RESUMEN
APRIL (A Proliferation-Inducing Ligand), a member of the TNF superfamily, was initially described for its ability to promote proliferation of tumor cells in vitro. Moreover, this cytokine has been related to the pathogenesis of different chronic inflammatory diseases, such as rheumatoid arthritis. This study aimed to evaluate the ability of APRIL in regulating B cell-mediated immune response in the antigen-induced arthritis (AIA) model in mice. AIA was induced in previously immunized APRIL-transgenic (Tg) mice and their littermates by administration of antigen (mBSA) into the knee joints. Different inflammatory cell populations in spleen and draining lymph nodes were analyzed using flow cytometry and the assay was performed in the acute and chronic phases of the disease, while cytokine levels were assessed by ELISA. In the acute AIA, APRIL-Tg mice developed a less severe condition and a smaller inflammatory infiltrate in articular tissues when compared with their littermates. We also observed that the total cellularity of draining lymph nodes was decreased in APRIL-Tg mice. Flow cytometry analysis revealed an increase of CD19+IgM+CD5+ cell population in draining lymph nodes and an increase of CD19+CD21hiCD23hi (B regulatory) cells in APRIL-Tg mice with arthritis as well as an increase of IL-10 and CXCL13 production in vitro.
Asunto(s)
Artritis Experimental , Linfocitos B Reguladores , Ratones Transgénicos , Miembro 13 de la Superfamilia de Ligandos de Factores de Necrosis Tumoral , Animales , Ratones , Artritis Experimental/inmunología , Artritis Experimental/patología , Linfocitos B Reguladores/inmunología , Interleucina-10/metabolismo , Ganglios Linfáticos/inmunología , Ganglios Linfáticos/patología , Bazo/inmunología , Miembro 13 de la Superfamilia de Ligandos de Factores de Necrosis Tumoral/metabolismo , Miembro 13 de la Superfamilia de Ligandos de Factores de Necrosis Tumoral/genéticaRESUMEN
Diabetes mellitus is a chronic disease that affects over 382 million people worldwide. Type-1 Diabetes (T1D) is classified as an autoimmune disease that results from pancreatic ß-cell destruction and insulin deficiency. Type-2 Diabetes (T2D) is characterized principally by insulin resistance in target tissues followed by decreased insulin production due to ß-cell failure. It is challenging to identify immunological markers such as inflammatory molecules that are triggered in response to changes during the pathogenesis of diabetes. APRIL is an important member of the TNF family and has been linked to chronic inflammatory processes of various diseases since its discovery in 1998. Therefore, this study aimed to evaluate APRIL serum levels in T1D and T2D. For this, we used the ELISA assay to measure serum APRIL levels of 33 T1D and 30 T2D patients, and non-diabetic subjects as control group. Our data showed a decrease in serum APRIL levels in T1D patients when compared with healthy individuals. The same pattern was observed in the group of T2D patients when compared with the control. The decrease of serum APRIL levels in diabetic patients suggests that this cytokine has a role in T1D and T2D. Diabetes is already considered as an inflammatory condition with different cytokines being implicated in its physiopathology. Our data suggest that APRIL can be considered as a potential modulating cytokine in the inflammatory process of diabetes.
Asunto(s)
Diabetes Mellitus Tipo 1/inmunología , Diabetes Mellitus Tipo 2/inmunología , Miembro 13 de la Superfamilia de Ligandos de Factores de Necrosis Tumoral/sangre , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Biomarcadores/sangre , Niño , Diabetes Mellitus Tipo 1/sangre , Diabetes Mellitus Tipo 2/sangre , Femenino , Humanos , Masculino , Persona de Mediana Edad , Adulto JovenRESUMEN
Wallerian degeneration (WD) comprises a series of events that includes activation of non-neuronal cells and recruitment of immune cells, creating an inflammatory milieu that leads to extensive nerve fragmentation and subsequent clearance of the myelin debris, both of which are necessary prerequisites for effective nerve regeneration. Previously, we documented accelerated axon regeneration in animals lacking galectin-3 (Gal-3), a molecule associated with myelin clearance. To clarify the mechanisms underlying this enhanced regeneration, we focus here on the early steps of WD following sciatic nerve crush in Gal-3(-/-) mice. Using an in vivo model of nerve degeneration, we observed that removal of myelin debris is more efficient in Gal-3(-/-) than in wild-type (WT) mice; we next used an in vitro phagocytosis assay to document that the phagocytic potential of macrophages and Schwann cells was enhanced in the Gal-3(-/-) mice. Moreover, both RNA and protein levels for the pro-inflammatory cytokines IL-1ß and TNF-α, as well as for Toll-like receptor (TLR)-2 and -4, show robust increases in injured nerves from Gal-3(-/-) mice compared to those from WT mice. Collectively, these data indicate that the lack of Gal-3 results in an augmented inflammatory profile that involves the TLR-cytokine pathway, and increases the phagocytic capacity of Schwann cells and macrophages, which ultimately contributes to speeding the course of WD.
