Biomedical subjects

G Wick

Publications and source records attributed to G Wick.

At least 253 records · Page 14Linked to original sources

PubMed1986

Lymphocyte membrane lipid composition and mitogen responsiveness in chickens: role of membrane "fluidity".

After establishing optimal conditions for measuring the membrane lipid packing density ("fluidity") of chicken peripheral blood lymphocytes, the fluidity was modulated in vitro by incubation in cholesterol or phospholipid ("active lipid", AL)-enriched serum-free tissue culture medium. The effect of these lipids on mitogen responsiveness was then investigated, the aim being to determine whether the observed enhancement/suppression was membrane mediated, i.e. explainable by fluidity changes. Chicken peripheral blood lymphocytes exhibited no requirement for exogenous cholesterol; low concentrations did not affect the mitogen response while the higher concentrations, which induced a measurable decrease in membrane fluidity, were usually mildly suppressive. Pre-incubation did not increase this suppressive effect and we believe it not to be membrane mediated. AL, at low concentrations which induced no changes in membrane fluidity, prolonged the phytohemagglutinin response, enhancement being evident only after the peak; we interpret this as a nutrient effect. At the higher concentrations, which induced large increases in fluidity, a transient enhancement was followed by suppression; suppression was delayed in onset when AL was added 4 h after phytohemagglutinin stimulation. It is therefore an early event which may be mediated through changes in membrane fluidity.

Animals↗

PubMed1986

Thymic nurse cells: a school for alloreactive and autoreactive cortical thymocytes?

The possibilities for functional analysis of thymic nurse cells (TNC) have so far been hampered by the low yield of these cells by means of gradient centrifugation and their fragility preventing purification by a fluorescence-activated cell sorter. Furthermore, they are extremely unstable in cell culture. Here we present functional data obtained by the analysis of single TNC in an avian system: the chicken with its extramaternal embryonic development prompted us to use the chorioallantoic membrane (CAM) pock formation assay to investigate the possible graft-vs.-host reactivity (GVHR) of TNC lymphocytes (TNC-L). The CAM assay proved to be an optimal and unique "cell culture" system for the investigation of the functional characteristics of TNC. Our data show that TNC-L, unexpectedly, are able to exert a GVHR on allogeneic CAM with the very high efficiency of 1/13 as compared to thymocytes of the same donors showing a GVHR efficiency of 1/350. TNC-L are even able to induce GVH-like reactions in syngeneic combinations, while thymocytes and peripheral blood lymphocytes from the same donors always remain negative.

Allantois↗

PubMed1986

A monoclonal antibody reacting with a membrane determinant expressed on activated chicken T lymphocytes.

A monoclonal antibody (INN-CH-16) was prepared which reacts with a cell surface antigen termed chicken activated T lymphocyte antigen. This antigen is expressed on antigen- or mitogen-activated T lymphocytes and is not present on nonstimulated lymphocytes. It has an apparent molecular mass of 48-50 kDa under reducing conditions. The value of this antibody for the immunohistochemical characterization of infiltrating cells in the thyroid glands from Obese strain chickens with spontaneous thyroiditis is demonstrated.

Animals↗

PubMed1986

Sex steroid and glucocorticoid receptors in the bursa of Fabricius of obese strain chickens spontaneously developing autoimmune thyroiditis.

The female sex develops autoimmune disease far more often than the male. This is claimed to be due to differences in peripheral sex steroid levels. We have examined in the bursa of Fabricius of Obese strain (OS) chickens, which spontaneously develop autoimmune thyroiditis, as well as in their healthy counterparts androgen(AR)-, estrogen(ER)-, progestin(PR)- and glucocorticoid(GR)-receptors in an attempt to elucidate possible further pathomechanisms, namely at the target site of steroid hormones. The characterization (affinity, specificity, association- and dissociation-rate, sedimentation behaviour) of all four types of receptors revealed no difference between sex or strain. Furthermore, the ontogeny study of the receptor capacity and affinity from the 7th embryonic day (i.e. before lymphocyte settlement) until bursa involution, again showed no difference between OS and healthy chickens of either sex. Thus, it can be concluded that the principal sex dependency of the susceptibility to autoimmune disease results predominantly from differences in sex steroid levels per se, although alterations in mechanisms beyond the cytosolic receptor level can presently not be excluded.

Animals↗

PubMed1986

Class II antigens in Hashimoto thyroiditis. I. Synthesis and expression of HLA-DR and HLA-DQ by thyroid epithelial cells.

