Characterization of a novel mouse cDNA, ES18, involved in apoptotic cell death of T-cells.
(1/2732)
Using the modified screening approach in combination with expressed sequence tags, we have identified several novel cDNAs from mouse embryonic stem (ES) cells, whose expression is tissue-restricted and/or developmentally regulated. One of the cDNAs, ES18, is preferentially expressed in lymph node and thymus, and contains noteworthy features of transcriptional regulator. The expression of ES18 transcript was selectively regulated during the apoptosis of T-cell thymoma S49.1 induced by several stimuli. Interestingly, the ES18 transcript was differently regulated in the mutually antagonistic process, between dexamethasone- and A23187-induced cell death of T-cells. Moreover, the message level of ES18 was selectively enhanced by staurosporine, a broad protein kinase inhibitor, but not by other protein kinase inhibitors such as GF109203X and H89. In addition, ES18 transcript was induced by C2-ceramide, which is a mediator of both dexamethasone- and staurosporine-induced apoptotic signaling. We further showed that transient overexpression of ES18 in mouse T-cell lymphoma increased the apoptotic cell death. These data suggest that ES18 may be selectively involved in specific apoptotic processes in mouse T-cells. (+info)
Targeted disruption of Smad3 reveals an essential role in transforming growth factor beta-mediated signal transduction.
(2/2732)
The Smads are a family of nine related proteins which function as signaling intermediates for the transforming growth factor beta (TGF-beta) superfamily of ligands. To discern the in vivo functions of one of these Smads, Smad3, we generated mice harboring a targeted disruption of this gene. Smad3 null mice, although smaller than wild-type littermates, are viable, survive to adulthood, and exhibit an early phenotype of forelimb malformation. To study the cellular functions of Smad3, we generated Smad3 null mouse embryonic fibroblasts (MEFs) and dermal fibroblasts. We demonstrate that null MEFs have lost the ability to form Smad-containing DNA binding complexes and are unable to induce transcription from the TGF-beta-responsive promoter construct, p3TP-lux. Using the primary dermal fibroblasts, we also demonstrate that Smad3 is integral for induction of endogenous plasminogen activator inhibitor 1. We subsequently demonstrate that Smad3 null MEFs are partially resistant to TGF-beta's antiproliferative effect, thus firmly establishing a role for Smad3 in TGF-beta-mediated growth inhibition. We next examined cells in which Smad3 is most highly expressed, specifically cells of immune origin. Although no specific developmental defect was detected in the immune system of the Smad3 null mice, a functional defect was observed in the ability of TGF-beta to inhibit the proliferation of splenocytes activated by specific stimuli. In addition, primary splenocytes display defects in TGF-beta-mediated repression of cytokine production. These data, taken together, establish a role for Smad3 in mediating the antiproliferative effects of TGF-beta and implicate Smad3 as a potential effector for TGF-beta in modulating immune system function. (+info)
Immunodeficiency syndrome in a 3-year-old llama.
(3/2732)
An adult, castrated male llama was presented for evaluation of a chronic respiratory problem. Complete blood analyses indicated a leukopenia and hypoproteinemia. Radial immunodiffusion, bone marrow core, and lymph node biopsies supported a tentative diagnosis of juvenile llama immunodeficiency syndrome. This diagnosis was confirmed by postmortem findings. (+info)
Developmental neurobiology: Alternative ends for a familiar story?
(4/2732)
Somatic DNA recombination is essential for production of functional antigen receptor genes of T and B lymphocytes, but it is thought to be unique to the immune system. Recent studies have now shown that recombination-related genes are also necessary for normal neuronal development. (+info)
Is gliadin mispresented to the immune system in coeliac disease? A hypothesis.
(5/2732)
The primary pathogenic trigger in coeliac disease (CD) is still unknown. We present the hypothesis that in CD the enterocytes could metabolize gliadin through an immunogenic pathway instead of a tolerogenic one. The result of this abnormal presentation of gliadin to the immune system would be the activation of lamina propria T cells, followed by the onset of enteropathy. (+info)
Development of T-B cell collaboration in neonatal mice.
