RESUMO
Intestinal homeostasis relies on a continuous dialogue between the commensal bacteria and the immune system. Natural killer T (NKT) cells, which recognize CD1d-restricted microbial lipids and self-lipids, contribute to the regulation of mucosal immunity, yet the mechanisms underlying their functions remain poorly understood. Here, we demonstrate that NKT cells respond to intestinal lipids and CD11c+ cells (including dendritic cells (DCs) and macrophages) are essential to mediate lipid presentation within the gut ultimately controlling intestinal NKT cell homeostasis and activation. Conversely, CD1d and NKT cells participate in the control of the intestinal bacteria composition and compartmentalization, in the regulation of the IgA repertoire and in the induction of regulatory T cells within the gut. These changes in intestinal homeostasis require CD1d expression on DC/macrophage populations as mice with conditional deletion of CD1d on CD11c+ cells exhibit dysbiosis and altered immune homeostasis. These results unveil the importance of CD11c+ cells in controlling lipid-dependent immunity in the intestinal compartment and reveal an NKT cell-DC crosstalk as a key mechanism for the regulation of gut homeostasis.
Assuntos
Mucosa Intestinal/imunologia , Lipídeos de Membrana/imunologia , Células T Matadoras Naturais/imunologia , Linfócitos T Reguladores/imunologia , Animais , Antígenos CD1d/biossíntese , Antígenos CD1d/genética , Antígenos CD1d/imunologia , Antígeno CD11c/metabolismo , Células Dendríticas/imunologia , Disbiose/genética , Microbioma Gastrointestinal/imunologia , Imunoglobulina A/imunologia , Interleucina-4/imunologia , Mucosa Intestinal/microbiologia , Macrófagos/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos KnockoutRESUMO
The spatial distribution of signals downstream from receptor tyrosine kinases (RTKs) or G-protein coupled receptors (GPCR) regulates fundamental cellular processes that control cell migration and growth. Both pathways rely significantly on actin cytoskeleton reorganization mediated by nucleation-promoting factors such as the WASP-(Wiskott-Aldrich Syndrome Protein) family. WIP (WASP Interacting Protein) is essential for the formation of a class of polarised actin microdomain, namely dorsal ruffles, downstream of the RTK for PDGF (platelet-derived growth factor) but the underlying mechanism is poorly understood. Using lentivirally-reconstituted WIP-deficient murine fibroblasts we define the requirement for WIP interaction with N-WASP (neural WASP) and Nck for efficient dorsal ruffle formation and of WIP-Nck binding for fibroblast chemotaxis towards PDGF-AA. The formation of both circular dorsal ruffles in PDGF-AA-stimulated primary fibroblasts and lamellipodia in CXCL13-treated B lymphocytes are also compromised by WIP-deficiency. We provide data to show that a WIP-Nck signalling complex interacts with RTK to promote polarised actin remodelling in fibroblasts and provide the first evidence for WIP involvement in the control of migratory persistence in both mesenchymal (fibroblast) and amoeboid (B lymphocytes) motility.
Assuntos
Proteínas de Transporte/metabolismo , Estruturas da Membrana Celular/metabolismo , Movimento Celular , Proteína Neuronal da Síndrome de Wiskott-Aldrich/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Linfócitos B/citologia , Linfócitos B/efeitos dos fármacos , Linfócitos B/metabolismo , Western Blotting , Proteínas de Transporte/genética , Células Cultivadas , Quimiocina CXCL13/farmacologia , Quimiotaxia/efeitos dos fármacos , Proteínas do Citoesqueleto , Fibroblastos/citologia , Fibroblastos/efeitos dos fármacos , Fibroblastos/metabolismo , Camundongos , Camundongos da Linhagem 129 , Camundongos Knockout , Microscopia Confocal , Proteínas Oncogênicas/metabolismo , Fator de Crescimento Derivado de Plaquetas/farmacologia , Ligação Proteica , Pseudópodes/metabolismo , Receptores Proteína Tirosina Quinases/metabolismoRESUMO
Continuous migration of B cells at the follicle contrasts with their stable arrest after encounter with antigen. Two main ligand/receptor pairs are involved in these cell behaviors: the chemokine CXCL13/chemokine receptor CXCR5 and antigen/BCR. Little is known regarding the interplay between CXCR5 and BCR signaling in the modulation of B-cell dynamics and its effect on B-cell activation. We used a 2-dimensional model to study B-cell migration and antigen recognition in real time, and found that BCR signaling strength alters CXCL13-mediated migration, leading to a heterogeneous B-cell behavior pattern. In addition, we demonstrate that CXCL13/CXCR5 signaling does not impair BCR-triggered immune synapse formation and that CXCR5 is excluded from the central antigen cluster. CXCL13/CXCR5 signaling enhances BCR-mediated B-cell activation in at least 2 ways: (1) it assists antigen gathering at the synapse by promoting membrane ruffling and lymphocyte function-associated antigen 1 (LFA-1)-supported adhesion, and (2) it allows BCR signaling integration in motile B cells through establishment of LFA-1-supported migratory junctions. Both processes require functional actin cytoskeleton and non-muscle myosin II motor protein. Therefore, the CXCL13/CXCR5 signaling effect on shaping B-cell dynamics is an effective mechanism that enhances antigen encounter and BCR-triggered B-cell activation.