↗
PubMed1985

Analysis of lymphocytes infiltrating the thyroid gland of Obese strain chickens.

Lymphocytes were isolated from the infiltrated thyroid glands of 2- to 5-wk-old Obese strain (OS) chickens with spontaneous autoimmune thyroiditis (SAT). Immunofluorescence analysis performed by using a panel of monoclonal and polyclonal antibodies revealed that 60% of thyroid infiltrating leukocytes (TIL) were mature T cells, a large portion of which seemed to be in an activated state bearing Ia-like antigens (10%) as well as a surface determinant associated with T cell activation (16%), i.e., possibly the receptor for interleukin 2 (IL 2). Furthermore, a relatively high plasma cell content (5%) was observed. TIL exhibited high proliferative responses to T cell mitogens (concanavalin A, phytohemagglutinin) and IL 2, but only weak responses to the B cell mitogen LPS from Salmonella typhimurium. When injected into newly hatched, MHC-identical, irradiated normal chickens, TIL induced both the production of autoantibodies and thyroid infiltration. Peripheral lymphocytes from spleen and blood and thymocytes from the same OS donors had no effect. Analysis of chemically (cyclophosphamide) bursectomized OS chickens suggested that an intact B cell system was not obligatory for the induction of SAT. TIL from these chickens consisted of 77% T cells and less than 1% B lymphocytes, yet were capable of inducing severe thyroid infiltration upon transfer into normal recipients. These findings emphasize the importance of the T cell system in the initiation of SAT.

Animals↗
PubMed1985

Enhanced response to Con A and production of TCGF by lymphocytes of obese strain (OS) chickens with spontaneous autoimmune thyroiditis.

The mitogenic response to Con A and the production of T cell growth factor or interleukin 2 (IL 2) by splenic and peripheral blood lymphocytes of obese strain (OS) chickens with spontaneous autoimmune thyroiditis have been investigated. By using an optimized method with Con A-coated chicken erythrocytes (MRC), lymphocytes of OS chickens were found to exhibit significantly elevated mitogenic responses as compared with cells from either Normal White Leghorn chickens (NWL) or animals of the Cornell C-Strain (CS), from which the OS has originally been developed. This difference was observed throughout ontogeny up to 15 mo of age, and was associated with increased levels of IL 2 activity in the culture supernatants. The elevated responsiveness of OS T lymphocytes was also found to be manifested in the expression of receptors for IL 2, because Con A-stimulated lymphocytes of OS birds were significantly more effective than those from normal controls in absorbing IL 2 activity from conditioned media (CM) of stimulated spleen cells. High concentrations of CM were suppressive in IL 2 assays, signaling the presence of an inhibitory factor(s) in addition to IL 2. An additional indication for defective immunoregulation was that CM from OS lymphocyte cultures showed significantly less of this suppressive activity in comparison with CM of normal (NWL and CS) lymphocyte cultures. Finally, the spontaneous uptake of 125IUdR of embryonic and early post hatching OS spleen lymphocytes was consistently and significantly enhanced. This difference, however, in contrast to the one observed in Con A responses, was found to decrease with age. The data are discussed in view of the contradictory results concerning T cell functions reported for several autoimmune states in mammals.

Aging↗
PubMed1984

Avian lymphokines: an improved method for chicken IL-2 production and assay. A Con A-erythrocyte complex induces higher T cell proliferation and IL-2 production than does free mitogen.

Optimized production conditions and a functional assay of avian T cell growth factor (TCGF) or interleukin 2 (IL-2) are described. Treatment of lymphocytes with mitogen (Con A)-coated chicken red blood cells (MRC) resulted in markedly enhanced mitogenic response and IL-2 secretion compared to stimulation with free Con A. A positive correlation (r = 0.89) was found between mitogenic response and IL-2 activity of conditioned media. Enrichment of target cells, i.e., Con A lymphoblasts, by Percoll consistently improved the sensitivity of the IL-2 assay. The half-life time of chicken IL-2 at 40 degrees C was 9.7 +/- 1.7 h, which was considerably shorter than the value obtained for murine IL-2, i.e., 53.1 +/- 8.5 h. High concentrations of conditioned media were found to contain a dialysable factor that suppressed IL-2 promoted blast proliferation. The relevance of the data for in vitro analysis of T cell function as well as for establishing T cell lines in the chicken system are discussed.