Asunto(s)
Citocinas/metabolismo , Galectina 3/genética , Nervio Ciático/lesiones , Receptor Toll-Like 2/metabolismo , Receptor Toll-Like 4/metabolismo , Degeneración Walleriana/metabolismo , Animales , Citocinas/genética , Galectina 3/metabolismo , Macrófagos/metabolismo , Macrófagos/fisiología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Vaina de Mielina/metabolismo , Compresión Nerviosa , Fagocitosis , Células de Schwann/metabolismo , Células de Schwann/fisiología , Receptor Toll-Like 2/genética , Receptor Toll-Like 4/genética , Transcripción Genética , Degeneración Walleriana/genéticaRESUMEN
Trypanosoma cruzi acute infection leads to thymic atrophy, largely as a result of death of immature DP T cells. In a second vein, the glucocorticoid hormone imbalance promotes DP T cell apoptosis in infected mice. Herein, we assessed the involvement of caspase signaling in thymocyte death during T. cruzi acute infection. BALB/c mice were infected i.p. with 10(2) trypomastigote forms of T. cruzi and analyzed from 7 to 19 dpi. Thymocyte apoptosis was observed in early stages of infection, increasing along with time postinfection. Immature DN and DP as well as CD4(+) and CD8(+) thymocytes from infected mice showed increased activation of caspase-8, -9, and -3. In vitro treatment of thymocytes from infected mice with a general caspase inhibitor or the combination of caspase-8- and caspase-9-specific inhibitors increased the number of living thymocytes. Intrathymic injection of the general caspase inhibitor, but not caspase-8 or -9 inhibitors individually, prevented thymic atrophy and thymocyte depletion in infected mice. Moreover, blockade of glucocorticoid receptor activity with RU486 prevented DP thymocyte apoptosis, together with caspase-8 and -9 activation. These findings indicate that DP T cell apoptosis following experimental T. cruzi acute infection is dependent on glucocorticoid stimulation, promoting caspase-8 and -9 activation.
Asunto(s)
Caspasa 8/metabolismo , Caspasa 9/metabolismo , Enfermedad de Chagas/enzimología , Linfocitos T/patología , Animales , Apoptosis , Enfermedad de Chagas/inmunología , Enfermedad de Chagas/patología , Citometría de Flujo , Masculino , Ratones , Ratones Endogámicos BALB C , Linfocitos T/enzimología , Linfocitos T/parasitología , Timo/enzimología , Timo/inmunología , Timo/patología , Trypanosoma cruzi/inmunologíaRESUMEN
The thymus is a primary lymphoid organ in which bone marrow-derived T-cell precursors undergo differentiation, leading to migration of positively selected thymocytes to the T-cell-dependent areas of secondary lymphoid organs. This organ can undergo atrophy, caused by several endogenous and exogenous factors such as ageing, hormone fluctuations, and infectious agents. This paper will focus on emerging data on the thymic atrophy caused by infectious agents. We present data on the dynamics of thymus lymphocytes during acute Trypanosoma cruzi infection, showing that the resulting thymus atrophy comprises the abnormal release of thymic-derived T cells and may have an impact on host immune response.
