The trial showed that low-dose interleukin-2 was not associated with adverse effects and led to Treg recovery and concomitant clinical improvement in patients with HCV-induced vasculitis, an autoimmune condition. (Funded by the French Agency for Research on AIDS and Viral Hepatitis [ANRS] and others; ClinicalTrials.gov number, NCT00574652.).

Rationale: Microvesicles (MVs) are anuclear fragments of cells released from the endosomal compartment or shed from surface membranes. We and other investigators demonstrated that MVs released by mesenchymal stem cells (MSCs) were as effective as the cells themselves in inflammatory injuries, such as after endotoxininduced acute lung injury. However, the therapeutic effects of MVs in an infectious model of acute lung injury remain unknown.Objectives: We investigated the effects of human MSC MVs on lung inflammation, protein permeability, bacterial clearance, and survival after severe bacterial pneumonia.Methods: We tested the effects of MVs derived from human MSCs on Escherichia coli pneumonia in mice. We also studied the interactions between MVs and human monocytes and human alveolar epithelial type 2 cells.Measurements and Main Results: Administration of MVs derived from human MSCs improved survival in part through keratinocyte growth factor secretion and decreased the influx of inflammatory cells, cytokines, protein, and bacteria in mice injured with bacterial pneumonia. In primary cultures of human monocytes or alveolar type 2 cells, the uptake of MVs was mediated by CD44 receptors, which were essential for the therapeutic effects. MVs enhanced monocyte phagocytosis of bacteria while decreasing inflammatory cytokine secretion and increased intracellular ATP levels in injured alveolar epithelial type 2 cells. Prestimulation of MSCs with a toll-like receptor 3 agonist further enhanced the therapeutic effects of the released MVs.Conclusions: MVs derived from human MSCs were as effective as the parent stem cells in severe bacterial pneumonia.

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Since either macrophages (Mphi) or dendritic cells (DC) differentiate from monocytes (MO) depending on culture conditions, we investigated the relationship of the DC and Mphi differentiation pathways. Culturing MO-enriched blood mononuclear cells with Mphi colony-stimulating factor (M-CSF) or with granulocyte/Mphi (GM)-CSF induced Mphi with a different morphology and CD14/CD1a expression. In contrast, in cultures with GM-CSF and interleukin (IL)-4, cells rapidly became nonadherent and acquired DC morphology, ultrastructure, CD1a expression, and most DC markers; they lost membrane CD14 and CD64 and capacity of phagocytosis, displayed less CD68 than Mphi, but retained nonspecific esterase activity. These DC directly developed from MO without proliferation inasmuch as only day 0 FACS-sorted MO, but not small CD14- cells, differentiated into DC when cultured with GM-CSF and IL-4, or to Mphi with M-CSF While overall cell numbers declined, DC numbers plateaued from culture day 2 onwards, indicating that most had differentiasted by then. This differentiation was radioresistant and occurred without [3H]thymidine incorporation. Commitment to differentiate into DC with GM-CSF and IL-4 was irreversible by day 2, since discontinuing IL-4 at this point did not revert cells to Mphi. Alternatively, cells rapidly converted to DC when IL-4 was added from day 2 to cultures initiated with GM-CSF only. If cultures were initiated with M-CSF and switched to GM-CSF and IL-4 after 2 or 5 days, about half of the cells still converted to DC. Thus, the capacity of MO and even of Mphi to differentiate into DC was conserved for at least this period. The increased capacity to stimulate the mixed leukocyte reaction correlated with the relative number of CD1a+ cells at any time and under each condition tested, a confirmation that these cells functionally qualify as DC. Thus, MO and even Mphi can be directed to differentiate into DC depending on the cytokine microenvironment.

