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International audience; Obesity is associated with low-grade chronic inflammation. Indeed, adipose tissues (AT) in obese individuals are the former site of progressive infiltration by pro-inflammatory immune cells, which together with increased inflammatory adipokine secretion induce adipocyte insulin resistance. IL-17-producing T (Th17) cells are part of obese AT infiltrating cells, and are likely to be promoted by adipose tissue-derived mesenchymal stem cells, as previously reported by our team. Whereas Th17 cell are physiologically implicated in the neutralization of fungal and bacterial pathogens through activation of neutrophils, they may also play a pivotal role in the onset and/or progression of chronic inflammatory diseases, or cancer, in which obesity is recognized as a risk factor. In this review, we will highlight the pathogenic role of IL-17A producing cells in the mechanisms leading to inflammation in obesity and to progression of obesity-related inflammatory diseases.

International audience

International audience; Recently, we have reported that adipose tissue-derived stem cells (ASC) harvested from obese donors induce a pro-inflammatory environment when co-cultured with peripheral blood mononuclear cells (MNC), with a polarization of T cells toward the Th17 cell lineage, increased secretion of IL-1beta and IL-6 pro-inflammatory cytokines, and down-regulation of Th1 cytokines, such as IFNgamma and TNFalpha. However, whether differentiated adipocytes, like the aforementioned ASC, are pro-inflammatory in obese subject AT remained to be investigated. Herein, we isolated ASC from AT of obese donors and differentiated them into adipocytes, for either 8 or 14 d. We analyzed their capacity to activate blood MNC after stimulation with phytohemagglutinin A (PHA), or not, in co-culture assays. Our results showed that co-cultures of MNC with adipocytes, like with ASC, increased IL-17A, IL-1beta, and IL-6 pro-inflammatory cytokine secretion. Moreover, like ASC, adipocytes down-regulated TNFalpha secretion by Th1 cells. As adipocytes differentiated from ASC of lean donors also promoted IL-17A secretion by MNC, an experimental model of high-fat versus chow diet mice was used and supported that adipocytes from obese, but not lean AT, are able to mediate IL-17A secretion by PHA-activated MNCs. In conclusion, our results suggest that, as ASC, adipocytes in obese AT might contribute to the establishment of a low-grade chronic inflammation state.

Objectives: Rheumatoid arthritis (RA) is characterized by defective bone repair and excessive destruction and ankylosing spondylitis (AS) by increased ectopic bone formation with syndesmophytes. Since TNF-α and IL-17A are involved in both diseases, this study investigated their effects on the osteogenic differentiation of isolated human bone marrow-derived mesenchymal stem cells (hMSCs). Methods: Differentiation of hMSCs into osteoblasts was induced in the presence or absence of IL-17A and/or TNF-α. Matrix mineralization (MM) was evaluated by alizarin red staining and alkaline phosphatase (ALP) activity. mRNA expression was measured by qRT-PCR for bone morphogenetic protein (BMP)-2 and Runx2, genes associated with osteogenesis, DKK-1, a negative regulator of osteogenesis, Schnurri-3 and receptor activator of nuclear factor kappa B ligand (RANKL), associated with the cross talk with osteoclasts, and TNF-α receptor type I and TNF-α receptor type II (TNFRII). Results: TNF-α alone increased both MM and ALP activity. IL-17A alone increased ALP but not MM. Their combination was more potent. TNF-α alone increased BMP2 mRNA expression at 6 and 12 h. These levels decreased in combination with IL-17A at 6 h only. DKK-1 mRNA expression was inhibited by TNF-α and IL-17A either alone or combined. Supporting an imbalance toward osteoblastogenesis, RANKL expression was inhibited by TNF-α and IL-17A. However, TNF-α but not IL-17 alone decreased Runx2 mRNA expression at 6 h. In parallel, TNF-α but not IL-17 alone increased Schnurri-3 expression with a synergistic effect with their combination. This may be related to an increase of TNFRII overexpression. Conclusion: IL-17 increased the effects of TNF-α on bone matrix formation by hMSCs. However, IL-17 decreased the TNF-α-induced BMP2 inhibition. Synergistic interactions between TNF-α and IL-17 were seen for RANKL inhibition and Schnurri-3 induction. Such increase of Schnurri-3 may in turn activate osteoclasts leading to bone destruction as in RA. Conversely, in the absence of osteoclasts, this could promote ectopic bone formation as in AS.