RESUMEN
Little is known about the immunologic consequences from endocrine changes observed in diabetes. Since a preserved thymic microenvironment is of critical importance for the T cell development and maturation, we have examined the thymus from alloxan-diabetic mice. An intense thymic atrophy accompanied by changes in histological pattern and in thymocyte subpopulations were observed in diabetic mice. Laminin and fibronectin, which are closely associated with thymocytes maturation, were evaluated, but, only laminin presented an altered distribution and density in thymuses from diabetes group. the expression of fibronectin and laminin receptors was found to be decreased in diabetic mice. There was also intense decrease in the expression of two important chemokines for thymus, CCL25 and CXCL12, and in the CCR9 (CCL25 receptor), but the expression of CXCR4 (CXCL12 receptor) did not drop on cells. However, no significant difference was observed in the in vitro thymocytes migratory capacity from diabetic mice. The results show significant alterations in thymus microenvironment in diabetes and offer insights for studies involving endocrine influences on lymphatic organs and T cell maturation.
Asunto(s)
Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Tipo 1/metabolismo , Linfocitos T/metabolismo , Timo/metabolismo , Aloxano , Animales , Atrofia , Peso Corporal , Movimiento Celular , Supervivencia Celular , Quimiocina CXCL12/metabolismo , Quimiocinas CC/metabolismo , Diabetes Mellitus Experimental/inducido químicamente , Diabetes Mellitus Experimental/patología , Diabetes Mellitus Tipo 1/patología , Fibronectinas/metabolismo , Citometría de Flujo , Integrina alfa5beta1/metabolismo , Laminina/metabolismo , Masculino , Ratones , Ratones Endogámicos BALB C , Microscopía Fluorescente , Tamaño de los Órganos , Receptores CCR/metabolismo , Receptores de Laminina/metabolismo , Linfocitos T/patología , Timo/patologíaRESUMEN
Following infection, lymphocytes expand exponentially and differentiate into effector cells to control infection and coordinate the multiple effector arms of the immune response. Soon after this expansion, the majority of antigen-specific lymphocytes die, thus keeping homeostasis, and a small pool of memory cells develops, providing long-term immunity to subsequent reinfection. The extent of infection and rate of pathogen clearance are thought to determine both the magnitude of cell expansion and the homeostatic contraction to a stable number of memory cells. This straight correlation between the kinetics of T cell response and the dynamics of lymphoid tissue cell numbers is a constant feature in acute infections yielded by pathogens that are cleared during the course of response. However, the regional dynamics of the immune response mounted against pathogens that are able to establish a persistent infection remain poorly understood. Herein we discuss the differential lymphocyte dynamics in distinct central and peripheral lymphoid organs following acute infection by Trypanosoma cruzi, the causative agent of Chagas disease. While the thymus and mesenteric lymph nodes undergo a severe atrophy with massive lymphocyte depletion, the spleen and subcutaneous lymph nodes expand due to T and B cell activation/proliferation. These events are regulated by cytokines, as well as parasite-derived moieties. In this regard, identifying the molecular mechanisms underlying regional lymphocyte dynamics secondary to T. cruzi infection may hopefully contribute to the design of novel immune intervention strategies to control pathology in this infection.
Asunto(s)
Enfermedad de Chagas/inmunología , Trypanosoma cruzi/inmunología , Animales , Atrofia , Linfocitos B/inmunología , Proliferación Celular , Humanos , Ganglios Linfáticos/inmunología , Depleción Linfocítica , Bazo/inmunología , Linfocitos T/inmunología , Timo/inmunologíaRESUMEN
Thymocyte differentiation occurs within the thymic microenvironment, consisting of distinct cell types and extracellular matrix (ECM) elements. One of these ECM proteins is laminin. Previous experiments showed that laminin mediates interactions between thymocytes and thymic epithelial cells (TEC) in mice. Since, laminin comprises a family of related isoforms, we searched for laminin isoform expression in the human thymus. We found constitutive gene expression of various laminin chains in TEC preparations, comprising laminin-111 and laminin-211 isoforms. Immunocytochemistry revealed a selective laminin-211 distribution in the thymic lobules. In vitro functional assays revealed that laminin-211 enhances TEC/thymocyte adhesion and thymocyte release from thymic nurse cells, as well as the reconstitution of these complexes. Conversely, these interactions are blocked by monoclonal antibodies specific for laminin-211 and the laminin receptor VLA-6. Our results reinforce the notion that distinct laminin isoforms in the human thymus are relevant for lymphoepithelial interactions.
