RESUMO
The intracellular signaling molecule TRAF6 is critical for Toll-like receptor (TLR)-mediated activation of dendritic cells (DCs). We now report that DC-specific deletion of TRAF6 (TRAF6ΔDC) resulted, unexpectedly, in loss of mucosal tolerance, characterized by spontaneous development of T helper 2 (Th2) cells in the lamina propria and eosinophilic enteritis and fibrosis in the small intestine. Loss of tolerance required the presence of gut commensal microbiota but was independent of DC-expressed MyD88. Further, TRAF6ΔDC mice exhibited decreased regulatory T (Treg) cell numbers in the small intestine and diminished induction of iTreg cells in response to model antigen. Evidence suggested that this defect was associated with diminished DC expression of interleukin-2 (IL-2). Finally, we demonstrate that aberrant Th2 cell-associated responses in TRAF6ΔDC mice could be mitigated via restoration of Treg cell activity. Collectively, our findings reveal a role for TRAF6 in directing DC maintenance of intestinal immune tolerance through balanced induction of Treg versus Th2 cell immunity.
Assuntos
Células Dendríticas/imunologia , Enterite/imunologia , Eosinofilia/imunologia , Eosinófilos/imunologia , Gastrite/imunologia , Intestinos/imunologia , Linfócitos T Reguladores/imunologia , Fator 6 Associado a Receptor de TNF/metabolismo , Células Th2/imunologia , Animais , Células Cultivadas , Células Dendríticas/microbiologia , Enterite/genética , Eosinofilia/genética , Gastrite/genética , Regulação da Expressão Gênica/genética , Regulação da Expressão Gênica/imunologia , Tolerância Imunológica/genética , Interleucina-2/genética , Interleucina-2/metabolismo , Intestinos/microbiologia , Intestinos/patologia , Ativação Linfocitária/genética , Metagenoma/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fator 88 de Diferenciação Mieloide/genética , Fator 88 de Diferenciação Mieloide/metabolismo , Transdução de Sinais/genética , Linfócitos T Reguladores/microbiologia , Fator 6 Associado a Receptor de TNF/genética , Fator 6 Associado a Receptor de TNF/imunologia , Células Th2/microbiologiaRESUMO
The inserted (I) domain of αLß2 integrin (LFA-1) contains the entire binding site of the molecule. It mediates both rolling and firm adhesion of leukocytes at sites of inflammation depending on the activation state of the integrin. The affinity change of the entire integrin can be mimicked by the I domain alone through mutations that affect the conformation of the molecule. High-affinity mutants of the I domain have been discovered previously using both rational design and directed evolution. We have found that binding affinity fails to dictate the behavior of I domain adhesion under shear flow. In order to better understand I domain adhesion, we have developed a novel panning method to separate yeast expressing a library of I domain variants on the surface by adhesion under flow. Using conditions analogous to those experienced by cells interacting with the post-capillary vascular endothelium, we have identified mutations supporting firm adhesion that are not found using typical directed evolution techniques that select for tight binding to soluble ligands. Mutants isolated using this method do not cluster with those found by sorting with soluble ligand. Furthermore, these mutants mediate shear-driven cell rolling dynamics decorrelated from binding affinity, as previously observed for I domains bearing engineered disulfide bridges to stabilize activated conformational states. Characterization of these mutants supports a greater understanding of the structure-function relationship of the αL I domain, and of the relationship between applied force and bioadhesion in a broader context.