Biomedical subjects

Wilson Savino

Publications and source records attributed to Wilson Savino.

28 records · Page 2Linked to original sources

PubMed2003

Trypanosoma cruzi infection modulates intrathymic contents of extracellular matrix ligands and receptors and alters thymocyte migration.

Several T cell abnormalities have been described in the course of acute Trypanosoma cruzi infection in mice, including severe effects on the thymus. In the present study, looking at the expression of extracellular matrix ligands in the thymus, we observed that deposits of fibronectin and laminin increased progressively during the course of infection, reaching a maximum at the peak of parasitemia and thymic atrophy. Concomitantly, membrane expression of fibronectin and laminin receptors (VLA-4, VLA-5 and VLA-6) was also enhanced on thymocyte subsets of infected mice. These results correlated with changes in intrathymic thymocyte migration ability during the acute phase of infection, when a higher fibronectin-dependent transmigratory activity of CD4(+)CD8(+) thymocytes was observed. Strikingly, we detected higher frequency of immature and high VLA-expressing CD4(+)CD8(+) T cells in the peripheral lymphoid organs of infected mice at the peak of parasitemia. These cells seemed to be thymus dependent, since significantly lower amounts of them were found in thymectomized mice, and some of them carry "prohibited" Vbeta segments of the TCR. Our data suggest an imbalance in the intrathymic cell trafficking following acute T. cruzi infection, likely due to dysregulated extracellular matrix-dependent interactions.

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PubMed2003

Experimental Trypanosoma cruzi infection alters the shaping of the central and peripheral T-cell repertoire.

We investigated the thymic and peripheral T-lymphocyte subsets in BALB/c mice undergoing acute or chronic Trypanosoma cruzi infection, in terms of expression of particular Vbeta rearrangements of the T-cell receptor. We first confirmed the severe depletion of CD4(+)CD8(+) thymocytes following acute T. cruzi infection. By contrast, the numbers of CD4(+)CD8(+) cells in subcutaneous lymph nodes increased up to 16 times. In subcutaneous lymph nodes, we found CD4(+)CD8(+) cells that expressed prohibited segments TCRVbeta5 and TCRVbeta12 (which are physiologically deleted in the thymus of BALB/c mice), as did some mature single-positive cells (CD4(+)CD8(-) and CD4(-)CD8(+)). In the thymus of infected animals, although higher numbers of immature cells bearing such Vbeta segments were seen, they were no longer detected in the mature single-positive stage, suggesting that negative selection occurs normally. We also found increased numbers of cells bearing the potentially autoreactive phenotype TCRVbeta5(+) and TCRVbeta12(+) in T-lymphocyte subsets from subcutaneous lymph nodes of T. cruzi chronically infected mice. In conclusion, our data indicate that immature T lymphocytes bearing prohibited TCRVbeta segments leave the thymus and gain the lymph nodes, where they further differentiate into mature CD4(+) or CD8(+) cells. Conjointly, these findings show changes in the shaping of the central and peripheral T-cell repertoire in both acute and chronic phases of murine T. cruzi infection. The release of potentially autoreactive T cells in the periphery of the immune system may contribute to the autoimmune process found in both murine and human Chagas' disease.

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PubMed2003

In vivo effects of growth hormone on thymic cells.

Increasing evidence has placed the thymus as a target for neuroendocrine control. Herein we review the pleiotropic effects of growth hormone (GH) on this primary lymphoid organ, with emphasis on data derived from in vivo experiments. A series of results strongly indicate that GH enhances thymocyte proliferation in both rodents and humans. Moreover, in vivo treatment with GH enhances interleukin (IL)-6 production by mouse thymocytes, and ex vivo experiments show that production of other cytokines, such as IL-1 and GM-CSF, is also augmented. In a second vein, GH exerts a modulatory role on thymic hormone production, particularly the secretion of thymulin. In GH-treated animals as well as GH-transgenic mice, thymulin secretion is enhanced. In acromegalic patients we found higher levels of thymulin secretion, whereas the opposite was seen in dwarf mice and GH receptor knockout animals. Developing T cell migration is also under GH influence. Recombinant GH was found to increase human T cell engraftment in the thymus of SCID mice. Moreover, ex vivo thymocyte traffic into and out of thymic nurse cell complexes is enhanced after GH treatment. Lastly, we show that thymocyte export in vivo is modulated by GH, which favors the homing of CD4(+) recent thymic emigrants towards lymph nodes. In conclusion, the possibility that GH improves in vivo thymic functions, including thymocyte proliferation and migration, points to this molecule as a potential therapeutic adjuvant in T cell associated immunodeficiencies.