Aberrant expression of HLA-DR antigens on epithelial cells is seen in various organ-specific autoimmune disorders including Hashimoto thyroiditis (HT). Expression of HLA-DQ has so far not been demonstrated on these cells. We report here that thyroid epithelial cells (TEC) in HT, in addition to the known aberrant expression of HLA-DR, coexpress HLA-DQ antigens. Furthermore we provide evidence that class II antigens are synthesized by TEC themselves by demonstration of intracellular HLA-DR gamma-chain. These findings support the theory that TEC may be able to present (auto)antigens in vivo thus perhaps contributing to the perpetuation of thyroid destruction. As expression of class II antigens on TEC was never observed in non- or weakly infiltrated areas, we propose that infiltration by T cells is necessary to induce this aberrant expression of class II antigens.

Epithelium↗

PubMed1986

Class II antigens in Hashimoto thyroiditis. II. Expression of HLA-DR on infiltrating mononuclear cells in peripolesis.

Surgical specimens from patients with Hashimoto thyroiditis (HT) or colloid goiter (CG) were analyzed using an immunofluorescence double staining technique to characterize the infiltrating mononuclear cells (MNC) and to determine the possible expression of HLA-DR antigens by these cells. In HT the majority of infiltrating MNC were T cells. In the interstitium T cells with helper/inducer phenotype (Leu 3a+) were more abundant than those with suppressor/cytotoxic phenotype (OKT8+) and approximately 10-25% of all T cells expressed HLA-DR. Among the cells in peripolesis [i.e., protruding between thyroid epithelial cells (TEC)] OKT8+ cells were observed more frequently than Leu 3a+ cells, expression of DR antigens being 7 and 12%, respectively. The occurrence of Leu 3a+ cells in peripolesis is in marked contrast to the findings in colloid goiter where the intraepithelial population of MNC is almost exclusively composed of OKT8+ cells. The various ways in which the peripoletic Leu 3a+ cells could contribute to the special pathogenesis of HT are discussed.

Antibodies, Monoclonal↗

PubMed1986

The role of genetically-determined primary alterations of the target organ in the development of spontaneous autoimmune thyroiditis in obese strain (OS) chickens.

Immunologists working in the field of autoimmunity tend to concentrate all their efforts on the elucidation of possible malfunctions of the immune system, particularly pathologic changes of immune regulation. Also in the OS model various groups of investigators emphasized this approach, although it was already clear early in the history of this model that SAT has a multigenic background. The fact that this disease cannot be transferred into normal, histocompatible animals without an appropriate non-MHC linked genetic background was a strong indication that detailed studies of thyroid-associated factors may be warranted for the elucidation of the pathogenesis of this disease and perhaps also its human counterpart, Hashimoto thyroiditis. Since several reviews on the immunologic aspects in the OS model have been published in recent years we have in this communication attempted to discuss the - mostly still rudimentary - findings concerning the target organ itself, including morphological changes before the beginning of infiltration, the analysis of Tg, the altered thyroid function before onset of SAT, the results of cross-breeding studies of OS and inbred normal chickens in respect to the susceptibility of the offspring for the transfer of SAT, the possible role of a virus infection and the aberrant expression of MHC class II antigens on TEC. Cross-breeding studies revealed that most probably a single gene is responsible for the primary altered thyroid function and at least 3 genes code for the susceptibility of the OS thyroid gland to the autoimmune attack. It is not yet clear for which of the above-mentioned observations each of these genes is responsible and what is/are the initial triggering mechanism(s). Ongoing studies in our laboratory concentrate on this question, specifically the potential role of endogenous viruses in this process.

Animals↗

PubMed1986

Genetic background of spontaneous autoimmune thyroiditis in the obese strain of chickens studied in hybrids with an inbred line.

