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Biomedical subjects

S R Carding

Publications and source records attributed to S R Carding.

At least 37 records · Page 2Linked to original sources
PubMed1998

Lymphoid hyperplasia, autoimmunity, and compromised intestinal intraepithelial lymphocyte development in colitis-free gnotobiotic IL-2-deficient mice.

IL-2-deficient (IL-2(-/-)) mice develop disorders of the hemopoietic and immune systems characterized by anemia, lymphocytic hyperplasia, and colitis. The mechanisms responsible for these abnormalities remain unclear. To investigate the underlying basis of autoimmunity, the particular role of commensal gut flora in the initiation of colitis, and the role of IL-2 in the development of intestinal intraepithelial lymphocytes (iIEL), we evaluated IL-2(-/-) mice reared and maintained under gnotobiotic (germfree) conditions. By 8 wk of age, 80% (20 of 25) of germfree IL-2(-/-) mice show signs of disease, including anemia, disturbances in bone marrow hemopoietic cells, lymphocytic hyperplasia, and generalized autoimmunity, similar to those seen in specific pathogen-free (SPF) IL-2(-/-) mice. In striking contrast to SPF IL-2(-/-) mice, germfree IL-2(-/-) mice do not develop colitis. However, the numbers of gammadelta+ and TCR alphabeta+ CD8 alphaalpha+ iIELs are reduced, and in lethally irradiated SPF IL-2(+/+) mice, reconstituted with IL-2(-/-) bone marrow TCR gammadelta+ iIELs fail to develop, consistent with an important role of IL-2/IL-2R signaling in the development of gammadelta iIELs. Consequently, our findings demonstrate that the colitis seen in SPF IL-2(-/-) mice depends upon the presence of intestinal bacterial flora and that environmental Ags are not responsible for the anemia and extraintestinal lymphoid hyperplasia that occur in IL-2(-/-) mice. Thus, germfree IL-2(-/-) mice represent a unique system in which the role of IL-2 deficiency in hemopoietic and immune system disorders can be investigated in dissociation from complications that may arise due to colitis.

Age Factors↗
PubMed1998

Role of gamma delta T cells in immunity to infectious diseases and the regulation of hematolymphoid cell development.

My research interests are twofold. The first is to define the biochemical and molecular mechanisms that regulate hematopoietic cell development. In particular, the role that the cytokine interleukin-2 (IL2) plays in regulating the development and selection of lymphocyte progenitor cells, and in myelopoiesis are primary areas of research. The second is to understand the role that gamma delta T cells play in pathogen-induced immune responses and autoimmunity. Their involvement in the immune response to the intracellular bacteria Listeria monocytogenes in mice and Mycobacteria tuberculosis (Mtb) in humans, in T cell-mediated inflammatory bowel disease in humans, and the nature of the antigens they recognize during these responses are major areas of interest. Research material includes patient-derived tissues as well as both conventional and genetically engineered (transgenic) strains of mice.

Animals↗
PubMed1998

Canine X-linked severe combined immunodeficiency. A model for investigating the requirement for the common gamma chain (gamma c) in human lymphocyte development and function.

Our laboratory has identified and characterized an X-linked severe combined immunodeficiency (XSCID) in dogs that is due to mutations in the common gamma (gamma c) subunit of the interleukin-2 (IL2), IL4, IL7, IL9, and IL15 receptors. Canine XSCID, unlike genetically engineered gamma c-deficient mice, has a clinical and immunologic phenotype virtually identical to human XSCID. It appears that species-specific differences exist in the role of the gamma c and its associated cytokines in mice compared to their role in humans and dogs, suggesting gamma c-deficient dogs may be a more relevant model for studying the role of the gamma c in humans. We are utilizing this model for a variety of studies to address: 1. Fundamental questions concerning the role of the gamma c in cytokine regulation and lymphocyte development. 2. The pathogenesis of XSCID. 3. Strategies for improving bone marrow transplantation outcome. 4. Development and evaluation of strategies for gene therapy. 5. Human hematopoietic stem cell development.

Animals↗
PubMed1998

Thymic stromal-cell abnormalities and dysregulated T-cell development in IL-2-deficient mice.

