Tolerance to lipopolysaccharide promotes an enhanced neutrophil extracellular traps formation leading to a more efficient bacterial clearance in mice

Tolerance to lipopolysaccharide (LPS) constitutes a stress adaptation, in which a primary contact with LPS results in a minimal response when a second exposure with the same stimulus occurs. However, active important defence mechanisms are mounted during the tolerant state. Our aim was to assess the contribution of polymorphonuclear neutrophils (PMN) in the clearance of bacterial infection in a mouse model of tolerance to LPS. After tolerance was developed, we investigated in vivo different mechanisms of bacterial clearance. The elimination of a locally induced polymicrobial challenge was more efficient in tolerant mice both in the presence or absence of local macrophages. This was related to a higher number of PMN migrating to the infectious site as a result of an increased number of PMN from the marginal pool with higher chemotactic capacity, not because of differences in their phagocytic activity or reactive species production. In vivo, neutrophils extracellular trap (NET) destruction by nuclease treatment abolished the observed increased clearance in tolerant but not in control mice. In line with this finding, in vitro NETs formation was higher in PMN from tolerant animals. These results indicate that the higher chemotactic response from an increased PMN marginal pool and the NETs enhanced forming capacity are the main mechanisms mediating bacterial clearance in tolerant mice. To sum up, far from being a lack of response, tolerance to LPS causes PMN priming effects which favour distant and local anti-infectious responses.Fil: Landoni, Verónica Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Chiarella, Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Martire Greco, Daiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Schierloh, Luis Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: van Rooijen, N.. University Of Amsterdam. Department of Molecular Biology; Países BajosFil: Rearte, María Bárbara. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Palermo, Marina Sandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Isturiz, Martín Amadeo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Fernández, Gabriela Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentin

Klebsiella pneumoniae ST258 Negatively Regulates the Oxidative Burst in Human Neutrophils

The epidemic clone of Klebsiella pneumoniae (Kpn), sequence type 258 (ST258), carbapenamase producer (KPC), commonly infects hospitalized patients that are left with scarce therapeutic option since carbapenems are last resort antibiotics for life-threatening bacterial infections. To improve prevention and treatment, we should better understand the biology of Kpn KPC ST258 infections. Our hypothesis was that Kpn KPC ST258 evade the first line of defense of innate immunity, the polymorphonuclear neutrophil (PMN), by decreasing its functional response. Therefore, our aim was to evaluate how the ST258 Kpn clone affects PMN responses, focusing on the respiratory burst, compared to another opportunistic pathogen, Escherichia coli (Eco). We found that Kpn KPC ST258 was unable to trigger bactericidal responses as reactive oxygen species (ROS) generation and NETosis, compared to the high induction observed with Eco, but both bacterial strains were similarly phagocytized and cause increases in cell size and CD11b expression. The absence of ROS induction was also observed with other Kpn ST258 strains negative for KPC. These results reflect certain selectivity in terms of the functions that are triggered in PMN by Kpn, which seems to evade specifically those responses critical for bacterial survival. In this sense, bactericidal mechanisms evasion was associated with a higher survival of Kpn KPC ST258 compared to Eco. To investigate the mechanisms and molecules involved in ROS inhibition, we used bacterial extracts (BE) and found that BE were able to inhibit ROS generation triggered by the well-known ROS inducer, fMLP. A sequence of experiments led us to elucidate that the polysaccharide part of LPS was responsible for this inhibition, whereas lipid A mediated the other responses that were not affected by bacteria, such as cell size increase and CD11b up-regulation. In conclusion, we unraveled a mechanism of immune evasion of Kpn KPC ST258, which may contribute to design more effective strategies for the treatment of these multi-resistant bacterial infections

Novel use of all-trans-retinoic acid in a model of lipopolysaccharide-immunosuppression to decrease the generation of myeloid-derived suppressor cells by reducing the proliferation of cd34+ precursor cells

