CONICET | Buscador de Institutos y Recursos Humanos

Although much is described about the molecules involved in neutrophil migration from the circulation into tissues, less is known about the molecular mechanisms that regulate neutrophil entry into lymph nodes draining a local inflammatory site (dLN). The aim of this study was to determine if chemokine receptors are involved in neutrophil migration to dLN in a context of inflammation induced by immunization of BALB/c mice with ovalbumin (OVA) emulsified in Complete Freund?s Adjuvant (CFA). By confocal and flow cytometry analysis, we showed that neutrophils can enter dLN of OVA/CFA mice via lymphatic vessels and also from blood, across high endothelial venules. Additionally, we found that neutrophil migration to dLN could be abrogated by pertussis toxin treatment (p<0.001), demonstrating an involvement of G protein-coupled receptor signaling in this influx. Next, we sought to define which chemokine receptor could be implicated. ELISA assays of dLN homogenates showed that OVA challenge triggered the modulation of the expression of multiple chemokines in OVA/CFA mice (p<0.05). When we studied the expression of their specific receptors by flow cytometry, cell-surface analysis revealed that CXCR4 was the only chemokine receptor significantly up-regulated on blood neutrophils from OVA/CFA mice (p<0.01). Moreover, CXCR4 was also found in most of dLN-infiltrating neutrophils and also in those infiltrating the inflammatory site (p<0.05). To specifically demonstrate the role of CXCR4 in neutrophil migration to dLN, we performed adoptive transfer experiments to OVA/CFA mice which were treated with the CXCR4 inhibitor, AMD3100. Neutrophils displayed diminished migration to dLN from the inflammatory site and also from blood of AMD3100-treated mice (p<0.05). Taken together, these results identify CXCR4 as a chemokine receptor involved in the migration of neutrophils to dLN via blood and lymph.

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