Asunto(s)
Comunicación Celular/inmunología , Diferenciación Celular/inmunología , Células Epiteliales/metabolismo , Laminina/metabolismo , Linfocitos T/metabolismo , Western Blotting , Adhesión Celular/inmunología , Movimiento Celular/inmunología , Preescolar , Células Epiteliales/inmunología , Expresión Génica , Humanos , Inmunohistoquímica , Lactante , Microscopía Confocal , Isoformas de Proteínas/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Linfocitos T/citología , Linfocitos T/inmunología , Timo/citología , Timo/inmunologíaRESUMEN
During acute infection with Trypanosoma cruzi, the causative agent of Chagas' disease, the thymus undergoes intense atrophy followed by a premature escape of CD4+CD8+ immature cortical thymocytes. Here we report a pivotal role for the endogenous lectin galectin-3 in accelerating death of thymocytes and migration of these cells away from the thymus after T. cruzi infection. We observed a pronounced increase in galectin-3 expression that paralleled the extensive depletion of CD4+CD8+ immature thymocytes after infection. In vitro, recombinant galectin-3 induced increased levels of death in cortical immature thymocytes. Consistent with the role of galectin-3 in promoting cell death, thymuses from gal-3-/- mice did not show cortical thymocyte depletion after parasite infection in vivo. In addition, galectin-3 accelerated laminin-driven CD4+CD8+ thymocyte migration in vitro and in vivo induced exportation of CD4+CD8+ cells from the thymus to the peripheral compartment. Our findings provide evidence of a novel role for galectin-3 in the regulation of thymus physiology and identify a potential mechanism based on protein-glycan interactions in thymic atrophy associated with acute T. cruzi infection.
Asunto(s)
Antígenos CD4/metabolismo , Antígenos CD8/metabolismo , Enfermedad de Chagas/metabolismo , Galectina 3/metabolismo , Timo/metabolismo , Trypanosoma cruzi , Animales , Atrofia/genética , Atrofia/metabolismo , Atrofia/patología , Muerte Celular/genética , Diferenciación Celular/genética , Enfermedad de Chagas/genética , Galectina 3/deficiencia , Regulación de la Expresión Génica/genética , Ratones , Ratones Endogámicos BALB C , Ratones Noqueados , Timo/parasitología , Timo/patologíaRESUMEN
Functional interactions between neuroendocrine and immune systems are mediated by similar ligands and receptors, which establish a bi-directional communication that is relevant for homeostasis. We investigated herein the hypothalamus-pituitary-adrenal (HPA) axis in mice acutely infected by Trypanosoma cruzi, the causative agent of Chagas' disease. Parasites were seen in the adrenal gland, whereas T. cruzi specific PCR gene amplification product was found in both adrenal and pituitary glands of infected mice. Histological and immunohistochemical analyses of pituitary and adrenal glands of infected animals revealed several alterations including vascular stasis, upregulation of the extracellular matrix proteins fibronectin and laminin, as well as T cell and macrophage infiltration. Functionally, we detected a decrease in CRH and an increase in corticosterone contents, in hypothalamus and serum respectively. In contrast, we did not find significant changes in the amounts of ACTH in sera of infected animals, whereas the serum levels of the glucocorticoid-stimulating cytokine, IL-6 (interleukin-6), were increased as compared to controls. When we analyzed the effects of T. cruzi in ACTH-producing AtT-20 cell line, infected cultures presented lower levels of ACTH and pro-opiomelanocortin production when compared to controls. In these cells we observed a strong phosphorylation of STAT-3, together with an increased synthesis of IL-6, suppressor of cytokine signaling 3 (SOCS-3) and inhibitor of activated STAT-3 (PIAS-3), which could explain the partial blockage of ACTH production. In conclusion, our data reveal that the HPA axis is altered during acute T. cruzi infection, suggesting direct and indirect influences of the parasite in the endocrine homeostasis.