All-trans-Retinoic Acid (ATRA) is a derivative of vitamin A with anti-proliferative properties. Endotoxin shock and subsequent immunosuppression (IS) by lipopolysaccharide (LPS) stimulates myelopoiesis with expansion of myeloid-derived suppressor cells (MDSC). Since we have previously shown that ATRA reverses the IS state by decreasing functional MDSC, our aim was to investigate if ATRA was able to modulate MDSC generation by regulating myelopoiesis in murine hematopoietic organs. We found that ATRA administration in vivo and in vitro decreased the number of CD34+ precursor cells that were increased in IS mice. When we studied the cellular mechanisms involved, we did not find any differences in apoptosis of CD34+ precursors or in the differentiation of these cells to their mature counterparts. Surprisingly, ATRA decreased precursor proliferation, in vitro and in vivo, as assessed by a reduction in the size and number of colony forming units (CFU) generated from CD34+ cells and by a decreased incorporation of H-thymidine. Moreover, ATRA administration to IS mice decreased the number of MDSC in the spleen, with a restoration of T lymphocyte proliferation and a restitution of the histological architecture. Our results indicate, for the first time, a new use of ATRA to abolish LPS-induced myelopoiesis, affecting the proliferation of precursor cells, and in consequence, decreasing MDSC generation, having a direct impact on the improvement of immune competence. Administration of ATRA could overcome the immunosuppressive state generated by sepsis that often leads to opportunistic life-threatening infections. Therefore, ATRA could be considered a complementary treatment to enhance immune responsesFil: Martire Greco, Daiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Rodriguez Rodrigues, Nahuel Emiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Castillo Montañez, Luis Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Vecchione, María Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: de Campos Nebel, Ildefonso Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Córdoba Moreno, Marlina Olyissa. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Meiss, Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Vermeulen, Elba Monica. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Landoni, Verónica Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Fernández, Gabriela Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentin

Integrin alpha-5 subunit is critical for the early stages of human pluripotent stem cell cardiac differentiation

The stem cell niche has a strong influence in the differentiation potential of human pluripotent stem cells with integrins playing a major role in communicating cells with the extracellular environment. However, it is not well understood how interactions between integrins and the extracellular matrix are involved in cardiac stem cell differentiation. To evaluate this, we performed a profile of integrins expression in two stages of cardiac differentiation: mesodermal progenitors and cardiomyocytes. We found an active regulation of the expression of different integrins during cardiac differentiation. In particular, integrin α5 subunit showed an increased expression in mesodermal progenitors, and a significant downregulation in cardiomyocytes. To analyze the effect of α5 subunit, we modified its expression by using a CRISPRi technique. After its downregulation, a significant impairment in the process of epithelial-to-mesenchymal transition was seen. Early mesoderm development was significantly affected due to a downregulation of key genes such as T Brachyury and TBX6. Furthermore, we observed that repression of integrin α5 during early stages led to a reduction in cardiomyocyte differentiation and impaired contractility. In summary, our results showed the link between changes in cell identity with the regulation of integrin α5 expression through the alteration of early stages of mesoderm commitment.Fil: Neiman, Gabriel. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Scarafia, Maria Agustina. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: la Greca, Alejandro Damián. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Santín Velazque, Natalia Lucía. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Garate, Ximena. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Waisman, Ariel. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Möbbs, Alan Miqueas. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Kasai-Brunswick, Tais Hanae. Universidade Federal do Rio de Janeiro; BrasilFil: Mesquita, Fernanda. Universidade Federal do Rio de Janeiro; BrasilFil: Martire Greco, Daiana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Academia Nacional de Medicina de Buenos Aires; ArgentinaFil: Moro, Lucía Natalia. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Luzzani, Carlos Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; ArgentinaFil: Bastos Carvalho, Adriana. Universidade Federal do Rio de Janeiro; BrasilFil: Sevlever, Gustavo. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; ArgentinaFil: Campos de Carvalho, Antonio. Universidade Federal do Rio de Janeiro; BrasilFil: Guberman, Alejandra Sonia. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Fisiología, Biología Molecular y Celular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Miriuka, Santiago Gabriel. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Immunomodulatory effects of All-Trans Retinoic Acid (ATRA) as a strategy for reversing the immunosuppression associated infections in a murine model

