Decreased Numbers of Blood Dendritic Cells and Defective Function of Regulatory T Cells in Antineutrophil Cytoplasmic Antibody-Associated Vasculitis

BACKGROUND: Dendritic cells (DC) and regulatory cells (Treg) play pivotal roles in controlling both normal and autoimmune adaptive immune responses. DC are the main antigen-presenting cells to T cells, and they also control Treg functions. In this study, we examined the frequency and phenotype of DC subsets, and the frequency and function of Treg from patients with ANCA-associated vasculitis (AAV). METHODOLOGY/PRINCIPAL FINDINGS: Blood samples from 19 untreated patients with AAV during flares and before any immunosuppressive treatment were analyzed, along with 15 AAV patients in remission and 18 age-matched healthy controls. DC and Treg numbers, and phenotypes were assessed by flow cytometry, and in vitro suppressive function of Treg was determined by co-culture assay. When compared to healthy volunteers, absolute numbers of conventional and plasmacytoid DC were decreased in AAV patients. During the acute phase this decrease was significantly more pronounced and was associated with an increased DC expression of CD62L. Absolute numbers of Treg (CD4(+)CD25(high)CD127(low/-) Tcells) were moderately decreased in patients. FOXP3 and CD39 were expressed at similar levels on Treg from patients as compared to controls. The suppressive function of Treg from AAV patients was dramatically decreased as compared to controls, and this defect was more pronounced during flares than remission. This Treg functional deficiency occurred in the absence of obvious Th17 deviation. CONCLUSION: In conclusion, these data show that AAV flares are associated with both a decrease number and altered phenotype of circulating DC and point to a role for Treg functional deficiency in the pathogenesis of AAV

Etude du phénotype et de la fonction des cellules régulatrices T CD4+CD25+ dans le sang de patients tolérant spontanément une greffe de rein

Un des objectifs en transplantation est d induire un état de tolérance opérationnelle. Cet état, rare en transplantation rénale, se définit comme l acceptation à long terme d un greffon à fonction stable sans immunosuppresseur chez un hôte immunocompétent. Ce travail vise à comprendre les mécanismes impliqués dans le processus de tolérance opérationnelle chez les transplantés rénaux. L étude d une petite cohorte de patients tolérants a permis d identifier un phénotype particulier de leurs lymphocytes T sanguins CD4+CD25+, différent de celui des patients en rejet chronique. Nous avons montré que les patients tolérants présentent un nombre plus important de cellules CD4+CD25+FOXP3+ que les patients en rejet chronique et semblable à celui des individus sains. Ces cellules présentent également une fonction régulatrice semblable à celle d individus normaux et significativement supérieure à celle de patient en rejet chronique.Despite being efficient in preventing acute rejection, immunosuppressors have little effect on chronic rejection. A major goal in transplantation is therefore to induce a state of operational tolerance. This state, which is rare in kidney transplant recipients, is defined as long-term graft acceptance with a stable function, without immunosuppression in an immunocompetent recipient. Here we tried to understand the mechanisms implicated in operational tolerance to kidney transplants. The study of a small cohort of tolerant patients allowed us to identify a particular phenotypic profile of CD4+CD25+ blood lymphocytes that was different to that of patients with chronic rejection. Tolerant patients displayed an increased number of CD4+CD25+FOXP3+ T cells compared to patients with chronic rejection. These cells also displayed a regulatory function similar to that of healthy individuals and significantly higher than that of patients with chronic rejection.NANTES-BU Médecine pharmacie (441092101) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Altered innate functions of myeloid dendritic cells in ANCA-associated vasculitis

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Human blood mDC subsets exhibit distinct TLR repertoire and responsiveness

International audienceHuman blood DCs encompass pDCs and two subsets of mDCs: CD1c(+) mDCs and CD141(+) mDCs. The rare CD141(+) DC population is thought to be the equivalent of mouse CD8α(+) cDCs that play a significant role in antigen cross-presentation. Here, we analyzed by Q-PCR TLR1-10 expression in blood DC subsets. Whereas CD1c(+) DCs express all TLR except TLR9, CD141(+) DCs present a more restricted pattern with high expression of TLR3 and -10, expression of TLR1,-2, -6, and -8, and lack of TLR4, -5, -7, and -9. The in vitro analysis of isolated mDC subset reponsiveness to an extensive panel of TLR ligands confirmed these results, with CD141(+) DCs responding only to TLR1/2, -3, and -7/8. The cytokine/chemokine production profile of isolated CD141(+) DCs was also more restricted, as they produced mainly proinflammatory cytokines but no IL-12 and to a lower level, in comparison with CD1c(+) DCs, except for CXCL10, CCL5, and IFN-β. In contrast, with the use of a whole blood assay, we found that CD141(+) DCs produce IL-12 in response to TLR1/2, -3, and more surprisingly, -9. Finally, both mDC subsets are potent inducers of Th1 response, particularly after TLR3 triggering. Taken together, these data confirmed functional differences between blood mDC subsets. The major response of CD141(+) mDCs to TLR3 ligand and their cytokine production pattern suggest a role for these cells in antiviral immunity

HLA-DR expression in neonates after cardiac surgery under cardiopulmonary bypass: a pilot study