Minor histocompatibility (H) Ags are classically described as self-peptides derived from intracellular proteins that are expressed at the cell surface by MHC class I and class II molecules and that induce T cell alloresponses. We have isolated three different T cell populations from a skin biopsy of a patient suffering from acute graft-versus-host disease following sex-mismatched HLA-identical bone marrow transplantation. The first population was: 1) CD4+/CD8+ double-positive; 2) specific for an HLA class I–restricted autosomal Ag; 3) expressed a Tr1 profile with high levels of IL-10, but low IL-2 and IFN-γ; and 4) exerted regulatory function in the presence of recipient APCs. The second was CD8 positive, specific for an HLA class I–restricted autosomally encoded minor H Ag, but was only weakly cytotoxic. The third was CD4 single positive, specific for an HLA-DR7–restricted HY epitope and exerted both proliferative and cytotoxic functions. Identification of the peptide recognized by these latter cells revealed a new human HY epitope, TGKIINFIKFDTGNL, encoded by RPS4Y and restricted by HLA-DR7. In this paper, we show human CD4/CD8 double-positive, acute graft-versus-host disease–protective, minor H Ag–specific regulatory T cells and identify a novel HLA-DR7/ HY T cell epitope, encoded by RPS4Y, a potential new therapeutic target.

Objective Th17 cells have been implicated in rheumatoid arthritis (RA). We hypothesized that the interaction of T cells with bone marrow–derived mesenchymal stem cells (BM-MSCs) or with fibroblast- like synoviocytes (FLS) might, with the help of T cell–secreted inflammatory cytokines (i.e., interleukin-17A [IL-17A], tumor necrosis factor α [TNFα], and/or interferon-γ [IFNγ]), promote Th17 cell expansion and activation. Methods Peripheral blood mononuclear cells (PBMCs) from healthy blood donors were cocultured with BM-MSCs or FLS from RA patients or osteoarthritis (OA) patients. Cocultures were exposed to phytohemagglutinin with or without IL-17A, TNFα, or IFNγ. Quantitative reverse transcription–polymerase chain reaction analysis, enzyme-linked immunosorbent assay, and cytofluorometry were used to measure IL-17A production. Results Interaction of PBMCs with BM-MSCs inhibited Th1 and Th2 responses, but promoted Th17 cell expansion, as early as 24 hours, as demonstrated by increases in retinoic acid receptor–related orphan nuclear receptor γ or IL-17A messenger RNA (mRNA) levels, IL-17A secretion levels, and IL-17A–secreting cell frequency, as well as by T cell switching to the Th17 pathway after 2 rounds of stimulation with MSCs. IL-17A production was also increased in PBMCs stimulated with anti-CD3 plus anti-CD28 or in isolated CD3+ or CD45RO+ T cells, thus demonstrating the role of T cell activation. Levels of mRNA for IL-6, IL-8, and IL-1β were further amplified when T cell–secreted inflammatory cytokines were added. Interestingly, OA FLS or RA FLS also enhanced IL-17A and IL-6 production, but only RA FLS enhanced IFNγ and IL-1β production. We further demonstrated that MSC-mediated Th17 promotion requires caspase 1 activation by using an inhibitory peptide and measuring its activity. Conclusion We found that the interaction of MSCs or FLS with T cells promotes the activation and expansion of Th17 cells through caspase 1 activation. Since proinflammatory and T cell–secreted inflammatory cytokines are also amplified, this mechanism may participate in the chronicity of RA.

Objective To investigate the production of type I interferon (IFN) by myoblasts and to identify its cell source and the link to Toll-like receptor (TLR) and C-type lectin receptor (CLR) expression and function in myositis biopsy sections. Methods Production of IFNβ was assessed in cultured myoblasts after stimulation with the TLR-3 agonist poly(I-C) or with cytokines involved in Th1 and Th17 differentiation. Expression of HLA class I molecules by myoblasts was analyzed by fluorescence-activated cell sorting after activation of TLR-3 and IFNβ neutralization. In muscle biopsy samples from patients with polymyositis or dermatomyositis, expression of IFNβ, CD56 (a marker of immature muscle precursors), and HLA class I was analyzed using immunohistochemistry. Inflammatory infiltrates were characterized for the expression of myeloid dendritic cells (DCs), their associated CLRs, and the products of activated DCs, interleukin-12 (IL-12), and IL-23. Results In cultured myoblasts, stimulation of TLR-3 induced the production of IFNβ when combined with IFNγ and up-regulated the expression of HLA class I molecules, which was decreased after IFNβ blockade. In myositis biopsy tissues, immature muscle precursors overexpressing HLA class I were identified as a source of IFNβ. CLRs associated with myeloid DCs were broadly expressed in inflammatory infiltrates, in association with IL-12 and IL-23, and with immature muscle precursors. Conclusion Immature muscle precursors may represent a local source of IFNβ and the target of an immune response involving activated DCs associated with the expression of CLRs and of IL-12 and IL-23, which are implicated in T cell polarization. In turn, such local production of IFNβ after TLR-3 activation in the presence of the Th1 cytokine IFNγ may explain HLA class I overexpression in myositis.