Las infecciones secundarias asociadas a estados de inmunosupresión en pacientes sépticos son la principal causa de muerte en las Unidades de Cuidados Intensivos. Por lo tanto, el desarrollo de estrategias enfocadas a utilizar drogas que reviertan este estado resulta prometedor. En este trabajo utilizamos el Ácido All-trans Retinoico (ATRA) para estudiar la modulación del estado inmunológico en un modelo murino de inmunosupresión (IS) por administración crónica de lipopolisacáridos. Demostramos un rol primordial de las células mieloides supresoras (Gr-1+ CD11b+ supresoras) en la inhibición de la proliferación T en los animales IS. Esta población adquiere sus propiedades inhibitorias en la médula ósea, y en el contexto de inmunosupresión, es direccionada a los ganglios linfáticos para ejercer su función. Asimismo, el ATRA evidenció claros efectos en el restablecimiento de la proliferación de linfocitos T, asociado a una disminución del número de Gr-1+ CD11b+ supresoras vivas en ganglios linfáticos, acompañado también de un aumento en los linfocitos T CD4+. Asimismo, demostramos que la administración del ATRA a los animales IS mejoró tanto la respuesta inmune innata, en términos de eliminación de un foco bacteriano, como la respuesta inmune humoral primaria. Nuestros resultados demuestran que el ATRA modula la respuesta inmune alterada en el estado de inmunosupresión actuando sobre distintos procesos y representa una estrategia posible para el tratamiento de pacientes sépticos que presenten un estado de inmunosupresión.Secondary infections associated with immunosuppressive states in septic patients are the leading cause of death in Intensive Care Units. Therefore, the development of strategies aimed at using drugs to reverse this state is promising. In this study we used All-Trans Retinoic Acid (ATRA) to study the modulation of the immune response in a murine model of immunosuppression (IS) by chronic administration of lipopolysaccharide. We demonstrated a key role of Myeloid Suppressor Cells (Gr-1+ CD11b+ suppressors) in the inhibition of T cell proliferation in IS animals. This population acquires its inhibitory properties in the bone marrow, and in the context of immunosuppression, migrates to the lymph nodes to exert its function. Furthermore, ATRA showed clear effects in restoring T cell proliferation associated with a decrease in the number of live Gr-1+ CD11b+ suppressor cells in lymph nodes, also accompanied by an increase in CD4 + lymphocytes. In addition, we showed that administration of ATRA to IS animals improved both the innate and immune response, in terms of bacterial clearance and the primary humoral immune response. Our results demonstrate that ATRA modulates the impaired immune response in LPS-induced immunosuppression acting on different processes, and represents a potential strategy for the treatment of septic patients with an immunosuppressive state.Fil:Martire Greco, Daiana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Efectos de la administración del ácido all trans retinoico (ATRA) en un modelo murino de inmunosupresión inducida por lipopolisacárido bacteriano

La exposición a lipopolisacáridos (LPS), el principal componente de la membrana de bacterias Gram-negativas, ha sido considerada la fase inicial y una de las causas de la inmunosupresión frecuentemente observada en la sepsis tardía. Las infecciones secundarias que se desarrollan debido a la inmuno-supresión post-sepsis son una causa importante de muerte en pacientes sépticos. Se sabe que la vitamina A (retinol) desempeña un papel esencial en el sistema inmunológico y puede ser importante para el funcionamiento óptimo del sistema inmune innato y adaptativo. La mayoría de los efectos de la vitamina A están mediados por el ácido all-trans retinoico (ATRA).Por otra parte, los ensayos clínicos han demostrado que el suplemento con vitamina A reduce la morbilidad y la mortalidad por diversas enfermedades infecciosas, y numerosos estudios en modelos animales han confirmado la capacidad de la vitamina A para prevenir las infecciones y fortalecer el sistema inmunológicoFil: Martire Greco, Daiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentin

Interleukin-10 controls human peripheral PMN activation triggered by lipopolysaccharide

Large amounts of anti-inflammatory mediators, such as interleukin (IL)-10, are produced and found early in the course of sepsis. We explore the role of IL-10 on neutrophil (PMN) activation/function using an in vitro model. Isolated human PMN were pre-incubated with polysaccharide (LPS) and/or IL-10 for 18 h. Subsequently, a second LPS exposure was performed and CD11b and CD66b up-regulation, and the reactive oxygen species (ROS) generation were measured 2 h later. We found that IL-10 prevented PMN activation and the secretion of TNF-a and IL-8 induced by the first LPS contact. In the absence of IL-10, a second LPS exposure induced additive effects that were prevented by IL-10. Only ROS generation was highly affected by the blockade of PMN-secreted TNF-a or IL-8. Additionally, IL-10 prevented other possible mechanisms of LPS priming. Therefore, IL-10 modulates PMN activation preventing autocrine activating loops and priming mechanisms, rendering PMN less responsive to a second LPS exposure.Fil: Martire Greco, Daiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Rodriguez Rodrigues, Nahuel Emiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Landoni, Verónica Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Rearte, María Bárbara. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Isturiz, Martín Amadeo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Fernández, Gabriela Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentin

all-trans-Retinoic acid improves immunocompetence in a murine model of lipopolysaccharide-induced immunosuppression