Abstract Monocyte HLA-DR expression has been reported as a marker of immunosuppression and a predictor of sepsis development. However, to date, there is no report on monocyte HLA-DR monitoring exclusively in neonates (< 28 days of life) who underwent cardiac surgery under cardiopulmonary bypass (CPB), which have a high risk of nosocomial infection. In this pilot study, we studied nine neonates with a diagnosis of congenital heart disease requiring surgery under CPB. There was a significant reduction in monocyte HLA-DR expression for the first two postoperative days, as compared to preoperatively (p = 0.004). Moreover, neonates who displayed an episode of NI had a dramatically lower HLA-DR expression at day 4, as compared to neonates without NI (4257 AB/c [2220–5895] vs 14,947 AB/c [9858–16,960]; p = 0.04). Our preliminary results could indicate that HLA-DR expression may be a useful biomarker of immunosuppression-induced secondary infection after CPB in neonates

Receptor activating NF-κB ligand (RANKL) is a constitutive intracellular protein in resting human basophils and is strongly induced on their surface by interleukin 3

International audienceReceptor activating NF-B ligand (RANKL) is a member of the TNF superfamily that plays a pivotal role in bone homeostasis as being the major osteoclastogenesis factor. RANKL also has pleiotropic effects in the immune system in which it is expressed by activated T and B cells and some innate lymphoid cells. RANKL-RANK interactions mediate lymph node organogenesis and immunoregulatory functions in autoimmune disease and carcinogenesis as well as cross talk between the immune system and bone. In this study, we show that basophils were the strongest RANKL mRNA-expressing cells amongst major leukocyte subsets in human blood. RANKL was preformed as an intracellular protein in resting basophils and was rapidly and strongly expressed on their surface upon stimulation with IL-3, but not other stimuli. This expression was stable for at least 6 days. Activated basophils could also release soluble RANKL in small quantities upon interaction with DCs or monocytes. In the blood, basophils were the sole cells to express membrane RANKL in response to IL-3. This study indicates that basophils should be considered as new players in the pleiotropic and complex RANKL-RANK interaction system and suggests a role for RANKL in the interaction between basophils and immune cells in inflammatory allergic tissues and secondary lymphoid organs

Persistent deficiency of circulating mucosal-associated invariant T (MAIT) cells in ANCA-associated vasculitis

International audienceObjective: Mucosal associated invariant T cells (MAIT) and innate lymphoid cells (ILCs) have immuno-regulatory functions at mucosal sites and have been involved in various inflammatory and autoimmune diseases. The aim of this study was to assess their frequencies in blood in ANCA-associated vasculitis (AAV).Methods: The frequencies and function of MAIT cells, ILCs, gdT, iNKT, NK cells were analyzed by flow cytometry on PBMC of patients with granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) without any treatment, in acute (AP) and remission phase (RP) and compared with healthy controls (HC).Results: The frequencies of MAIT cells were strongly decreased in GPA and MPA in AP compared to HC, both in never treated and in relapsing patients and independently of patient age. This was associated with an activated phenotype of patient MAIT cells, as shown by increased expression of CD69 and IFNg. MAIT cells remained decreased during RP in AAV patients. The frequencies of iNKT and gdT cells were unaffected compared to HC, whereas those of NK cells were slightly reduced during AP in MPA. We also observed a significant decrease in frequencies of total ILCs with decreased ILC2 and ILC3 and increased ILC1 during AP in both GPA and MPA compared to HC. These frequencies normalized during RP. Interestingly , we observed a significant correlation between the frequency of total ILCs and BVAS.Conclusion: We show for the first time that AAV are associated with a major decrease and an activated phenotype of blood MAIT cell. These features persisted during remission suggesting a role for MAIT cells in the pathogenesis of AAV

Phenotypically and functionally distinct CD8+ lymphocyte populations in long-term drug-free tolerance and chronic rejection in human kidney graft recipients

A substantial proportion of long-term kidney graft recipients, including those with a stable renal function in the absence of immunosuppressive therapy, present a skewed T cell receptor (TCR) Vbeta chain usage, essentially in the CD8+ subset. This study analyzed in more detail phenotypical and functional alterations of CD8+ lymphocytes in drug-free tolerant patients (DF-Tol) compared with recipients with chronic rejection (CR). Phenotyping revealed a significant increase in central memory and a decrease in effector CD8+ lymphocytes in DF-Tol versus CR. The expression of CD28+ and CD27+ on these effector cells was significantly decreased in CR. These profiles were stable over time and independent of treatment. Functionally, the CD8+CD28- lymphocytes were less sensitive to apoptosis than their CD8+CD28+ counterparts, without differences in polyclonal proliferation. The CD8+CD28- cells did not express GITR and FoxP3 but were characterized by high levels of preformed perforin and granzyme A, pointing toward a cytotoxic rather than a suppressor function. CD8+CD28- lymphocytes did not show antigen-specific degranulation when co-cultured with targets that bear donor HLA class I antigens, suggesting that the cytotoxicity is directed either to other determinants of the graft or to nongraft epitopes. Of interest, CD8+ cells from DF-Tol displayed the same profile as healthy individuals, indicating an increase in CD8+CD28- effector lymphocytes in CR rather than a decrease in DF-Tol. CD8+ lymphocytes from stable kidney recipients under conventional maintenance immunosuppression displayed a mixed profile, independent of treatment and time of sampling. Taken collectively, these data show a strong cytotoxicity-associated CD8+CD28- signature in CR and suggest a suppression of pathologic cytotoxicity in DF-Tol. Further prospective studies should assess whether serial CD8+ phenotyping may help to identify patients who are at risk for CR when immunosuppression is tapere