The role that interleukin-2 (IL-2) plays in T-cell development is not known. To address this issue, we have investigated the nature of the abnormal thymic development and autoimmune disorders that occurs in IL-2-deficient (IL-2-/-) mice. After 4 to 5 weeks of birth, IL-2-/- mice progressively develop a thymic disorder resulting in the disruption of thymocyte maturation. This disorder is characterized by a dramatic reduction in cellularity, the selective loss of immature CD4-8- (double negative; DN) and CD4+8+ (double positive; DP) thymocytes and defects in the thymic stromal-cell compartment. Immunohistochemical staining of sections of thymuses from specific pathogen-free and germ-free IL-2-/- mice of various ages showed a progressive loss of cortical epithelial cells, MHC class II-expressing cells, monocytes, and macrophages. Reduced numbers of macrophages were apparent as early as 1 week after birth. Since IL-2-/- thymocyte progenitor populations could mature normally on transfer into a normal thymus, the thymic defect in IL-2-/- mice appears to be due to abnormalities among thymic stromal cells. These results underscore the role of IL-2 in maintaining functional microenvironments that are necessary to support thymocyte growth, development, and selection.

Animals↗
PubMed1998

Mechanisms of immune cell-mediated tissue injury in inflammatory bowel disease (Review).

This review discusses the mechanisms and pathways of immune cell-mediated intestinal inflammation and tissue injury in inflammatory bowel disease (IBD). Our lack of understanding of how the mucosal immune system normally functions to maintain the balance between tolerance and immunity to innumerable dietary and bacterial constituents of the gut is perhaps the biggest obstacle to understanding the cause(s) of IBD, and to developing more effective treatments for these debilitating disorders. Evidence that abnormalities or disruptions in the interaction of immune cells and gut bacteria can trigger or contribute to changes in the composition, regulation and activity of the mucosal immune system that result in inflammatory immune responses and tissue injury are discussed. Based upon these studies, we propose a model to explain how a breakdown in regulation and failure to resolve immune responses in the gut mucosa results in persistent activation of T lymphocytes and other immune cells and the uncontrolled production of soluble inflammatory mediators that directly or indirectly produce the pathophysiological changes and tissue injury characteristic of IBD.

Animals↗
PubMed1997

B7 blockade prevents activation-induced cell death of thymocytes.

Although both B7 and its counter-receptor CD28 are expressed in the thymus, the role of B7 in thymic selection is not clear. We investigated the role of B7 in intrathymic deletion of antigen-specific T cells using a TCR transgenic model specific for antigen ovalbumin (OVA) and H-2Ad. Intraperitoneal injection of OVA induced apoptosis of thymocytes and drastic reduction of thymocyte numbers. This was significantly inhibited by co-injection of CTLA-4-Ig which blocks B7 co-stimulation. Deletion of T cells in the thymus following i.p. injection of OVA was associated with T cell pre-activation as demonstrated by T cell proliferation and cytokine production. Injection of CTLA-4-Ig blocked all these activation events and rescued thymocytes from activation-induced cell death. These results demonstrate that B7 is required for the activation-induced cell death of MHC class II-restricted thymocytes in vivo.

Animals↗
PubMed1997

Changes in human mucosal gamma delta T cell repertoire and function associated with the disease process in inflammatory bowel disease.

BACKGROUND: Although gamma delta T cells are a major component of the human intestinal mucosa, it is not clear what role they play in mucosal immunity or if they are involved in the disease process of inflammatory bowel disease (IBD). MATERIALS AND METHODS: Flow cytometry and reverse transcriptase-polymerase chain reaction (RT-PCR) assays were used to identify quantitative and qualitative changes in the repertoire of gamma delta T cells present in surgical and/or biopsy samples or normal and inflamed colon from individual patients with ulcerative colitis (UC) or Crohn's disease (CD). Cytokine production and the ability to adhere to and interact with colonic fibroblasts were used to compare the functional properties of gamma delta T cells isolated from the normal and diseased colonic mucosa. RESULTS: Increased numbers of gamma delta T cells localized in areas of inflammation and tissue injury were found in the majority of patients, irrespective of the type of IBD present. This expansion was attributable to an increase in V delta 1+ cells expressing a V delta 1-(D delta 3)-J delta 1-encoded T cell receptor and was seen in patients with severe disease as well as those with newly diagnosed or less severe forms of IBD. Among T cells present in the inflamed mucosa of patients with CD, gamma delta T cells, particularly V delta 1+ cells, were a major source of the proinflammatory cytokine interferon-gamma and could interact with colonic fibroblasts. CONCLUSIONS: Our results demonstrate that the chronic inflammatory immune response characteristic of IBD is associated with distinct changes in the number, distribution, composition, and function of mucosal gamma delta T cells. Through the production of cytokines and physical interaction with other cells, gamma delta T cells can perform an immunoregulatory function and contribute to the pathophysiology of IBDs.