Arterial allograft represents a material of choice for primary arterial revascularization in liver transplantation (LT) when interposition of a vascular conduit is required. In case of non-availability of such graft, the use of cryopreserved vessels should be an interesting option. Three patients were grafted using a cryopreserved iliac artery allograft (CIAA) previously harvested and stored at -140°C in a tissue bank. An auxiliary partial LT was performed in one patient for acute liver failure. During follow-up, an efficient regeneration of the native hemi-liver was observed while atrophy of the auxiliary graft occurred, leading to functional portal vein and hepatic artery thrombosis at six and nine months, respectively. Two other patients presented with celiac trunk compression because of arcuate ligament without available arterial allograft in the donor. Late arterial thrombosis occurred at six months in one patient without impairment of graft function. The last patient was alive and symptom free 29 months after LT with a patent cryopreserved arterial conduit. Our preliminary results suggest that CIAA might represent an efficient solution as vessel interposition for primary arterial hepatic revascularization in LT setting when no other suitable graft is available. However, long-term patency of CIAA remains questionable.

Taking advantage of the wide tropism of baculoviruses (BVs), we constructed a recombinant BV (BVCAR) pseudotyped with human coxsackie B-adenovirus receptor (CAR), the high-affinity attachment receptor for adenovirus type 5 (Ad5), and used the strategy of piggybacking Ad5-green fluorescent protein (Ad5GFP) vector on BVCARto transduce various cells refractory to Ad5 infection. We found that transduction of all cells tested, including human primary cells and cancer cell lines, was significantly improved using the BVCAR-Ad5GFP biviral complex compared to that obtained with Ad5GFP or BVCARGFP alone. We determined the optimal conditions for the formation of the complex and found that a high level of BVCAR-Ad5GFP-mediated transduction occurred at relatively low adenovirus vector doses, compared with transduction by Ad5GFP alone. The increase in transduction was dependent on the direct coupling of BVCARto Ad5GFP via CAR-fiber knob interaction, and the cell attachment of the BVCAR-Ad5GFP complex was mediated by the baculoviral envelope glycoprotein gp64. Analysis of the virus-cell binding reaction indicated that the presence of BVCARin the complex provided kinetic benefits to Ad5GFP compared to the effects with Ad5GFP alone. The endocytic pathway of BVCAR-Ad5GFP did not require Ad5 penton base RGD-integrin interaction. Biodistribution of BVCAR-Ad5Luc complex in vivo was studied by intravenous administration to nude BALB/c mice and compared to Ad5Luc injected alone. No significant difference in viscerotropism was found between the two inocula, and the liver remained the preferred localization. In vitro, coagulation factor X drastically increased the Ad5GFP-mediated transduction of CAR-negative cells but had no effect on the efficiency of transduction by the BVCAR-Ad5GFP complex. Various situations in vitro or ex vivo in which our BVCAR-Ad5 duo could be advantageously used as gene transfer biviral vector are discussed.

We have previously reported that alloreaction can lead to activation of dendritic cells through secretion of inflammatory cytokines. Here, we addressed whether alloreaction-derived cytokines may also lead to acute myelogenous leukemia (AML) blast differentiation. With this aim, supernatant (sn) harvested from major or minor histocompatibility antigen-mismatched mixed lymphocyte reaction (MLR) were used to culture French American Bristish (FAB) type M4 or M5 AML blasts. Our results showed that the secreted factors induced upregulation of CD40, CD54, and/or HLA molecules in AML blasts. Protein fractionation, blockade experiments and exogenous cytokine reconstitution demonstrated the involvement of TNF in the upregulation of CD54, CD40 and HLA-class II molecules, and of IFNgamma in the increase of HLA-class I and class II molecule expression. But, in line of its much higher levels of secretion, TNFbeta, rather than TNFalpha, was likely to play a preponderant role in AML blast differentiation. Moreover TNFbeta and IFNgamma were also likely to be involved in the AML blast differentiation-mediated by HLA-identical donor T-cell alloresponse against recipient AML blasts. In conclusion, we show herein that upon allogeneic reaction, TNFbeta secretion contributes, in concert with IFNgamma, to increase or restore surface molecules involved in AML blast interaction with T cells.