(6/2732)
The neonatal immune response is impaired during the first weeks after birth. To obtain a better understanding of this immaturity, we investigated the development of T cell interactions with B cells in mice. For this purpose, we analyzed the immune response to three T-dependent antigens in vivo: (i) the polyclonal antibody response induced by vaccinia virus; (ii) the production of polyclonal and specific antibodies following immunization with hapten-carrier conjugates; (iii) the mouse mammary tumor virus superantigen (sAg) response involving an increase in sAg-reactive T cells and induction of polyclonal antibody production. After vaccinia virus injection into neonates, the polyclonal antibody response was similar to that observed in adult mice. The antibody response to hapten-carrier conjugates, however, was delayed and reduced. Injection with sAg-expressing B cells from neonatal or adult mice allowed us to determine whether B cells, T cells or both were implicated in the reduced immune response. In these sAg responses, neonatal T cells were stimulated by both neonatal and adult sAg-presenting B cells but only B cells from adult mice differentiated into IgM- and IgG-secreting plasma cells in the neonatal environment in vivo. Injecting neonatal B cells into adult mice did not induce antibody production. These results demonstrate that the environment of the neonatal lymph node is able to support a T and B cell response, and that immaturity of B cells plays a key role in the reduced immune response observed in the neonate. (+info)
Reduced immune function and malnutrition in the elderly.
(7/2732)
An important observation in elderly subjects is their susceptibility to infection associated with a decline in host immune function. Nutrition is also an important factor that influences host defense against infection. We, therefore, evaluated the relationship between nutritional status in 155 healthy subjects ranging in age from 20 to 99 years and various immunological parameters, including the phagocytic and bactericidal activities of neutrophils and monocytes, superoxide production and chemotaxis of neutrophils, lymphocyte subsets, blastoid transformation and serum immunoglobulins. Aging was associated with increased phagocytic activity of neutrophils but not bactericidal activity, superoxide production or chemotaxis of neutrophils. Aging was also associated with a significant decrease in the number of lymphocytes as well as a decline in mature T cells and helper/inducer T cells but with increased numbers of activated T cells, suppressor T cells and natural killer cells. In addition, blastoid transformation in response to phytohemagglutinin (PHA) and concanavalin A (Con A) was significantly reduced in aged subjects. A poor nutritional status was noted in individuals 60 years of age or older. The nutritional status did not influence neutrophil function but correlated significantly with the number of lymphocytes and degree of blastoid formation with PHA and Con A stimulation. Our results suggest that the cell-mediated immunity in elderly subjects is reduced as a result of malnutrition, and that improvement of the nutritional status may enhance the immune function, likely contributing to their successful aging. (+info)
Differential presentation of an altered peptide within fetal central and peripheral organs supports an avidity model for thymic T cell development and implies a peripheral readjustment for activation.
(8/2732)
Altered self peptides may drive T cell development by providing avidity of interactions low enough to potentiate positive selection but not powerful enough to trigger programmed cell death. Since the peptide repertoire in both central and peripheral organs is nearly the same, interactions of these peptides with T cells in the thymus would have to be different from those taking place in the periphery; otherwise, T cell development and maturation would result in either autoimmunity or T cell deficiency. Herein, a self and an altered self peptide were delivered to fetuses, and their presentation as well as the consequence of such presentation on T cell development were assessed. The results indicate that the self peptide was presented in both central and peripheral fetal organs and that such presentation abolished T cell responses to both peptides during adult life. However, the altered peptide, although presented in vivo as well as in vitro by splenic cells, was unable to stimulate a specific T cell clone when the presenting cells were of thymic origin and allowed offspring to be responsive to both peptides. These findings indicate that central and peripheral organs accommodate selection and peripheral survival of T cells by promoting differential altered peptide presentation. (+info)