Adult↗
PubMed1996

Disease-specific changes in gammadelta T cell repertoire and function in patients with pulmonary tuberculosis.

Although gammadelta T cells are known to contain the highest frequency of mycobacteria-reactive cells in humans and numerous studies have suggested that they play an important role in the initial immune response to Mycobacterium tuberculosis (Mtb), very few studies have attempted to analyze these cells in patients with active pulmonary tuberculosis. The aim of the present study was therefore to evaluate the consequences of infection on the number and activity of mycobacteria-reactive gammadelta T cells. Three-color flow cytometric analysis of blood and bronchoalveolar lavage gammadelta T cells of patients diagnosed with active pulmonary tuberculosis showed that compared with normal healthy subjects and patients with the unrelated pulmonary granulomatous diseases sarcoidosis and berylliosis the size of the mycobacteria-reactive Vgamma9+/Vdelta2+ gammadelta T cell subset in both the blood and lung was dramatically reduced. In addition, the Vgamma9+/Vdelta2+ cells left intact in patients with tuberculosis were refractory to in vitro stimulation by Mtb Ags, which are potent stimuli for these cells in normal subjects. Our results demonstrate for the first time a strong correlation between the absence or loss of the major Vgamma9+/Vdelta2+ Mtb-reactive subset of gammadelta T cells and manifestations of disease, consistent with the hypothesis that these gammadelta T cells play a role in the protective immune response to Mtb infection.

Adult↗
PubMed1996

Extrathymic origin of human gamma delta T cells during fetal development.

We have identified the first TCRs to be generated in vivo during normal human fetal development. Before thymic formation, the liver is a site of generation for a subset of V gamma 9/V delta 2+ gamma delta T cells. Analysis of the expression of the male-specific gene, SRY, by V gamma 9/V delta 2+ gamma delta T cells isolated from the fetal liver of male donors has shown that these cells are generated de novo in the liver. Examination of TCR-V gamma and -V delta gene expression demonstrated that although multiple receptor rearrangements could be detected, V gamma 9-JP- and V delta 2-D delta 3-J delta 1/3-encoded receptors were preferentially expressed in each of five individual liver samples. Structural analysis of these receptor chains and those expressed by a panel of V gamma 9/V delta 2+ fetal T cell clones showed that the V gamma 9-JP receptors were invariant or canonical and that the delta-chains contained non-germ line-encoded structural motifs. gamma delta T cells expressing these structurally limited receptor chains were shown to be functional and capable of responding to mycobacterial Ags. Together with the observation that V gamma 9/V delta 2+ cells represented the majority of T cells present in the fetal liver between 7 and 11 wk of development, our findings demonstrate that this subset of gamma delta T cells is a major, and presumably important, component of the human fetal immune system.

Amino Acid Sequence↗
PubMed1996

Bias in the gamma delta T cell response to Listeria monocytogenes. V delta 6.3+ cells are a major component of the gamma delta T cell response to Listeria monocytogenes.

Despite extensive research, the role that gamma delta T cells play in the immune response to infectious disease has yet to be established. Here we report the generation of a mAb specific for the V delta 6.3 TCR and investigate the gamma delta+ and V delta 6.3+ T cell responses to the intracellular bacterium Listeria monocytogenes in BALB/c mice. By infecting animals with various doses of Listeria and analyzing the components of the cellular immune response at the two primary sites of infection, the liver and spleen, we have shown that the kinetics, composition, and magnitude of the gamma delta and V delta 6.3 T cell responses are dependent upon the injected dose of bacteria and the organ in which the infection is established. At low doses of infection, the gamma delta T cell response occurs late in the disease course, while at high doses, the response is earlier and of greater magnitude, particularly in the liver. At all infectious doses and in both tissues, the V delta 6.3+ population predominates and together with V delta 4+ cells composes the bulk of the gamma delta T cell response. Changes in the morphology of gamma delta+ and V delta 6.3+ cells at the site of infection are consistent with cellular activation and suggest that these cells are active participants in the Listeria-induced immune response. The results of our study suggest that many features of the gamma delta T cell response to Listeria are dose and tissue related.

Animals↗
PubMed1996

Activation and negative selection of functionally distinct subsets of antibody-secreting cells by influenza hemagglutinin as a viral and a neo-self antigen.