Animals↗
PubMed1984

Structure- and configuration-dependent effects of C18 unsaturated fatty acids on the chicken and sheep erythrocyte membrane.

High concentrations of unsaturated fatty acids are known to cause hemolysis. At low concentrations, however, unsaturated cis fatty acids have been found to protect erythrocytes against hypotonic hemolysis. In the present experiments we examined the effect of oleic (18:1), linoleic (18:2), linolenic (18:3), and elaidic (18:1) acid on the osmotic fragility of chicken and sheep erythrocytes, which markedly differ in their resistance to osmotic rupture. The results are summarized as follows: (A) The phenomenon of stabilization was observed in both species alike. (B) Interaction of cells with the fatty acids under isotonic conditions led to a persistent stabilization, i.e., the cells remained more resistant against osmolysis even after several washings. (C) Oleic and elaidic acid protected against osmotic rupture with a high degree of specificity. Linoleic and linolenic acid were much less protective. Thus, this effect appears to be specific for one double bond. (D) Contrary to the unsaturated fatty acids with cis configuration, elaidic acid with the trans configuration showed no biphasic behaviour, and even at the highest concentrations applied no hemolysis was observed.

Animals↗
PubMed1984

Distribution and functional analysis of B-L/Ia-positive cells in the chicken: expression of B-L/Ia antigens on thyroid epithelial cells in spontaneous autoimmune thyroiditis.

The B-L region of the chicken major histocompatibility complex (MHC), the so-called B-locus, corresponds to the murine H-2 I-region. Using alloantibodies and monoclonal antibodies to B-L we analyzed: (a) the tissue distribution of B-L+ cells, (b) the function of B-L+ cells, and (c) the possible role of B-L+ cells in the development of spontaneous autoimmune thyroiditis (SAT) in Obese strain (OS) chickens. The tissue distribution of B-L+ cells in peripheral blood and various lymphoid and nonlymphoid organs corresponds to what is known for mammals. In the bursa of Fabricius most lymphoid cells and the dendritic cells carry the B-L antigen; B-L+ thymic nurse cells (TNC) first appear on day 17 of embryonic life; chickens possess dendritic B-L+ cells in the skin resembling mammalian Langerhans cells; in addition we found that the microglia is unequivocally B-L+. B-L+ peripheral blood lymphocytes (PBL) were separated with a fluorescence-activated cell sorter. Ten percent of unstimulated PBL and 60% of phytohemagglutinin (PHA) stimulated T-cell blasts are B-L+. In graft-vs-host (GvH) assays B-L- cells were identified as the effector cells. These cells respond to PHA and concanavalin A (Con A), but not to pokeweed mitogen (PWM). B-L+ cells cannot be stimulated by Con A and PHA, but respond to PWM. They possess only a very low activity in GvH assays which can be inhibited by anti-T-cell sera. In OS chickens B-L+/non-B/, non-T and B-L+ T (blasts?) cells are found in the "first line" of mononuclear cell infiltration in the thyroid glands. Most interesting, thyroid epithelial cells--which are normally B-L- -become B-L+ in the neighbourhood of B-L+ infiltrating mononuclear cells. This observation may be of significance for autoantigen presentation and perpetuation in autoimmune thyroiditis. Finally, OS thymuses contain significantly less TNC than normal controls.

Animals↗
PubMed1984

Exocytotic exposure and retrieval of membrane antigens of chromaffin granules: quantitative evaluation of immunofluorescence on the surface of chromaffin cells.