ObjectiveRegulatory T cells (Tregs) prevent autoimmunity and control inflammation. Consequently, any autoimmune or inflammatory disease reveals a Treg insufficiency. As low-dose interleukin-2 (ld-IL2) expands and activates Tregs, it has a broad therapeutic potential.AimWe aimed to assess this potential and select diseases for further clinical development by cross-investigating the effects of ld-IL2 in a single clinical trial treating patients with 1 of 11 autoimmune diseases.MethodsWe performed a prospective, open-label, phase I–IIa study in 46 patients with a mild to moderate form of either rheumatoid arthritis, ankylosing spondylitis, systemic lupus erythematosus, psoriasis, Behcet’s disease, granulomatosis with polyangiitis, Takayasu’s disease, Crohn’s disease, ulcerative colitis, autoimmune hepatitis and sclerosing cholangitis. They all received ld-IL2 (1 million IU/day) for 5 days, followed by fortnightly injections for 6 months. Patients were evaluated by deep immunomonitoring and clinical evaluation.Resultsld-IL2 was well tolerated whatever the disease and the concomitant treatments. Thorough supervised and unsupervised immunomonitoring demonstrated specific Treg expansion and activation in all patients, without effector T cell activation. Indication of potential clinical efficacy was observed.ConclusionThe dose of IL-2 and treatment scheme used selectively activate and expand Tregs and are safe across different diseases and concomitant treatments. This and preliminary indications of clinical efficacy should licence the launch of phase II efficacy trial of ld-IL2 in various autoimmune and inflammatory diseases.Trial registration numberNCT01988506.

We have identified a new regulatory T cell population (CD8(+)Foxp3(+)) in colorectal tumours. After isolation from cancer tissue these CD8(+)Foxp3(+) cells demonstrated strong immunosuppressive properties in vitro. These data suggest that these cells may contribute to tumoral immune escape and disease progression.

Background Primary Sjögren's syndrome (pSS) is the autoimmune disease associated with the higher risk of developing non-Hodgkin lymphoma. Objective To determine the nature of B cells driving lymphoproliferation in pSS. Methods B cell subsets and function were analyzed in peripheral blood from 66 adult patients with pSS [including 14 patients with B-cell lymphoproliferative disorder (LPD)] and 30 healthy donors, using flow cytometry, calcium mobilization, and gene array analysis. We tested by ELISA the reactivity of recombinant antibodies isolated from single B cells from pSS-LPD. Results We report here the expansion of an unusual CD21-/low B-cell population which correlates with lymphoproliferation in pSS patients. A majority of CD21–/low B cells from pSS patients expressed autoreactive antibodies, which recognized nuclear and cytoplasmic structures. These B cells belonged to the memory compartment because their immunoglobulin genes were mutated. They were unable to induce calcium flux, become activated, or proliferate in response to B-cell receptor and/or CD40 triggering, suggesting that these autoreactive B cells may be anergic. However, CD21–/low B cells from pSS remained responsive to TLR stimulation. Gene array analyses of CD21–/low B cells revealed molecules specifically expressed in these B cells and that are likely to induce their unresponsive stage. Conclusion pSS patients who display high frequencies of autoreactive and unresponsive CD21-/low B cells are susceptible for developing lymphoproliferation. These cells remain in peripheral blood controlled by functional anergy instead of being eliminated, and chronic antigenic stimulation through TLR stimulation may create a favorable environment for breaking tolerance and activating these cells.

Most autoimmune diseases (AID) are linked to an imbalance between autoreactive effector T cells (Teffs) and regulatory T cells (Tregs). While blocking Teffs with immunosuppression has long been the only therapeutic option, activating/expanding Tregs may achieve the same objective without the toxicity of immunosuppression. We showed that low-dose interleukin-2 (ld-IL-2) safely expands/activates Tregs in patients with AID, such HCV-induced vasculitis and Type 1 Diabetes (T1D). Here we analyzed the kinetics and dose-relationship of IL-2 effects on immune responses in T1D patients. Ld-IL-2 therapy induced a dose-dependent increase in CD4(+)Foxp3(+) and CD8(+)Foxp3(+) Treg numbers and proportions, the duration of which was markedly dose-dependent. Tregs expressed enhanced levels of activation markers, including CD25, GITR, CTLA-4 and basal pSTAT5, and retained a 20-fold higher sensitivity to IL-2 than Teff and NK cells. Plasma levels of regulatory cytokines were increased in a dose-dependent manner, while cytokines linked to Teff and Th17 inflammatory cells were mostly unchanged. Global transcriptome analyses showed a dose-dependent decrease in immune response signatures. At the highest dose, Teff responses against beta-cell antigens were suppressed in all 4 patients tested. These results inform of broader changes induced by ld-IL-2 beyond direct effects on Tregs, and relevant for further development of ld-IL-2 for therapy and prevention of T1D, and other autoimmune and inflammatory diseases.