Abstract Secondary infections due to post-sepsis immunosuppression are a major cause of death in patients with sepsis. Strategies aimed at restoring immune functions offer a new perspective in the treatment of sepsis. In the present study, we used LPS (lipopolysaccharide)-immunosuppressed mice to analyse the effects of ATRA (all-trans retinoic acid) on different immune parameters. The IS (immunocompromised) group had decreased lymphocyte and increased MDSC (myeloid-derived suppressor cell) counts in lymph nodes. They also had an impaired in vitro T-cell proliferation, mediated by MDSCs. ATRA administration restored T-cell proliferation, which was associated with a decreased number of live MDSCs. The IS group treated with ATRA had an increased number of CD4 + and CD8 + T-cells. ATRA partially improved the primary humoral immune response, even when immunosuppression was established first and ATRA was administered subsequently. Our results demonstrate that ATRA restores immunocompetence by modulating the number of leucocytes and the survival of MDSCs, and thus represents an additional potential strategy in the treatment of the immunosuppressive state of sepsis

Modulation of neutrophil extracellular traps release by Klebsiella pneumoniae

One of the main bactericidal mechanisms of polymorphonuclear neutrophils (PMN) is the release of neutrophil extracellular traps (NETs), which capture and destroy pathogens. Klebsiella pneumoniae (Kpn) producer of carbapenemase (KPC) and belonging to the sequence type 258 (ST258), is a hyper epidemic clone that causes a large number of infections worldwide associated with high persistence and mortality. It is necessary to investigate the interaction of Kpn KPC with the immune system to improve prevention and treatment of infections mediated by this bacterium. Based on the hypothesis that Kpn is able to subvert PMN-mediated death, the aim was to assess whether Kpn KPC ST258 could modulate the bactericidal response of PMN, focusing on NETs formation, compared to another opportunistic pathogen, as Escherichia coli (Eco). The results showed that the release of NETs was absent when PMN were challenged with Kpn KPC, while Eco was a strong inducer of NETosis. Moreover, Kpn KPC was able to inhibit NETosis induced by Eco. The inhibition of Kpn KPC-mediated NETs formation still occurred in spite of exogenous addition of hydrogen peroxide (H2O2), did not involve bacterial-released soluble factors or cell wall components, and was dependent on bacterial viability. Moreover, when degranulation was investigated, we found that Kpn KPC affected only the mobilization of primary granules, which harbor the proteins with more potent bactericidal properties and those related to NETosis. In conclusion, Kpn KPC ST258 effectively managed to evade the PMN response by inhibiting the release of NETs, and primary granule mobilization.Fil: Birnberg Weiss, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Castillo, Luis A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Pittaluga, José R.. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Martire Greco, Daiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Gómez, Sonia Alejandra. Dirección Nacional de Institutos de Investigación. Administración Nacional de Laboratorios e Institutos de Salud. Instituto Nacional de Enfermedades Infecciosas. Área de Antimicrobianos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Landoni, Verónica Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Fernández, Gabriela Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentin

Immature myeloid Gr-1+ CD11b+ cells from lipopolysaccharide-immunosuppressed mice acquire inhibitory activity in the bone marrow and migrate to lymph nodes to exert their suppressive function

Secondary infections due to post-sepsis immunosuppression are a major cause of death in patients with sepsis.Repetitive inoculation of increasing doses of lipopolysaccharide (LPS) into mice mimics the immunosuppressionassociated with sepsis. Myeloid-derived suppressor cells (MDSCs, Gr-1+ CD11b+) are considered a majorcomponent of the immunosuppressive network, interfering with T-cell responses in many pathological conditions.We used LPS-immunosuppressed (IS) mice to address whether MDSCs acquired their suppressive ability in thebone marrow (BM) and whether they could migrate to lymph nodes (LNs) to exert their suppressive function. Ourresults showed that Gr-1+ CD11b+ cells of IS mice already had the potential to inhibit T-cell proliferation in the BM.Moreover, soluble factors present in the BM from IS mice were responsible for inducing this inhibitory ability incontrol BM cells. In addition, migration of Gr-1+ CD11b+ to LNs in vivo was maximal when cells obtained from theBM of IS mice were inoculated into an IS context. In this regard, we found chemoattractant activity in cell-free LNextracts (LNEs) from IS mice and an increased expression of the LN-homing chemokine receptor C?C chemokinereceptor type 7 (CCR7) in IS BM Gr-1+ CD11b+ cells. These results indicate that Gr-1+ CD11b+ cells found in BMfrom IS mice acquire their suppressive activity in the same niche where they are generated, and migrate to LNs toexert their inhibitory role. A better understanding of MDSC generation and/or regulation of factors able to inducetheir inhibitory function may provide new and more effective tools for the treatment of sepsis-associatedimmunosuppression.Fil: Landoni, Verónica Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Martire Greco, Daiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Rodriguez Rodrigues, Nahuel Emiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Chiarella, Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Schierloh, Luis Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Isturiz, Martín Amadeo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Fernández, Gabriela Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; Argentin