We have compared transgenic mice that express the influenza virus PR8 hemagglutinin (PR8 HA) as a membrane-bound neo-self antigen (HA104 mice) with nontransgenic (non-Tg) mice for their ability to generate HA-specific B cell responses after primary immunization with PR8 virus. HA-specific, IgM-secreting B cells were induced with similar frequencies in HA104 and non-Tg mice. In addition, a B cell clonotype (C4) that is characteristic of anti-HA immune responses of BALB/c mice was identified among HA-specific IgM hybridomas from HA104 mice. A subset of HA-specific, IgG-secreting B cells that arises rapidly after primary virus immunization in non-Tg mice, however, was substantially reduced in HA104 mice. Likewise, a B cell clonotype (C12) that dominates HA-specific IgG hybridomas generated after primary immunization of non-Tg mice was present at greatly reduced frequencies among hybridomas from HA104 mice. Because HA-specific, IgG-secreting B cells were generated by HA104 mice in response to a mutant HA containing an amino acid interchange in a B cell antigenic site, we conclude that these PR8 HA-specific, IgG-secreting B cells are negatively selected in HA104 mice as a result of their specificity for the neo-self PR8 HA. The findings demonstrate that HA-specific B cells that display distinct phenotypic potentials in non-Tg mice also differ in their susceptibility to negative selection from the primary B cell repertoire of HA104 mice: a subset of B cells that undergo rapid differentiation to become HA-specific IgG antibody-secreting cells (ASC) after activation in non-Tg mice is negatively selected in HA104 mice. By contrast, a subset that gives rise to HA-specific, IgM-secreting ASC persists in the primary repertoire of HA104 mice and can be activated by virus immunization.

Amino Acid Sequence↗
PubMed1996

Regulated expression and function of CD122 (interleukin-2/interleukin-15R-beta) during lymphoid development.

To determine whether signaling via CD122 (interleukin-2 [IL-2]/IL-15 receptor beta-chain) plays a role in regulating the expansion and differentiation of lymphocyte precursors, we have characterized its expression and evaluated its ability to influence the activity of developing lymphoid cells. A significant fraction of Sca1+Lin- hematopoietic stem cells in day 12 fetal liver were found to be CD122+. CD122-mRNA+ and IL-2-mRNA+ cells were also localized in embryo sections within pharyngeal blood vessels adjacent to and surrounding the thymic analgen. This distribution is consistent with the migration of CD122+ progenitor cells from the liver to the developing thymus where a majority of Sca1+ intrathymic T-cell progenitors were CD122+. Analysis of CD122 expression in the day 12 fetal liver revealed that the majority of B220+ cells were CD122+. Furthermore, CD122 expression was restricted to the earliest B220+ cells (CD43+CD24-; prepro B cells; fraction A) that proliferate vigorously to IL-2 in the absence of any stromal cells, but not to IL-15. Consistent with a role for the IL-2/IL-2R pathway in lymphocyte development is the progressive loss of B cells seen in IL-2-deficient mice. Together, these observations suggest that CD122 plays a role in regulating normal lymphocyte development in vivo.

Animals↗
PubMed1995

B7 costimulation is necessary for the activation of the lytic function in cytotoxic T lymphocyte precursors.

B7-CD28 costimulation is essential for the activation of CD4+ T helper cells, mainly by regulating IL-2 and other cytokine production. The requirement for this costimulatory pathway in the activation of CD8+ T cells, however, is still poorly understood. Here we analyzed the role of B7-CD28 costimulation in the differentiation of Ag-specific CTL precursor. We found that the activation of not only IL-2 production but also cytotoxic function in CD8 T cells requires B7 costimulation. The costimulatory signal, which cannot be replaced by exogenous IL-2, is directly implicated in the activation of the lytic machinery in CD8 T cells. Moreover, B7-CD28 costimulation appears to play a critical role in the accumulation of mRNA encoding at least one of the granzymes required for cytolytic function, granzyme B or CTLA-1. The production of IFN-gamma by CD8 T cells, however, does not appear to require costimulation.

Abatacept↗
PubMed1995

Gamma/delta T lymphocytes in viral infections.