Asunto(s)
Enfermedad de Chagas/fisiopatología , Sistema Hipotálamo-Hipofisario/microbiología , Sistema Hipófiso-Suprarrenal/microbiología , Glándulas Suprarrenales/microbiología , Glándulas Suprarrenales/fisiología , Hormona Adrenocorticotrópica/análisis , Hormona Adrenocorticotrópica/metabolismo , Animales , Corticosterona/análisis , Corticosterona/metabolismo , Hormona Liberadora de Corticotropina/análisis , Hormona Liberadora de Corticotropina/metabolismo , Sistema Hipotálamo-Hipofisario/fisiología , Hipotálamo/microbiología , Hipotálamo/fisiología , Immunoblotting , Inmunohistoquímica , Interleucina-6/análisis , Interleucina-6/metabolismo , Masculino , Ratones , Ratones Endogámicos BALB C , Hipófisis/microbiología , Hipófisis/fisiología , Sistema Hipófiso-Suprarrenal/metabolismo , Proteínas Inhibidoras de STAT Activados/análisis , Proteínas Inhibidoras de STAT Activados/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factor de Transcripción STAT3/análisis , Factor de Transcripción STAT3/metabolismo , Proteína 3 Supresora de la Señalización de Citocinas , Proteínas Supresoras de la Señalización de Citocinas/análisis , Proteínas Supresoras de la Señalización de Citocinas/metabolismo , Trypanosoma cruziRESUMEN
Previous evidence indicates that GH modulates thymic cell migration. In this study we approached this issue in vivo, studying thymocyte migration in GH transgenic animals and in normal mice treated intrathymically with GH. Extracellular matrix and chemokines are involved in thymocyte migration. In this respect, thymocyte adhesion to laminin was higher in GH-treated animals than controls, and the numbers of migrating cells in laminin-coated Transwells was higher in GH-transgenic and GH-injected mice. Additionally, CXC chemokine ligand 12 (CXCL12)-driven migration was higher in GH-Tg and GH-treated animals compared with controls. Interestingly, although CXCR4 expression on thymocytes did not change in GH-Tg mice, the CXCL12 intrathymic contents were higher. We found that CXCL12, in conjunction with laminin, would additionally enhance the migration of thymocytes previously exposed to high concentrations of GH in vivo. Lastly, there was an augmentation of recent thymic emigrants in lymph nodes from GH-Tg and GH-injected animals. In conclusion, enhanced thymocyte migration in GH transgenic mice as well as GH-injected mice results at least partially from a combined action of laminin and CXCL12. Considering that GH is presently being used as an adjuvant therapeutic agent in immunodeficiencies, including AIDS, the concepts defined herein provide important background knowledge for future GH-based immune interventions.
Asunto(s)
Quimiocinas CXC/farmacología , Hormona del Crecimiento/farmacología , Laminina/farmacología , Timo/citología , Timo/fisiología , Animales , Animales Modificados Genéticamente , Bovinos , Adhesión Celular/efectos de los fármacos , Movimiento Celular/efectos de los fármacos , Quimiocina CXCL12 , Sinergismo Farmacológico , Matriz Extracelular/metabolismo , Femenino , Hormona del Crecimiento/administración & dosificación , Hormona del Crecimiento/genética , Inyecciones , Ligandos , Ganglios Linfáticos/citología , Masculino , Ratones , Ratones Endogámicos BALB C , Receptores de Superficie Celular/metabolismo , Proteínas Recombinantes/administración & dosificación , Proteínas Recombinantes/farmacología , Timo/efectos de los fármacosRESUMEN
We previously showed that, in the context of thymic epithelial cells, thymocyte migration is partially controlled by extracellular matrix (ECM)-mediated interactions. Herein we evaluated whether these interactions could be involved in cell migration related events in the context of non-epithelial cells of the thymic microenvironment, the phagocytic cells of the thymic reticulum (PTR). We first showed, by immunocytochemistry, cytofluorometry, and RT-PCR, that PTR produce ECM components, including fibronectin and laminin, and express the corresponding integrin-type receptors, VLA-4, VLA-5, and VLA-6. Thymocytes adhere onto PTR monolayers, with immature CD4(+)CD8(+) cells being predominant. Importantly, such an adhesion is partially mediated by ECM ligands and receptors, since it was impaired by anti-ECM or anti-ECM receptor antibodies. Conjointly, our data reveal that the ECM-dependence for thymocyte adhesion onto the thymic microenvironment is not restricted to the epithelial cells, being also seen when they encounter non-epithelial phagocytic cells.