The first successful human hand transplantation, performed on September 1998, has translated the scope of 'composite tissue allotransplantation' from research concepts into clinical practice. Beyond microsurgical problems that have been overcome several years ago, the main obstacle that still prevents the generalization of composite tissue allotransplantation is immunologic. This review, which summarizes the evidence obtained both from experimental animal models and from the first recipients of a hand transplant, is focused on the two immunological characteristics of composite allografts that set them apart from other solid organ allografts: (i) they contain skin tissue that elicits a strong immune response; and (ii) they contain lymphoid tissues (such as bone marrow and lymph nodes) that have the potential both to attack the recipient, and also to down-modulate the host immune response and induce tolerance. While on one hand, the composite tissue allografts raise new challenges to transplant immunologists, on the other they provide answers to questions that have remained unresolved for a long time. In this sense, composite tissue allografts extend a helping hand to transplant immunologists.

Ex vivo expansion of hematopoietic stem cells (HSC) can help reduce cytopenia following transplantation, especially in NHL patients whose BM is deficient because of extensive chemotherapy. We have previously reported that human umbilical vein endothelial cells (HUVEC) can contribute to improved PBPC expansion when used in co-culture with CD34(+) cells.We evaluated the roles of direct HUVEC CD34(+) contact and HUVEC-produced soluble factors. We cultured CD34(+) PBPC harvested from NHL patients in four different conditions: (1) liquid culture without HUVEC; (2) co-culture in contact with HUVEC; (3) co-culture with HUVEC but without direct contact; (4) liquid culture with HUVEC-conditioned medium (CM). Thrombopoietin (Tpo), Flk2Flt3 ligand (FL) and c-kit ligand (KL) with or without rhIL-6 were added to these four culture conditions.Our results showed that HUVEC co-culture or addition of HUVEC-CM to Tpo, FL and KL (TFK) improved CD34(+) PBPC expansion compared with liquid culture, as determined by total viable nucleated cells (TNC), colony-forming cell assay (CFC) and week-6 cobblestone area-forming cells (Wk-6 CAFC) expansions. Non-contact culture led to similar PBPC expansion as contact co-culture; moreover, HUVEC-CM improved PBPC expansion. However, when rhIL-6 was added to HUVEC-CM with TFK, no significant difference was observed. Finally, high quantities of IL-6 were detected in HUVEC-CM and addition of anti-IL-6 Ab inhibited the positive effect of HUVEC on PBPC expansion. Our results thus suggest that HUVEC may improve PBPC expansion, at least through IL-6 secretion.

International audience; BACKGROUND: A bilateral hand allotransplantation was performed in a patient six years ago. Whereas skin is known to be highly immunogenic, grafts have been well accepted up to now. Therefore, here we investigated the putative presence of regulatory T cells in the graft. METHODS: Skin biopsies were performed at different time points and analyzed by immunochemistry. T cells were initially expanded with interleukin (IL)-2. In the latter biopsy, skin was directly analyzed by reverse-transcriptase polymerase chain reaction without any culture. RESULTS: When tested against donor mononuclear cells, donor-primed skin T cells demonstrated unresponsiveness and inhibited donor-directed blood T cell alloresponse. Moreover, their T-cell receptor-Vbeta repertoire was skewed, in contrast to that of peripheral blood T cells. Retrospectively, nuclear FoxP3 expression in skin was measured by immunohistochemistry and was found positive at that time, but appeared to increase with time. This result was supported by the measurement of FoxP3 messenger RNA (mRNA) expression in the latter fresh biopsy, which showed higher levels than that of blood, together with no expression of perforin mRNA, but increased expression of transforming growth factor-beta and IL-10. No FoxP3 mRNA expression was found in the contralateral leg, due to the absence of T cell infiltrate. CONCLUSION: This study shows the presence of the FoxP3 marker, in a well accepted human composite tissue allograft, up to six years posttransplantation. Because a suppressive cytokinic profile was also detected intragraft, in the absence of perforin mRNA expression, our data suggest that regulatory T cells could play a role in the long-term survival of this allograft.

