RESUMEN
TGF-ß is required for both Foxp3(+) regulatory T cell (Treg) and Th17 commitment. Plasmacytoid DCs (pDC) have been shown to participate to both Treg and Th17 commitment as well. However, few studies have evaluated the direct effect of TGF-ß on pDC, and to our knowledge, no study has assessed the capacity of TGF-ß-exposed pDC to polarize naive CD4(+) T cells. In this paper, we show that TGF-ß-treated pDC favor Th17 but not Treg commitment. This process involves a TGF-ß/Smad signal, because TGF-ß treatment induced Smad2 phosphorylation in pDC and blockade of TGF-ß signaling with the SD208 TGF-ßRI kinase inhibitor abrogated Th17 commitment induced by TGF-ß-treated pDC. Moreover, TGF-ß mRNA synthesis and active TGF-ß release were induced in TGF-ß-treated pDC and anti-TGF-ß Ab blocked Th17 commitment. Unexpectedly, TGF-ß treatment also induced increased IL-6 production by pDC, which serves as the other arm for Th17 commitment driven by TGF-ß-exposed pDC, because elimination of IL-6-mediated signal with either IL-6- or IL-6Rα-specific Abs prevented Th17 commitment. The in vivo pathogenic role of TGF-ß-treated pDC was further confirmed in the Th17-dependent collagen-induced arthritis model in which TGF-ß-treated pDC injection significantly increased arthritis severity and pathogenic Th17 cell accumulation in the draining lymph nodes. Thus, our data reveal a previously unrecognized effect of TGF-ß-rich environment on pDC ability to trigger Th17 commitment. Such findings have implications in the pathogenesis of autoimmune diseases or immune responses against mucosal extracellular pathogens.
Asunto(s)
Diferenciación Celular/efectos de los fármacos , Células Dendríticas/efectos de los fármacos , Células Th17/efectos de los fármacos , Factor de Crecimiento Transformador beta/farmacología , Animales , Artritis Experimental/inmunología , Artritis Experimental/metabolismo , Linfocitos T CD4-Positivos/efectos de los fármacos , Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD4-Positivos/metabolismo , Diferenciación Celular/inmunología , Células Dendríticas/inmunología , Células Dendríticas/metabolismo , Citometría de Flujo , Immunoblotting , Interleucina-17/metabolismo , Interleucina-6/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos DBA , Ratones Noqueados , Ratones Transgénicos , Fosforilación/efectos de los fármacos , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transducción de Señal/efectos de los fármacos , Transducción de Señal/inmunología , Proteína Smad2/metabolismo , Linfocitos T Reguladores/efectos de los fármacos , Linfocitos T Reguladores/inmunología , Linfocitos T Reguladores/metabolismo , Células Th17/inmunología , Células Th17/metabolismo , Factor de Crecimiento Transformador beta/genética , Factor de Crecimiento Transformador beta/metabolismoRESUMEN
BACKGROUND: The development of mucosal vaccines is crucial to efficiently control infectious agents for which mucosae are the primary site of entry. Major drawbacks of these protective strategies are the lack of effective mucosal adjuvant. Synthetic oligodeoxynucleotides that contain several unmethylated cytosine-guanine dinucleotide (CpG-ODN) motifs are now recognized as promising adjuvants displaying mucosal adjuvant activity through direct activation of TLR9-expressing cells. However, little is known about the efficacy of these molecules in stimulating the intestinal immune system in neonates. METHODOLOGY/PRINCIPAL FINDINGS: First, newborn mice received CpG-ODN orally, and the intestinal cytokine and chemokine response was measured. We observed that oral administration of CpG-ODN induces CXC and CC chemokine responses and a cellular infiltration in the intestine of neonates as detected by immunohistochemistry. We next compared the efficiency of the oral route to intraperitoneal administration in stimulating the intestinal immune responses of both adults and neonates. Neonates were more responsive to TLR9-stimulation than adults whatever the CpG-ODN administration route. Their intestinal epithelial cells (IECs) indirectly responded to TLR9 stimulation and contributed to the CXC chemokine response, whereas other TLR9-bearing cells of the lamina-propria produced CC chemokines and Th1-type cytokines. Moreover, we showed that the intestine of adult exhibited a significantly higher level of IL10 at homeostasis than neonates, which might be responsible for the unresponsiveness to TLR9-stimulation, as confirmed by our findings in IL10-deficient mice. CONCLUSIONS/SIGNIFICANCE: This is the first report that deciphers the role played by CpG-ODN in the intestine of neonates. This work clearly demonstrates that an intraperitoneal administration of CpG-ODN is more efficient in neonates than in adults to stimulate an intestinal chemokine response due to their lower IL-10 intestinal level. In addition we report the efficiency of the oral route at inducing intestinal chemokine responses in neonate that might be taken into consideration for further vaccine development against neonatal diseases.