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PubMed2003

Late effects of the Chernobyl radiation accident on T cell-mediated immunity in cleanup workers.

The main goal of this investigation was to evaluate the abnormal T-cell immunity in cleanup workers who took part in the cleanup after the Chernobyl accident in 1986. Peripheral blood mononuclear cells (MNCs) of apparently healthy cleanup workers (n = 134) were used to analyze the phenotype and proliferative response to mitogens in vitro. Evaluation of the MNC phenotype of cleanup workers did not reveal a significant disturbance in the T-cell subpopulation content except for an increase in CD3+CD16+56+ (NKT) cells. Immunophenotyping of phytohemagglutinin (PHA)-activated MNCs demonstrated suppression of CD4+ T-cell propagation and augmentation of CD8+ T-cell propagation in vitro compared to control individuals. DNA synthesis in the MNCs of cleanup workers was markedly inhibited after activation for 3 days with suboptimal concentrations of PHA, pokeweed mitogen and PMA. In contrast to control individuals, the monocytes of cleanup workers were able to stimulate the proliferation of T cells from healthy individuals but inhibited the proliferation of T cells from cleanup workers. This study affords a better understanding of the response of MNCs to stimulation with suboptimal concentrations of PHA and provides an approach to a more accurate analysis of the immunological disorders found after exposure to radiation from Chernobyl-related activities.

Antigens, CD↗

PubMed2002

Local antilaminin antibody treatment alters the rejection pattern of murine cardiac allografts: correlation between cellular infiltration and extracellular matrix.

BACKGROUND: Emerging data place extracellular matrix (ECM) proteins as important elements in lymphocyte positioning and effector function in alloreactive responses. Using a non-vascularized model of allogeneic heart transplantation in Swiss mice, we have observed a correlation between the cellular infiltration and ECM deposition towards the interior of the graft during the kinetics of rejection. METHODS: To confirm the importance of ECM during the rejection process in this model, we treated the transplanted animals with local injections of antilaminin monoclonal antibody and analyzed, by histology and immunohistochemistry, the grafts on day 15, which corresponds to the peak of cellular infiltration and ECM deposition. RESULTS: The treatment with mAb antilaminin decreased the cellular infiltrate and ECM deposition within the grafts, as compared to controls. Moreover, we found a diminished IFN-gamma, TNF-alpha and IL-2 deposition in the transplant area, and a reduced co-localization of these cytokines with laminin. By contrast, the antilaminin treatment increased tenascin deposition, a molecule with immunosuppressive properties, and also caused an increase in apoptosis of the cellular infiltrate. CONCLUSIONS: These data hallmark the importance of laminin, in distinct aspects concerning the events leading to allograft rejection, and also reinforce this molecule as a potential target for immune intervention in organ transplantation.

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PubMed2002

Galectin-3 modulates carbohydrate-dependent thymocyte interactions with the thymic microenvironment.

The process of thymocyte differentiation occurs within the context of the thymic microenvironment, in which T cell precursors interact with thymic microenvironmental cells and extracellular matrix. Here we studied the expression of galectin-3, a beta-galactoside binding lectin, in the thymus of young adult mice. Galectin-3 was found mainly in the medulla and to a lesser extent in the cortex. We further showed that distinct microenvironmental elements, such as thymic epithelial cells, the epithelial component of thymic nurse complexes and phagocytic cells of the thymic reticulum produce, secrete and accumulate galectin-3 on the cell surface. Functionally, galectin-3-enriched medium inhibited in vitro thymocyte interactions with thymic microenvironmental cells, accelerated the release of thymocytes from thymic nurse cells and inhibited the reconstitution of these lymphoepithelial complexes. These effects were blocked by exogenous lactose (Galbeta1-4Glc), but not melibiose (Galalpha1-6Glc), and by a monospecific anti-galectin-3 antibody. Recombinant galectin-3 also inhibited thymocyte/thymic epithelial cell interactions. Our data indicate that intrathymically produced galectin-3 disrupts thymocyte/microenvironmental cell interactions, thus acting as a de-adhesion molecule.

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PubMed2002

Intrathymic T-cell migration: a combinatorial interplay of extracellular matrix and chemokines?