To determine the number and function of genes which are responsible for spontaneous autoimmune thyroiditis (SAT) in the obese strain (OS) of chickens we crossed birds of this strain (B15/B15) with those of the inbred CB line (B12/B12). The progeny was analyzed for autoantibodies to thyroglobulin (TgAAb) and for histopathological changes in the thyroid glands. In F1 (OS X CB) hybrids only those animals which derived from CB mothers had circulating TgAAb, the progeny from the reverse combination female OS X male CB was negative. Since the disease is not inherited by OS males only, we conclude that maternal TgAAb, which are transferred from the egg yolk to the embryo, might prevent the immune system of the F1 chickens from TgAAb formation via blocking or eliminating the respective antigens. Those F1 hybrids which have high TgAAb levels in the serum show only little or no thyroiditis. Together with other observations, these data lead to the conclusion that the thyroid gland of the F1 hybrids is not susceptible to TgAAb. This supports previous findings that a genetically determined thyroid abnormality is a prerequisite for the full development of SAT. The low degree of SAT in backcross (F1 X OS) animals and F2 hybrids suggests that several genes are involved in the disease. MHC typing of these generations revealed that the B haplotype affects the time of SAT onset.

Animals↗

PubMed1986

Identification of binding site for heparin and other polysulfated glycosaminoglycans on human thrombocytes.

Heparin and other polysulfated glycosaminoglycans (GAGPS) can evoke an immune response when complexed to the surface of platelets in vivo. We have previously reported on the detection and characteristics of such antibodies leading to thrombocytopenia. Here we report data concerning the biochemical characterization of the heparin-/GAGPS-binding site on human thrombocytes. By means of heparin affinity chromatography, GAGPS chromatography and subsequent 'Western blotting' of specifically eluted proteins we were able to detect two proteins of apparent molecular mass of 207 and 170 kilodaltons, which could be reduced to 57 and 142 kilodaltons, respectively. The 170-kilodalton glycoprotein was stained by the carbohydrate specific PAS-reagent and by surface labeling with 3H. The second molecule binding to heparin (GAGPS)-Sepharose was detected by platelet surface labeling with 125I, protein-specific staining Coomassie brilliant blue and PAS staining. Binding studies using enzyme-labeling techniques with five monoclonal antibodies (MCA) against platelet surface proteins GPI, GPIIb/IIIa complex, GPIIIa and CRI (C3b receptor) revealed specific interaction of the 170-kilodalton heparin-binding glycoprotein with an MCA to GPI, suggesting identity or immunological cross-reactivity of these two moieties. No specific reactions were observed between the 207-kilodalton glycoprotein and any of the MCA tested. For further evaluation of the antigenicity of separated platelet proteins, an ELISA in microtiter plates was developed, and a cellular sandwich ELISA for serological detection of antibodies against whole native thrombocytes or GAGPS-derivatized proteins was set up.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗

PubMed1986

Simple method for comparing large numbers of flow cytometry histograms exemplified by analysis of the CD4 (T4) antigen and LDL receptor on human peripheral blood lymphocytes.

We have developed a simple method for comparing the relative fluorescence intensity (FI) of flow cytometry histograms. It entails assessment of the FI (equivalent to the fluorescence-activated cell sorter (FACS) channel) of the 50th or 75th percentiles of either positively stained cells or the total cell population. We illustrate the method with dilution curves of 1) monoclonal antibodies against the T4 surface antigen of human peripheral blood lymphocytes and 2) fluorescent low density lipoprotein (LDL) binding to the human peripheral blood lymphocytes LDL receptor. We demonstrate the versatility of the method by characterizing the binding properties of fluorescent LDL to their receptors. Binding was shown to be specific and of high affinity, and to reach a steady state plateau at about 2 hr; the affinity of fluorescent LDL for the receptor was found to be two to three times higher than that of the unlabeled LDL.

Antibodies, Monoclonal↗

PubMed1986

The antigenic surface of human chorionic gonadotropin as mapped by murine monoclonal antibodies.

We present a map describing the antigenic determinants (epitopes) of the human CG (hCG) molecule. A panel of monoclonal antibodies to hCG, previously characterized by us was incorporated into two-site binding assays to probe hCG by a 21 X 11 matrix of 231 pairs of MCA. Nine different reaction patterns of reciprocal homology were distinguished and interpreted as representing nine separate and distinct epitopes. Three of them localize on the alpha-subunit, 4 on the beta-subunit and 2 were expressed by the intact hCG (holo-hCG) molecule only, hence designated conformational (c) epitopes. Epitope-contingency analysis revealed that each of the 2 subunits of hCG possesses 1 epitope that is neither adjacent to nor overlapping with any of the other 8 epitopes. The latter were arranged in a complex cluster from which the c-epitopes protrude. Whereas the alpha- and c-epitopes are specific for glycoprotein hormones of human origin and for hCG, respectively, the beta-epitopes appeared to be evolutionarily highly conserved structures: with 1 exception, they were also present on the beta-chain of LH from many different mammalian species.