T lymphocyte progenitors differentiate into two distinct T cell lineages. Although the alpha beta and gamma delta T cell lineages resemble each other phenotypically and functionally, there are some striking differences. Some gamma delta T cells recognize, similarly to alpha beta T cells, peptides presented by major histocompatibility complex (MHC) proteins or MHC-like molecules. However, there are gamma delta T cells that recognize MHC molecules in a fundamentally different manner in comparison with alpha beta T cells. Also in contrast recognizing nonpeptide antigens. Most responses of gamma delta T cells appear to be directed against microbial pathogenic agents including bacteria, parasites, and viruses. In particular, the potent cytotoxic responses of gamma delta T cells against cells infected with, for example, herpesviruses or lentiviruses may be essential for the overall antiviral defense of vertebrates. The analysis of antiviral immunosurveillance by gamma delta T cells is crucial for understanding the unique biological role of this lymphocyte subset.

Animals↗
PubMed1995

Low avidity recognition of a class II-restricted neo-self peptide by virus-specific T cells.

The specificity with which CD4+ T cells recognize self peptides in vivo was examined in transgenic mice that express an influenza virus PR8 hemagglutinin (HA) polypeptide in many tissues, including the thymus (HA Tg mice). HA Tg and non-Tg mice were analyzed for their T cell responses to the major PR8 HA I-E(d)-restricted CD4+ T cell determinant S1. Negative selection eliminated S1-specific T cells from HA Tg mice. Nevertheless, HA Tg mice retained the ability to mount a T cell response to a closely related analog of the S1 determinant [S1(K113)], and some S1(K113)-specific TCRs displayed a partial reactivity with S1 as indicated by their ability to transmit signals for IL-3 but not IL-2 secretion in response to the neo-self peptide. Moreover, the neo-self S1 peptide antagonized the ability of these TCRs to signal IL-2 secretion in response to the foreign S1(K113) determinant. Thus, TCRs that exhibit a partial reactivity with a self peptide are present in the peripheral T cell repertoire and can be activated by a virus containing an analog of the self peptide. These findings provide a model for the induction of autoimmunity by viruses that are close homologs of self peptides, and suggest a way in which TCRs could react with self peptides during positive selection of developing thymocytes.

Amino Acid Sequence↗
PubMed1993

The relationship of IL-4- and IFN gamma-producing T cells studied by lineage ablation of IL-4-producing cells.

Subsets of CD4 T cells are defined by the cytokines that they produce; these cytokines determine the effector function of these cells. Cloned CD4 T cells fall into two subsets, producing either interferon-gamma (IFN gamma) or interleukin-4 (IL-4) in combination with other cytokines, and are called Th1 and Th2 cells, respectively. The lineage relationship between naive T cells and effector Th1- and Th2-type cells is unclear. We generated transgenic mice in which IL-4-producing cells express herpes simplex virus 1 thymidine kinase and are eliminated by ganciclovir (GANC). Activation of transgenic T cells in the presence of GANC eliminates IL-4 and IFN gamma production, showing that IL-4- and IFN gamma-producing cells express or have expressed IL-4. These results show that effector cells producing either IL-4 or IFN gamma have a common precursor, which expresses the IL-4 gene.

Animals↗
PubMed1993

Liver gamma delta T cells. TCR junctions reveal differences in heat shock protein-60-reactive cells in liver and spleen.

The liver of mice contains elevated percentages of gamma delta T cells when compared with peripheral lymphoid organs. We have now analyzed these cells clonally, by generating a random collection of liver gamma delta T cell hybridomas and sequencing the productively rearranged TCR-gamma and -delta genes in each hybridoma clone. Examining C57BL/10 mice of various ages, we have found that over half of their normal gamma delta T cells are one of two types, V delta 4+ or V delta 6.3+. gamma delta T cell hybridomas generated from mouse liver contain clones that are "spontaneously" reactive, and respond to purified protein derivative from mycobacteria and to a 17-amino acid peptide from mycobacterial heat shock protein-60 (HSP-60). Like similar cells found in newborn thymus or adult spleen, all of the cells showing this HSP-60 reactivity pattern were found to express V gamma 1-J gamma 4-C gamma 4, most in conjunction with V delta 6-J delta 1-C delta, particularly with V delta 6.3. However, the gamma and delta junctional sequences of the V gamma 1/V delta 6+ cells isolated from adult liver differed from those found in adult spleen; being less diverse, their receptors instead resemble those of similar cells from newborn thymus. These data suggest that HSP-60-reactive gamma delta cells in adult murine liver and spleen are independent of each other and may be resident in their respective sites.

Amino Acid Sequence↗