Dendritic cells (DC) are highly specialized antigen-presenting cells characterized by the ability to prime T-cell responses. Mesenchymal stem cells (MSC) are adult stromal progenitor cells displaying immunomodulatory activities including inhibition of DC maturation in vitro. However, the specific impact of MSC on DC functions, upon in vivo administration, has never been elucidated. Here we show that murine MSC impair Toll-like receptor-4 induced activation of DC resulting in the inhibition of cytokines secretion, down-regulation of molecules involved in the migration to the lymph nodes, antigen presentation to CD4 + T cells, and cross-presentation to CD8 + T cells. These effects are associated with the inhibition of phosphorylation of intracellular mitogen-activated protein kinases. Intravenous administration of MSC decreased the number of CCR7 and CD49dβ1 expressing CFSE-labeled DC in the draining lymph nodes and hindered local antigen priming of DO11.10 ovalbumin-specific CD4 + T cells. Upon labeling of DC with technetium-99m hexamethylpropylene amine oxime to follow their in vivo biodistribution, we demonstrated that intravenous injection of MSC blocks, almost instantaneously, the migration of subcutaneously administered ovalbumin-pulsed DC to the draining lymph nodes. These findings indicate that MSC significantly affect DC ability to prime T cells in vivo because of their inability to home to the draining lymph nodes and further confirm MSC potentiality as therapy for immune-mediated diseases.immunomodulation | tolerance S tromal progenitors of mesodermal cells, referred to as mesenchymal stem cells (MSC) or multipotent mesenchymal stromal cells, are a heterogeneous population of self-renewing and multipotent cells isolated from the bone marrow (BM) (1). MSC raised hopes for their clinical exploitation for tissue-repair strategies and increasing experimental evidence supports their use also for immune-mediated diseases (2). In fact, MSC display a striking capacity of modulating the immune response (3). Despite a large body of experimental studies addressing the in vitro effects of MSC on immune cells, little is known about the mechanisms of MSCmediated inhibition of the in vivo immune response. Dendritic cells (DC) are unique antigen-presenting cells (APCs) endowed with the ability of acquiring and processing antigens, up-regulating costimulatory molecules and therefore priming naive T cells. To present antigens to naive T cells, CCR7-expressing DC must migrate through lymphatic vessels from sites of inflammation to the closest draining lymph node (4). Activation of DC via Toll-like receptors (TLRs) up-regulates the expression of chemokine receptors involved in DC migration to the lymph nodes and enhances their in vivo mobilization properties (5). As a consequence, the total number of DC migrating in the draining lymph nodes deeply affects naive T-cell priming (6). Here we show that murine MSC inhibit in vitro DC effector properties, including antigen processing and presentation to T cells through the inhib...

Mutations resulting in charge reversal in the y-domain of PSTPIP1 (E→K) and increased interaction with pyrin cause a distinct autoinflammatory disorder defined by clinical and biochemical features not found in patients with PAPA syndrome, indicating a unique genotype-phenotype correlation for mutations in the PSTPIP1 gene. This is the first inborn autoinflammatory syndrome in which inflammation is driven by uncontrolled release of members of the alarmin family.

ObjectiveNLRP12 mutations have been described in patients affected with peculiar autoinflammatory symptoms. This study was undertaken to characterize NLRP12 mutations in patients with autoinflammatory syndromes, particularly a novel missense mutation, p.D294E, affecting a protein sequence crucial for ATP binding, which was identified in a Caucasian family with familial cold-induced autoinflammatory syndrome in some family members.MethodsFifty patients were tested for NLRP12 mutations. A Caucasian family with the p.D294E missense mutation of NLRP12 in some family members was clinically characterized. In vitro analysis of the effects of the mutation on NF-κB activity was performed in HEK 293 cells after cotransfection of the cells with a luciferase NF-κB–responsive element and mutant or wild-type (WT) NLRP12 expression plasmids. NF-κB activity was also evaluated 24 hours after stimulation with tumor necrosis factor α in monocytes from individual family members carrying the mutation. Furthermore, secretion of interleukin-1β (IL-1β), production of reactive oxygen species (ROS), and activation of antioxidant systems in patient and healthy donor monocytes, under resting conditions and after stimulation with pathogen-associated molecular patterns (PAMPs), were also assessed.ResultsIn the family assessed, the p.D294E mutation segregated in association with a particular sensitivity to cold exposure (especially arthralgias and myalgia), but not always with an inflammatory phenotype (e.g., urticarial rash or fever). In vitro, the mutant protein maintained the same inhibitory activity as that shown by WT NLRP12. Consistently, NLRP12-mutated monocytes showed neither increased levels of p65-induced NF-κB activity nor higher secretion of IL-1β. However, the kinetics of PAMP-induced IL-1β secretion were significantly accelerated, and high production of ROS and up-regulation of antioxidant systems were demonstrated.ConclusionEven with a variable range of associated manifestations, the extreme sensitivity to cold represents the main clinical hallmark in an individual carrying the p.D294E mutation of the NLRP12 gene. Although regulation of NF-κB activity is not affected in patients, redox alterations and accelerated secretion of IL-1β are associated with this mild autoinflammatory phenotype.

Recent studies suggested that human CD56brightCD16− NK cells may play a role in the regulation of the immune response. Since the mechanism(s) involved have not yet been elucidated, in the present study we have investigated the role of nucleotide-metabolizing enzymes that regulate the extracellular balance of nucleotides/nucleosides and produce the immunosuppressive molecule adenosine (ADO). Peripheral blood CD56dimCD16+ and CD56brightCD16− NK cells expressed similar levels of CD38. CD39, CD73, and CD157 expression was higher in CD56brightCD16− than in CD56dimCD16+ NK cells. CD57 was mostly expressed by CD56dimCD16+ NK cells. CD203a/PC-1 expression was restricted to CD56brightCD16− NK cells. CD56brightCD16− NK cells produce ADO and inhibit autologous CD4+ T cell proliferation. Such inhibition was 1) reverted pretreating CD56brightCD16− NK cells with a CD38 inhibitor and 2) increased pretreating CD56brightCD16− NK cells with a nucleoside transporter inhibitor, which increase extracellular ADO concentration. CD56brightCD16− NK cells isolated from the synovial fluid of juvenile idiopathic arthritis patients failed to inhibit autologous CD4+ T cell proliferation. Such functional impairment could be related to 1) the observed reduced CD38/CD73 expression, 2) a peculiar ADO production kinetics, and 3) a different expression of ADO receptors. In contrast, CD56brightCD16− NK cells isolated from inflammatory pleural effusions display a potent regulatory activity. In conclusion, CD56brightCD16− NK cells act as “regulatory cells” through ADO produced by an ectoenzymes network, with a pivotal role of CD38. This function may be relevant for the modulation of the immune response in physiological and pathological conditions, and it could be impaired during autoimmune/inflammatory diseases.