Animals↗

PubMed1986

Congenital hypothyroidism in a Turkish family: the role of immunoglobulins blocking the trophic effects of TSH and maternal-foetal relationship.

A Turkish family with frequent intermarriages is described, in which two siblings were born with persistent forms of congenital hypothyroidism, in the elder child concomitant with absent radioactive thyroid imaging. The mother was clinically euthyroid throughout the period of observation, but showed in addition to thyroid microsomal antibodies, high levels of immunoglobulins blocking the trophic action of TSH. These maternal growth blocking antibodies were transiently present in the youngest of the siblings (from birth to 2 months of age). She had a relatively mild form of congenital hypothyroidism (T3: 33 micrograms/100 ml; T4: 3.9 micrograms/100 ml). The older sibling, with proven non-functioning thyroid tissue (negative thyroidscan, T4: 0.4 microgram/100 ml) produced the growth-blocking immunoglobulins herself and may thus represent a juvenile form of thyroid autoimmunity with a very early onset. An aunt and uncle of the children, both hypothyroid since birth, were at the age of 19 and 18 years weakly positive for growth blocking immunoglobulins. This study indicates that familial forms of congenital hypothyroidism are probably complex and may be brought about by maternal to foetal passage of thyroid reactive autoantibodies, but also by the inheritance of a trait for thyroid autoimmunity. In some cases these two mechanisms might act in conjunction.

Adolescent↗

PubMed1986

Globular domain of basement membrane collagen induces autoimmune pulmonary lesions in mice resembling human Goodpasture disease.

A distinct circulating antibody response could be evoked in C57BL mice after immunization with the globular domain NC1 of basement membrane collagen IV obtained from the mouse Engelbreth-Holm-Swarm tumor when injected together with complete Freund's adjuvant. The antibodies reacted with various subunits of NC1, did not cross-react with other basement membrane proteins, and exhibited a tissue reactivity restricted to certain basement membranes. Tissue-bound antibodies could be detected by direct immunofluorescence and were distributed together with C3 in a linear pattern along glomerular and alveolar basement membranes. Pathological changes were mainly observed in lung and kidney and consisted of inflammatory infiltrates and massive hemorrhages with strong granulomatous fibrotic development in the lung. Kidney alterations were comparably weaker and of focal nature. A nephrotoxic serum model showed rapid binding of rabbit antibodies against mouse NC1 to lung, liver, and kidney basement membranes which was followed several weeks later by an autologous phase with anti-rabbit IgG antibodies bound to basement membranes as immune complexes. There was no fibrotic response but hemorrhagic and inflammatory lung and kidney changes similar to those after active immunization were observed after passive transfer. The experimental NC1 autoimmune model has several features such as anti-NC1 response, tissue restriction, lung hemorrhages, and glomerulonephritis in common with patients suffering from Goodpasture disease. The development of lung fibrosis appears to be unique for the animal model.

Animals↗

PubMed1985

[The self and its enemy].

This essay uses the form of an imaginary debate between an immunologist and a non-immunologist to discuss the problem of immunological self-recognition and the clinical relevance of this phenomenon to the development of autoimmune disease. The first part deals with the communication between different cell types involved in normal and abnormal immune reactions. Then the problems of "physiological" autoimmunity and regulation of the normal immune response are discussed. The development of autoimmune diseases is reviewed on the basis of data obtained in the so-called Obese strain (OS) of chickens, which show a spontaneous hereditary autoimmune thyroiditis analogous to human Hashimoto thyroiditis. The role played by the thymus for the homeostasis of a normal immunological reactivity is emphasized. Finally, parallels are drawn between those mechanisms underlying the development of autoimmune disease and changes in the normal immune system with increasing age. The contribution finishes with some thoughts on the potential applications of our present knowledge of the process of auto-immunity to new therapeutic approaches to this large group of human diseases.

Aging↗

PubMed1985

Immunochemical and autoantigenic properties of the globular domain of basement membrane collagen (type IV).

Polyclonal rabbit antibodies raised against the globular domain NC1 of collagen IV from human placenta and a mouse tumor react with conformational antigenic determinants present on the NC1 hexamers and also with the three major subunits obtained after dissociation. The antibodies recognized unique structures within basement membranes and showed a broad tissue reactivity but only limited species cross-reactivity. Using these antibodies, it was possible to detect small amounts of collagen IV antigens from cell cultures and in serum. Monoclonal rat antibodies against mouse NC1 revealed a similar reaction potential. Autoantibodies could be produced in mice against mouse NC1 which react with kidney and lung basement membranes in a pathological manner, mimicking Goodpasture syndrome.

