Rheumatoid synovium is enriched in mature antigen-presenting dendritic cells.
ABSTRACT Monocytes and dendritic cells (DC) can be purified from fresh peripheral blood (PB) based on their expression of CD33, CD13, and CD14. Whereas DC can be identified as CD33+ CD14dim or CD13+CD14dim cells, monocytes can be identified as CD33+CD14bright or CD13+CD14bright cells. Rheumatoid synovial fluid (SF) and synovial tissue (ST) non-T cells were found to be enriched in CD33+CD14dim cells compared with PB. Whereas 4 to 14% of normal or rheumatoid PB non-T cells were CD33+ and CD14dim, in rheumatoid SF or ST these cells comprised 20 to 45% of non-T mononuclear cells. Synovial CD33+CD14dim cells assumed a typical dendritic morphology on in vitro culture. Freshly isolated CD33+CD14dim PB DC precursors express low levels of HLA-DQ, CD40, and B7, which increase after in vitro incubation. In contrast, freshly isolated SF DC constitutively expressed these markers, and increased densities of HLA-DR and MHC class I molecules. Rheumatoid SF DC showed a specifically enhanced ability to stimulate autologous PB T cells compared with PB DC, or PB or SF monocytes. PB DC or monocytes preincubated in granulocyte-macrophage-CSF, TNF-alpha, or both cytokines exhibited enhanced expression of HLA-DR. Furthermore, DC preincubated in both granulocyte-macrophage-CSF and TNF-alpha were better stimulators of the autologous MLR than DC preincubated in medium, or in either cytokine alone. The data indicate that DC are enriched in rheumatoid SF and ST, and display a more differentiated phenotype than PB DC. These results suggest that PB DC accumulate in the synovium where they undergo phenotypic and functional differentiation in situ, which may be mediated by local cytokines. DC may play an important role in the ongoing presentation of antigen to autoreactive T cells in RA synovium.
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ABSTRACT: IntroductionThis study aimed to investigate PD-1/PD-L1 involvement in the hypo-responsiveness of rheumatoid arthritis (RA) synovial fluid CD4 T cells upon stimulation by (thymic stromal lymphopoietin (TSLP)-primed) CD1c myeloid dendritic cells (mDCs).Methods Expression of PD-1 on naïve (Tn), central memory (Tcm), and effector memory (Tem) CD4 T cell subsets was assessed by flow cytometry. PD-L1 expression and its regulation upon TSLP stimulation of mDCs from peripheral blood (PB) and synovial fluid (SF) of RA patients were investigated by quantitative reverse transcription polymerase chain reaction and flow cytometry. The involvement of PD-1/PD-L1 interactions in SF T cell hypo-responsiveness upon (TSLP-primed) mDC activation was determined by cell culture in the presence of PD-1 blocking antibodies, with or without interleukin 7 (IL-7) as recognized suppressor of PD-1 expression.ResultsPD-1 expression was increased on CD4 T cells derived from SF compared with PB of RA patients. TSLP increased PD-L1 mRNA expression in both PB and SF mDCs. PD-L1 protein expression was increased on SF mDCs compared with PB mDCs and was associated with T cell hypo-responsiveness. Blockade of PD-1, as well as IL-7 stimulation, during co-cultures of memory T cells and (TSLP-primed) mDCs from RA patients significantly recovered T cell proliferation.ConclusionSF T cell hypo-responsiveness upon (TSLP-primed) mDC stimulation in RA joints is partially dependent on PD-1/PD-L1 interactions as PD-1 and PD-L1 are both highly expressed on SF T cells and mDCs, respectively, and inhibiting PD-1 availability restores T cell proliferation. The potential of IL-7 to robustly reverse this hypo-responsiveness suggest that such proinflammatory cytokines in RA joints strongly contribute to memory T cell activation.Arthritis research & therapy. 11/2014; 16(6):497.
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ABSTRACT: Dendritic cells (DCs) are antigen presenting cells that activate T cells and determine the outcome of immune response. In addition to their important function in defense against pathogens, DCs are increasingly recognized as playing a crucial role in the regulation of immune tolerance. Plasticity of DCs with different maturity status and functions enable them to be exploited as potential cell-based therapy to restore immune tolerance in autoimmune diseases. Various ex vivo methods have been developed to generate stable tolerogenic DCs that are able to induce and maintain regulatory T cell homeostasis. The beneficial effect of tolerogenic DCs have been studied in murine autoimmune models with promising results. Systemic lupus erythematosus (SLE) is a prototypic multi-systemic autoimmune disease characterized by autoantibody production and deposition of immune complexes in organs. There are evidences that dysregulated DCs play a pivotal role in the initiation and perpetuation of lupus disease. Peripheral blood monocytes in SLE patients were found to have active phenotype with accelerated differentiation into DCs efficient in antigen presentation. Plasmacytoid DCs in SLE patients produce high levels of interferon-alpha, the signature cytokine of this disease, that cause a positive feedback loop in the amplification of activation of innate and adaptive immunity. Furthermore, manipulation of DCs via toll-like receptor knockout in a murine lupus model leads to alteration in disease severity and survival. Thus, tolerogenic DCs may appear as a potential cell-based therapeutic option in SLE.International Journal of Rheumatic Diseases 12/2014; · 1.65 Impact Factor
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ABSTRACT: Contact hypersensitivity (CHS) induced by topical application of haptens is a commonly used model to study dermal inflammatory responses in mice. Several recent studies have indicated that CHS-induced skin inflammation triggers lymphangiogenesis but may negatively impact the immune-function of lymphatic vessels, namely fluid drainage and dendritic cell (DC) migration to draining lymph nodes (dLNs). On the other hand, haptens have been shown to exert immune-stimulatory activity by inducing DC maturation. In this study we investigated how the presence of pre-established CHS-induced skin inflammation affects the induction of adaptive immunity in dLNs. Using a mouse model of oxazolone-induced skin inflammation we observed that lymphatic drainage was reduced and DC migration from skin to dLNs was partially compromised. At the same time, a significantly stronger adaptive immune response towards ovalbumin (OVA) was induced when immunization had occurred in CHS-inflamed skin as compared to uninflamed control skin. In fact, immunization with sterile OVA in CHS-inflamed skin evoked a delayed-type hypersensitivity (DTH) response comparable to the one induced by conventional immunization with OVA and adjuvant in uninflamed skin. Striking phenotypic and functional differences were observed when comparing DCs from LNs draining uninflamed or CHS-inflamed skin. DCs from LNs draining CHS-inflamed skin expressed higher levels of co-stimulatory molecules and MHC molecules, produced higher levels of the interleukin-12/23 p40 subunit (IL-12/23-p40) and more potently induced T cell activation in vitro. Immunization experiments revealed that blockade of IL-12/23-p40 during the priming phase partially reverted the CHS-induced enhancement of the adaptive immune response. Collectively, our findings indicate that CHS-induced skin inflammation generates an overall immune-stimulatory milieu, which outweighs the potentially suppressive effect of reduced lymphatic vessel function.PLoS ONE 06/2014; 9(6):e99297. · 3.53 Impact Factor