Asunto(s)
Comunicación Celular/fisiología , Matriz Extracelular/fisiología , Fagocitos/fisiología , Timo/fisiología , Animales , Adhesión Celular/fisiología , Movimiento Celular/fisiología , Femenino , Ligandos , Ratones , Ratones Endogámicos BALB CRESUMEN
We previously showed intrathymic alterations in non-obese diabetic (NOD) mice, including the appearance of giant perivascular spaces, filled with mature thymocytes, intermingled with an extracellular matrix network. This raised the hypothesis of a defect in thymocyte migration with partial arrest of exiting thymocytes in the perivascular spaces. Herein, we investigated the expression of receptors for fibronectin [very late antigen (VLA)-4 and VLA-5] and laminin (VLA-6), known to play a role in thymocyte migration. When compared with two normal and one other autoimmune mouse strains, a decrease of VLA-5 expression in NOD thymocytes was noticed, being firstly observed in late CD4/CD8 double-negative cells, and more pronounced in mature CD4(+) and CD8(+) thymocytes. Functionally, thymocyte exit from the lymphoepithelial complexes, the thymic nurse cells, was reduced. Moreover, NOD thymocyte adhesion to thymic epithelial cells as well as to fibronectin was diminished, and so was the migration of NOD thymocytes through fibronectin-containing transwell chambers. In situ, intra-perivascular space thymocytes were VLA-5-negative, suggesting a correlation between the thymocyte arrest within these structures and loss of VLA-5 expression. Overall, our data reveal impairment in NOD thymocyte migration, and correspond to the first demonstration of a functional fibronectin receptor defect in the immune system.
Asunto(s)
Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD8-positivos/inmunología , Movimiento Celular/inmunología , Receptores de Fibronectina/inmunología , Receptores de Laminina/inmunología , Timo/citología , Animales , Linfocitos T CD4-Positivos/citología , Linfocitos T CD4-Positivos/metabolismo , Linfocitos T CD8-positivos/citología , Linfocitos T CD8-positivos/metabolismo , Adhesión Celular/inmunología , Cruzamientos Genéticos , Femenino , Citometría de Flujo , Regulación de la Expresión Génica/inmunología , Masculino , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Ratones Endogámicos NOD , ARN/química , ARN/genética , Receptores de Fibronectina/biosíntesis , Receptores de Fibronectina/genética , Receptores de Laminina/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Organismos Libres de Patógenos Específicos , Timo/inmunología , Timo/metabolismoRESUMEN
Cell migration is crucial for thymocyte differentiation, and the cellular interactions involved now begin to be unraveled, with chemokines, extracellular matrix (ECM) proteins, and their corresponding receptors being relevant in such oriented movement of thymocytes. This notion derives from in vitro, ex vivo, and in vivo experimental data, including those obtained in genetically engineered and spontaneous mutant mice. Thymic microenvironmental cells produce both groups of molecules, whereas developing thymocytes express chemokine and ECM receptors. It is important that although chemokines and ECM proteins can drive thymocyte migration per se, a combined role of these molecules likely concurs for the resulting migration patterns of thymocytes in their various differentiation stages. In this respect, among ECM moieties, there are proteins with opposing functions, such as laminin or fibronectin versus galectin-3, which promote, respectively, adhesion and de-adhesion of thymocytes to the thymic microenvironment. How chemokines and ECM are produced and degraded remains to be more clearly defined. Nevertheless, matrix metalloproteinases (MMPs) likely play a role in the intrathymic ECM breakdown. It is interesting that these molecules also degrade chemokines. Thus, the physiological migration of thymocytes should be conceived as a resulting vector of multiple, simultaneous, or sequential stimuli, involving chemokines, adhesive, and de-adhesive ECM proteins. Moreover, these interactions may be physiologically regulated in situ by matrix