The exocytotic exposure of antigens of chromaffin granule membranes was studied with chromaffin cells isolated from bovine adrenal medulla. Antigens on the cell surface were visualized by indirect membrane immunofluorescence employing antisera against glycoprotein III and dopamine beta-hydroxylase. With unstimulated cells, only weak immunofluorescence on the cell surface was observed, whereas stimulated cells (with carbachol or Ba2+) exhibited much stronger reactions. In all cases the staining appeared as dots and patches. To quantitatively prove these observations, we analyzed the immunostained cells using a fluorescence-activated cell sorter. After stimulation, the average fluorescence intensity of the cell population was enhanced. This increase correlated with the degree of catecholamine secretion. The fluorescence intensity of stimulated cells varied over a broad range indicating that individual cells reacted variably to the secretagogues. When stimulated cells were incubated at 37 degrees C for up to 45 min after stimulation, a decrease of membrane immunofluorescence approaching that of unstimulated control cells was observed. Apparently, the membranes of chromaffin granules, which had been incorporated into the plasma membrane, were retrieved by a specific and relatively fast process. This retrieval of the antigen from the cell surface was blocked by sodium azide, but not influenced by colchicine, cytochalasin B, and trifluoperazine. The quantitative methods established in this paper should prove useful for further study of the kinetics of the exo-endocytotic cycle in secretory tissues.

Adrenal Medulla↗
PubMed1983

Characterization of chicken lymphocyte subsets separated by peanut agglutinin.

The reactivity of chicken lymphocytes isolated from bursa, thymus, spleen, and peripheral blood (PBL) with peanut agglutinin (PNA) has been investigated. High numbers of cells binding PNA (PNA+ cells) were found in bursa (74.5%) and thymus (85.2%), as well as in the peripheral organs (spleen and PBL, 43.8 and 70%, respectively). In the latter organs, the levels of PNA+ cells exceeded by far the values reported for mammals. Separation of PNA+ and PNA- cells from different organs was achieved by selective agglutination with the lectin or by affinity chromatography on immobilized PNA. Experiments combining the use of limiting concentrations of neuraminidase to cleave off sialic acid from the surface membrane of splenocytes that do not bind PNA (PNA- cells), followed by agglutination with the lectin, suggested that the high binding of PNA to mature lymphocytes is most likely due to a low degree of sialylation of chicken cell surface glycoconjugates. The functional properties in vitro of PNA+ and PNA- spleen cell fractions were assayed in mitogen responses (PHA, Con A, PWM), the mixed-lymphocyte reaction (MLR), and the in vitro anti-SRBC antibody response. In all three systems the responses of the PNA+ fraction were found to be significantly higher than those of the PNA- cells. Mixing experiments revealed that irradiated (1500 R) PNA- cells preferably suppress pure T-cell responses of unfractionated spleen cells, whereas PNA- cells exerted a stronger suppressive effect on responses involving B cells. Thus, in the chicken, PNA may be a valuable tool to distinguish subsets of suppressor cells with different target specificity.

Animals↗
PubMed1982

IgG-Fc and C3 receptors in the chicken: distribution, tissue localization and functional significance.

This paper summarizes data obtained in our laboratory on the demonstration of receptors for IgG-Fc (FcR) and complement (CR) on mononuclear cells of the fowl. A clearcut distinction of these two structures on spleen cells was achieved in rosette assays using SRBC coated with rabbit IgG as indicator cells which bind avian complement, but are not bound by the FcR. The tissue distribution and localization of FcR and CR positive cells was studied in mixed hemadsorption assays on sections of both central (bursa, thymus) and peripheral (spleen) lymphoid organs from normal chickens, as well as lymphocytic infiltrated thyroid glands from animals of the Obese strain (OS) afflicted with spontaneous autoimmune thyroiditis. The possible significance of both receptors in the pathogenesis of this autoimmune process is discussed.

Animals↗
PubMed1982

Avian lymphokines: 1. Thymic cell growth factor in supernatants of mitogen stimulated chicken spleen cells.