Animals↗

PubMed1985

Age-related changes in lymphocyte subset proportions, surface differentiation antigen density and plasma membrane fluidity: application of the eurage senieur protocol admission criteria.

Peripheral blood lymphocytes from 260 "apparently healthy" males and females, aged 20-97, have been investigated for age-related changes in a number of immunological parameters (percent and number of lymphocytes, OKT 4+ and OKT 8+ cells; OKT 4/8 ratio; intensity of fluorescence of OKT 4 and OKT 8 stained cells; membrane fluidity). Data were then reassessed after exclusion of people who did not conform to the SENIEUR PROTOCOL admission criteria of EURAGE (European Economic Community's Concerted Action Program on Aging) in order to investigate whether the differences observed were attributable to underlying disease. A slight decrease in the number and percentage of lymphocytes, OKT 4+ and especially OKT 8+ cells was found. Intensity of fluorescence of OKT 4 and OKT 8 stained cells from the elderly was reduced and may explain the lower percentages. Membrane fluidity was decreased in old persons (over the age of 75); the free cholesterol/phospholipid molar ratio in the serum increased up to the age of 75 and then declined, and it did not correlate with decreased membrane fluidity. Exclusion of the 20-60% of the study groups who were not eligible for admission according to the SENIEUR PROTOCOL criteria did not affect these results. The feasability and applicability of the PROTOCOL is discussed.

Adult↗

PubMed1985

Spontaneous autoimmune thyroiditis in obese strain chickens: a genetic analysis of target organ abnormalities.

In this study we investigated the genetic background of primary abnormalities found in the thyroid gland of Obese strain (OS) chickens with spontaneous autoimmune thyroiditis (SAT), i.e., susceptibility to passively transferred antibodies to thyroglobulin (TgAb) and incomplete suppression of iodine uptake by thyroxine (T4). Several crosses between the B15/B15 subline of OS chickens and the inbred CB line (B12/B12) were done and the progeny was analyzed for thyroiditis after injection of OS serum containing high titers of TgAb. It was found that passive transfer of TgAb increased the lymphoid infiltration in the thyroids of OS chickens, but had no effect on CB birds. A genetic analysis of backcrosses revealed that this trait is, in the case of simple Mendelian inheritance, encoded by at least three recessive genes. The thyroidal 131I uptake of these crosses under T4 was also determined and we found that this trait is most probably encoded by only one recessive gene.

Animals↗

PubMed1985

Structure and biology of the globular domain of basement membrane type IV collagen.

A procedure was developed for purifying the globular domain NC1 of basement membrane collagen from collagenase digests of a variety of tissues. The globule (Mr = 170,000) is a hexameric structure originating from two collagen IV molecules that are cross-linked at their COOH-terminal ends. Dissociation into subunits derived from alpha 1(IV) and alpha 2(IV) chains occurs at a pH below 4 and after denaturation (8 M urea). The subunits obtained include monomers (Mr = 28,000) and two different dimers (Da,Db) which are connected by disulfide bonds (Db) and/or nonreducible bonds (Da). Almost perfect reconstitution to hexamers is obtained in neutral buffer with mixtures of the subunits or purified dimers but not with purified monomers. Stabilization by dimer formation and other physical data suggest conformationally distinct segments within the subunits, which is also supported by a repeating subdomain structure deduced from cDNA sequences. Monocline crystals of NC1 give a sufficiently detailed X-ray diffraction pattern that should permit elucidation of the three-dimensional structure of the hexamer. Antibodies raised against the globular domain react with all subunits and mainly recognize epitopes stabilized by internal disulfide bridges and/or the hexameric assembly. Immunoprecipitation tests with these antibodies demonstrated a slightly larger subunit size of NC1 in PYS-2 cell culture and the rapid release of precursor-specific segments prior to secretion from the cells. Autoantibodies against mouse tumor NC1 were produced in mice and were detected both in the blood and as tissue-bound forms (kidney, lung). The autoantibody response is accompanied by certain pathological alterations mimicking Goodpasture's syndrome. The possible relationship between the two diseases is substantiated by reaction of Goodpasture antisera with the globular domain obtained from various tissue sources.

Animals↗