MMPs and are influenced by hormones. Accordingly, one can predict that pathological changes in any of these loops may result in abnormal thymocyte migration. This actually occurs in the murine infection by the protozoan Trypanosoma cruzi, the causative agent of Chagas disease. In this model, the abnormal release of immature thymocytes to peripheral lymphoid organs is correlated with the higher migratory response to ECM and chemokines. Lastly, the fine dissection of the mechanisms governing thymocyte migration will provide new clues for designing therapeutic strategies targeting developing T cells. The most important function of the thymus is to generate T lymphocytes, which once leaving the organ, are able to colonize specific regions of peripheral lymphoid organs, the T cell zones, where they can mount and regulate cell-mediated, immune responses. This intrathymic T cell differentiation is a complex sequence of biological events, comprising cell proliferation, differential membrane protein expression, gene rearrangements, massive programmed cell death, and cell migration. In this review, we will focus on the mechanisms involved in controlling the migration of thymocytes, from the entrance of cell precursors into the organ to the exit of mature T cells toward peripheral lymphoid organs. Nevertheless, to better comprehend this issue, it appeared worthwhile to briefly comment on some key aspects of thymocyte differentiation and the tissue context in which it takes place, the thymic microenvironment.
Asunto(s)
Movimiento Celular/fisiología , Quimiocinas/fisiología , Matriz Extracelular/fisiología , Integrinas/fisiología , Linfocitos T/fisiología , Timo/citología , Animales , Adhesión Celular , Comunicación Celular , Diferenciación Celular , Humanos , Timo/fisiologíaRESUMEN
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.
Asunto(s)
Movimiento Celular/fisiología , Enfermedad de Chagas/metabolismo , Timo/metabolismo , Trypanosoma cruzi/patogenicidad , Animales , Linfocitos T CD4-Positivos/metabolismo , Linfocitos T CD8-positivos/metabolismo , Matriz Extracelular/metabolismo , Ratones , Receptores de Citoadhesina/biosíntesis , Receptores de Citoadhesina/genéticaRESUMEN
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.
Asunto(s)
Comunicación Celular/inmunología , Células Epiteliales/metabolismo , Matriz Extracelular/metabolismo , Células Madre/metabolismo , Linfocitos T/metabolismo , Timo/metabolismo , Triyodotironina/metabolismo , Animales , Adhesión Celular/efectos de los fármacos , Adhesión Celular/inmunología , Comunicación Celular/efectos de los fármacos , Células Cultivadas , Preescolar , Células Epiteliales/citología , Células Epiteliales/efectos de los fármacos , Matriz Extracelular/efectos de los fármacos , Proteínas de la Matriz Extracelular/efectos de los fármacos , Proteínas de la Matriz Extracelular/metabolismo , Femenino , Humanos , Inmunohistoquímica , Lactante , Recién Nacido , Ratones , Ratones Endogámicos BALB C , Receptores Mensajeros de Linfocitos/efectos de los fármacos , Receptores Mensajeros de Linfocitos/metabolismo , Receptores de Hormona Tiroidea/metabolismo , Células Madre/citología , Células Madre/efectos de los fármacos , Linfocitos T/citología , Linfocitos T/efectos de los fármacos , Timo/citología , Timo/efectos de los fármacos , Triyodotironina/farmacologíaRESUMEN
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.
Asunto(s)
Antígenos de Diferenciación/inmunología , Linfocitos T/inmunología , Linfocitos T/metabolismo , Timo/citología , Timo/metabolismo , Animales , Antígenos de Diferenciación/metabolismo , Antígenos de Diferenciación/farmacología , Metabolismo de los Hidratos de Carbono , Comunicación Celular , Diferenciación Celular , Galectina 3 , Técnicas In Vitro , Lactosa/farmacología , Melibiosa/farmacología , Ratones , Ratones Endogámicos BALB C , Fagocitos/inmunología , Proteínas Recombinantes/farmacología , Linfocitos T/citología , Linfocitos T/efectos de los fármacos , Timo/efectos de los fármacos , Timo/inmunología , Distribución TisularRESUMEN
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.