Here, we investigated the influence of cyclosporin A (CsA) on dendritic cell (DC) generation. With this aim, human DC were propagated from monocytes in serum-free medium with granulocyte macrophage-colony stimulating factor and interleukin-4. DC were then exposed to tumor necrosis factor alpha (TNF-alpha) for maturation. Our results show that CsA does not impair commitment of monocytes into DC, as assessed by loss of CD14 and increase of CD40 and CD1a. However, TNF-alpha-induced DC maturation was affected, as CsA-treated DC expressed lower levels of human leukocyte antigen and costimulatory molecules but sustained levels of CD1a, and less DC expressed DC-lysosomal-associated-membrane-protein (LAMP) and CD83. Accordingly, CsA inhibited the allostimulatory and accessory cell functions of DC. Surprisingly, when other maturation stimuli were used, we observed that CsA significantly inhibited maturation induced by lipopolysaccharides but not by polyribocytidylic acid or CD40 ligand, as assessed by DC phenotype and functions. Therefore, our results indicate that CsA may differentially affect DC maturation.

TRACHEAL reconstruction after extensive resection remains an unsolved surgical problem. Several methods of substitution have been tested including prosthetic material or autologous tissue, but none of them replaced the native trachea adequately. Recent studies indicate that cryopreserved tracheal allograft can be proposed as substitution material in animals models. The aim of this study was to document mechanical and histologic characteristics of human trachea (HT) before and after cryopreservation using different cryoprotectants.

International audience; We recently demonstrated that dendritic cells (DCs) can be generated from monocytes in the presence of high concentrations of human serum (HS), provided the extra-cellular pH is maintained at plasma values. Because monocyte-derived DCs (Mo-DCs) can also be generated in the presence of fetal calf serum (FCS) or serum-free medium, we have investigated whether these different culture supplements influence DC generation. With this aim, purified monocytes were cultured with GM-CSF plus IL-4 for 6 days and were further exposed to TNF-alpha for 2 additional days, in the presence of HS, autologous plasma (AP), FCS, or X-VIVO 20, a serum-free medium. Our results show that good yields of functionally mature DCs can reproducibly be obtained in the presence of HS or AP, as assessed by CD83 and CD86 up-regulation, dextran-FITC uptake, allogeneic MLR assays and the induction of an autologous response. Interestingly, the effect of serum on DC generation was probably not only quantitative, but also qualitative, since (i) the majority of HS- or AP-cultured DCs expressed CD83 with very weak levels of CD1a, whereas CD83+ DCs cultured in FCS or X-VIVO were mostly CD1a++; (ii) HS- and AP-cultured DCs were much more granular and heterogeneous than FCS- or X-VIVO-cultured DCs, and (iii) the presence of Birbeck-like granules was preferentially observed in HS- or AP-cultured DCs, as assessed by electron microscopy. That these different cells resemble dermal DCs (DDCs) was further supported by the observations that most of the cells displayed intracytoplasmic FXIIIa in the absence of Lag antigen, and expressed E-cadherin at very low levels. Altogether, our results indicate that starting from the same monocytic population, different subsets of DCs can be generated, depending on the culture conditions. Thus, HS or AP favors the generation of fully mature DCs that resemble activated dermal DCs, whereas FCS, or X-VIVO preferentially leads to the generation of less mature CD1a++ dermal-like DCs.

International audience; By using bifunctional T cell populations, we have shown in this report that elicitation of helper versus cytolytic function depends on the stimulatory signal at the membrane. Interestingly enough, the transduction of these signals is likely to be achieved via different metabolic pathways. Thus, helper function is associated with intracellular Ca2+ mobilization and PLC activation, while cytolysis can occur even in the absence of detectable levels of these second messengers. These results indicate that selective activation through the same membrane-transducing molecule may orientate T cell function through qualitatively or quantitatively different second messengers. This would be an important part of immune regulation.

In the present study, we explored the specific requirements for lysis of human activated T cells by CD4+ CTLs. This was achieved by using human CD4+ T cell lines or clones specific for a peptidic fragment of influenza virus as both CTL effectors and target T cells (TTCs). Our results further establish that human activated T cells expressing HLA-DR molecules can present Ag to and be lysed by CD4+ HLA-DR restricted CTLs. This killing is Ag specific and HLA-DR restricted. It can be observed whether TTCs are heterologous or autologous, CD4+ or CD8+. However, we find that in our model: (a) TTCs are able to present artificially processed peptidic fragments of Ag, but not the corresponding natural Ag in the context of class II determinants, even if they can process whole virus in the context of class I determinants; (b) TTCs must express high density of HLA-DR molecules on their membrane; (c) preincubation of TTCs with high concentrations of peptide is required; and (d) interestingly enough, addition of free peptide at similar concentration during the cytolytic assay to replace TTC preincubation inhibits TTC lysis by at least two different mechanisms, i.e., cold-target inhibition in which CTLs serve as their own cold targets and inhibition at the effector cell level. From these results, one can conclude that stringent conditions are required for lysis of activated T cells by class-II-restricted CTLs.