The present study provides first evidence for the presence of a thymic cell growth factor (TCGF) in supernatants (20 hrs) of mitogen (Con A) stimulated chicken spleen cells. 2 out of 3 batches of supernatant prepared according to a procedure originally described for the mouse system (10) induced a vigorous proliferative response of Con A prestimulated chicken spleen cells without significant mitogenic effect on unstimulated lymphocytes. No crossreactivity of this chicken-TCGF was observed with prestimulated murine lymphocytes, nor did potent mouse-TCGF preparations exhibit any proliferative effect on chicken cells. The implications of these data for both phylogenetic as well as practical experimental aspects are discussed.

Animals↗
PubMed1982

Tissue localization of lymphocyte surface antigens and receptors for immunoglobulin G Fc and complement in the chicken.

Frozen sections of chicken lymphoid organs were examined for lymphocyte surface antigens by antisera to T and B lymphocytes (ATS;ABS), and for the presence of immunoglobulin (Ig) G Fc and complement receptors (FcR;CR) by hemadsorption with sheep erythrocytes (E) coated with chicken IgG(EA), and E coated with rabbit IgG and chicken complement (EAC). In the spleen FcR positive cells were confined to the periellipsoidal sheaths and the germinal centers. CR positive cells were found in the same spleen areas, as well as in the medulla of bursal follicles. These lymphoid areas reacted strongly with ABS, but they also stained with neutral alpha-naphthyl butyrate esterase, and phagocytosed carbon particles were found in the periellipsoidal sheaths. Furthermore, in vivo treatment with cyclophosphamide, which resulted in pronounced B-lymphocyte depletion, did not affect FcR activity, but reduced CR activity significantly. These data indicate that the FcR activity demonstrated in tissue sections is mainly confined to mononuclear phagocytes, while the CR positive cells are mainly B lymphocytes.

Animals↗
PubMed1981

Localization of IgGFc and complement receptors in chicken lymphoid tissue.

Chicken lymphoid organs were examined for IgGFc and complement receptors (FcR/CR) by immune adherence on frozen tissue sections. Indicator systems were sheep erythrocytes (E) coated with chicken anti-E IgG (EAch), E coated with rabbit anti-E IgG (EArab) and normal chicken serum (EAC), and FITC-labelled zymosan particles coated with chicken serum (ZyC). In the spleen, FcR and CR activity was confined to B-dependent areas, i.e. the periellipsoidal sheaths and germinal centres and the red pulp. No FcR were found in the thymic or bursal lymphoid tissue, but CR activity was observed in the medulla of bursal follicles. Chicken and turkey IgG, chicken IgGFc, and bovine serum albumin (BSA)--chicken anti-BSA complexes inhibited binding of Each. No inhibition was obtained with chicken IgGF(ab')2, IgM or albumin, or with BSA--rabbit anti-BSA complexes and human or rabbit IgG. E did not adhere to the sections, nor did EArab, EArab incubated with heat-inactivated chicken serum, or EAC complexes prepared with EArab and guinea-pig complement. The data suggest that chicken B lymphocytes and macrophages have receptors for avian IgGFc and C which can be demonstrated in tissue sections.

Animals↗
PubMed1980

[Immunological studies on conjunctivitis follicularis].

Conjunctivitis follicularis is characterized by the appearance of cellular infiltrates consisting of lymphocytes, eosinophils and mast cells; this has led to the assumption of an allergic etiology in many cases. In a first attempt to prove this hypothesis three cases of conjunctivitis follicularis were investigated using the following immunological methods: (1) determination of immunoglobulins in the lacrimal fluid by means of quantitative precipitation (IgG, IgA, IgM), and by a direct radioimmunoassay for IgE; (2) direct immunofluorescence test on cryostat sections of biopsy specimens of diseased conjunctiva to detect immunoglobulin-producing plasma cells. According to initial results the infiltrated conjunctiva contains considerable numbers of plasma cells producing mainly IgA, and IgM. Plasma cells positively stained with anti-IgG and notably with anti-IgE were only rarely found. These findings, which were also supported by the quantitative Ig determinations in the lacrimal fluids, tend to rule out an allergic, IgE-mediated pathomechanism in these cases.

Adult↗