Cell migration is crucial for intrathymic T-cell differentiation. Chemokines and extracellular matrix proteins per se induce thymocyte migration, and recent data suggest a combinatorial role for these molecules in this event. For example, thymocyte migration induced by fibronectin plus CXCL12/SDF1-alpha (stromal cell-derived factor1-alpha) is higher than that elicited by the chemokine alone. If such interactions are relevant in the thymus, abnormal expression of any of these ligands and/or their corresponding receptors will lead to defects in thymocyte migration. At least in the murine model of Chagas disease, this seems to be the case. Therefore a better knowledge of this complex biological circuitry will provide new clues for understanding thymus physiology and designing therapeutic strategies targeting developing T cells.

Animals↗

PubMed2002

Resolution of skeletal muscle inflammation in mdx dystrophic mouse is accompanied by increased immunoglobulin and interferon-gamma production.

Mdx mouse, the animal model of Duchenne muscular dystrophy, develops an X-linked recessive inflammatory myopathy with an apparent sustained capacity for muscle regeneration. We analysed whether changes in the skeletal muscle during myonecrosis and regeneration would correlate with functional alterations in peripheral lymphoid tissues. Here we show that during the height of myonecrosis, mdx mice display marked atrophy of peripheral lymph nodes and extensive muscle inflammation. In contrast, enlargement of draining lymph nodes with accumulation of CD4+ CD44+, CD4+ CD25+, CD8+ CD44+ T lymphocytes and type-2 B cells was consistently observed during amelioration of the muscle lesion. In addition, regeneration of the muscular tissue was accompanied by concomitant increase of immunoglobulin-secreting cells in regional lymph nodes and bone marrow. Double immunolabelling analysis revealed intense B cell proliferation and formation of germinal centre in the follicles of dystrophic regional lymph nodes. Furthermore, lymph node cells produced large amounts of IFN-gamma but not IL-4, IL-6 or IL-10 after in vitro mitogen stimulation with Concanavalin A. As these alterations occurred mainly during the recovery period, we suggested that local activation of the immune system could be an influence which mitigates the myonecrosis of muscular tissue in the mdx dystrophic mouse.

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PubMed2002

Functional insulin-like growth factor-1/insulin-like growth factor-1 receptor-mediated circuit in human and murine thymic epithelial cells.

Interactions between thymocytes and thymic epithelial cell (TEC) can be modulated by growth hormone via insulin-like growth factor-1 (IGF-1). In this study, we showed IGF-1 and IGF-1 receptor mRNA expression by human and murine TEC and thymocytes. Functionally, IGF-1 stimulates extracellular matrix production by human TEC. Moreover, pretreatment of murine TEC with IGF-1 increases their adhesion to thymocytes. Interestingly, we observed an increase in the frequency of CD4-CD8-CD90+ T cells which adhered to pretreated TEC, supporting the concept that IGF-1 may also act indirectly on intrathymic T cell differentiation and migration through the thymic epithelium.

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PubMedDate not supplied

Triiodothyronine modulates extracellular matrix-mediated interactions between thymocytes and thymic microenvironmental cells.

OBJECTIVES: Thyroid hormones exert immunomodulatory activities and the thymus is one of their target organs. We previously showed that triiodothyronine (T(3)) modulates thymic hormone production and extracellular matrix (ECM) expression by mouse thymic epithelial cells (TEC). This concept is enlarged herein by studying the effects of T(3) in human TEC preparations including primary cultures derived from thymic nurse cell complexes, as well as human and murine TEC lines. METHODS AND RESULTS: We observed that in all cases, ECM ligands and receptors (such as fibronectin, laminin, VLA-5 and VLA-6) are enhanced in vitro, as ascertained by immunocytochemistry, ELISA and cytofluorometry. Moreover, thymocyte adhesion to these TEC preparations is augmented by T(3). Interestingly, TEC-thymocyte adhesion is also upregulated when thymocytes from T(3)-treated mice adhere to untreated TEC cultures. Such an enhancing effect of T(3) upon TEC-thymocyte interactions is likely due to the increase in the expression of ECM ligands and receptors, since it is prevented when T(3)-treated TEC cultures are incubated with anti-ECM antibodies prior to the adhesion assay. We then tested whether T(3) could modulate interactions between thymocytes and nonepithelial microenvironmental cells, exemplified herein by the phagocytic cells of the mouse thymic reticulum. In fact, in vitro treatment of these cells with T(3) increases ECM ligands and receptors and augments their ability to adhere to thymocytes. Lastly, using immunochemistry-based assays, we showed the presence of the nuclear T(3) receptor in all thymic microenvironmental cell preparations. CONCLUSION: Our data show that T(3) upregulates ECM-mediated heterocellular interactions of thymocytes with distinct thymic microenvironmental cells, in both humans and mice.

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