Objective: Proteasomes are targets of humoral autoimmune response in patients with connective tis... more Objective: Proteasomes are targets of humoral autoimmune response in patients with connective tissue diseases and other organ-specific autoimmune diseases. The finding of circulating proteasomes in psoriasis, the multiplicity of mechanisms regulated by proteasomes that are also implicated in the pathogenesis of psoriatic arthritis (PsA), and the increasing evidence linking PsA and autoimmunity led us to evaluate whether the 20S proteasome represents an antibody target in PsA. Methods: Serum samples from 36 patients with PsA and 30 age- and sex-matched healthy subjects were tested for the presence of anti-20S proteasome antibodies (anti-20S antibody). Additional controls included 24 patients with systemic lupus erythematosus (SLE) and 20 with rheumatoid arthritis (RA). The associations of anti-20S antibodies with clinical, laboratory, and therapeutic measures were evaluated. Results: 27.8% of the PsA patients were positive for anti-20S antibody compared to 41.6% of the SLE group and 5% of the RA group. None of the healthy subjects were seropositive for anti-20S antibody. In PsA, anti-20S seropositivity was not associated with the presence of other autoantibodies or with a particular subgroup of articular involvement. Conclusion: Immunoreactivity against proteasomes occurs frequently in patients with PsA. This finding supports the concept of PsA as an autoimmune disease and opens new avenues for investigating its pathogenesis.
OBJECTIVE-In rheumatoid arthritis (RA), telomeres of lymphoid and myeloid cells are ageinappropri... more OBJECTIVE-In rheumatoid arthritis (RA), telomeres of lymphoid and myeloid cells are ageinappropriately shortened, suggesting excessive turnover of hematopoietic precursor cells (HPC). We have examined functional competence (proliferative capacity, maintenance of telomeric reserve) of CD34 + HPC in RA. METHODS-Frequencies of peripheral blood CD34 + CD45 + HPC of 63 rheumatoid factor positive RA patients and 48 matched controls were measured by flow cytometry. Proliferative burst, cell cycle dynamics, and induction of lineage-restricted receptors were tested in purified CD34 + HPC after stimulating with early hematopoietins. Telomeric sequences were quantified by real-time PCR. HPC functions were correlated with disease duration, activity, severity, and treatment. RESULTS-In healthy donors, CD34 + HPC accounted for 0.05% of nucleated cells; their numbers were strictly age-dependent and declined at a rate of 1.3%/year. In RA patients, CD34 + HPC frequencies were age-independently reduced to 0.03%. Upon growth factor stimulation, control HPC passed through 5 replication cycles over 4 days. In contrast, RA-derived HPC completed only 3 generations. Telomeres of RA CD34 + HPC were age-inappropriately shortened by 1,600 bp. All HPC defects were independent from disease duration, disease activity, and smoking status; and were present to the same degree in untreated patients. CONCLUSIONS-In RA, circulating bone marrow-derived progenitor cells are diminished, with concentrations stagnated at levels typical for old control individuals. HPC from RA patients display growth factor non-responsiveness and sluggish cell cycle progression; marked telomere shortening indicates proliferative stress-induced senescence. Defective HPC function independent from disease activity markers suggests bone marrow failure as a potential pathogenic factor in RA.
In rheumatoid arthritis (RA), dysfunctional T cells sustain chronic inflammatory immune responses... more In rheumatoid arthritis (RA), dysfunctional T cells sustain chronic inflammatory immune responses in the synovium. Even unprimed T cells are under excessive replication pressure, suggesting an intrinsic defect in T cell regeneration. In naive CD4 CD45RA + T cells from RA patients, DNA damage load and apoptosis rates were markedly higher than in controls; repair of radiation-induced DNA breaks was blunted and delayed. DNA damage was highest in newly diagnosed untreated patients. RA T cells failed to produce sufficient transcripts and protein of the DNA repair kinase ataxia telangiectasia (AT) mutated (ATM). NBS1, RAD50, MRE11, and p53 were also repressed. ATM knockdown mimicked the biological effects characteristic for RA T cells. Conversely, ATM overexpression reconstituted DNA repair capabilities, response patterns to genotoxic stress, and production of MRE11 complex components and rescued RA T cells from apoptotic death. In conclusion, ATM deficiency in RA disrupts DNA repair and renders T cells sensitive to apoptosis. Apoptotic attrition of naive T cells imposes lymphopenia-induced proliferation, leading to premature immunosenescence and an autoimmune-biased T cell repertoire. Restoration of DNA repair mechanisms emerges as an important therapeutic target in RA.
In rheumatoid arthritis (RA), hematopoietic progenitor cells (HPC) have age-inappropriate telomer... more In rheumatoid arthritis (RA), hematopoietic progenitor cells (HPC) have age-inappropriate telomeric shortening suggesting premature senescence and possible restriction of proliferative capacity. In response to hematopoietic growth factors RA-derived CD34 + HPC expanded significantly less than age-matched controls. Cell surface receptors for stem cell factor (SCF), Flt 3-Ligand, IL-3 and IL-6 were intact in RA HPC but the cells had lower transcript levels of cell cycle genes, compatible with insufficient signal strength in the ERK pathway. Cytokine-induced phosphorylation of ERK1/2 was diminished in RA HPC whereas phosphorylated STAT3 and STAT5 molecules accumulated to a similar extent as in controls. Confocal microscopy demonstrated that the membrane-proximal colocalization of K-Ras and B-Raf were less efficient in RA-derived CD34 + cells. Thus, hyporesponsiveness of RA HPC to growth factors results from dampening of the ERK signaling pathways; with a defect localized in the very early steps of the ERK signaling cascade.
Immune responses to citrullinated neoantigens and clinical efficacy of costimulation blockade ind... more Immune responses to citrullinated neoantigens and clinical efficacy of costimulation blockade indicate a general defect in maintaining T-cell tolerance in rheumatoid arthritis (RA)3. To examine whether TCR threshold calibration contributes to disease pathogenesis, signaling in RA T cells was quantified. RA patients had a selective increase in ERK phosphorylation compared to demographically matched controls due to a mechanism distal of Ras activation. Increased ERK responses included naïve and memory CD4 and CD8 T cells and did not correlate with disease activity. The augmented ERK activity delayed SHP-1 recruitment to the TCR synapse and sustained TCR-induced ZAP70 and NF-κB signaling, facilitating responses to suboptimal stimulation. Increased responsiveness of the ERK pathway was also a characteristic finding in the SKG mouse model of RA where it preceded clinical symptoms. Treatment with subtherapeutic doses of a MEK-1/2 inhibitor delayed arthritis onset and reduced severity, suggesting that increased ERK phosphorylation predisposes for autoimmunity and can be targeted to prevent disease.
The best discrimination between the two groups was achieved by the percentage of CD27-neg. events... more The best discrimination between the two groups was achieved by the percentage of CD27-neg. events within the CD40L-positive or IFN-gamma producing cells. Using the former and a threshold of 41% of CD27-neg. events for the diagnosis of active pulmonary TB, the positive predictive value for active pulmonary TB wasN80% and sputum smearnegative but culture positive cases were correctly classified. Conclusions: This novel immunological blood test represents a diagnostic advance in the field of TB. It also identifies cases that are sputum microscopy negative, which might be of particular use in HIV or children This will have to be confirmed in future studies. The test requires only a simple flow cytometer.
RA is the prototypic chronic inflammatory disease, characterized by progressive articular cartila... more RA is the prototypic chronic inflammatory disease, characterized by progressive articular cartilage and bone destruction. The systemic nature of RA is evidenced by the increased risk of atherosclerosis and lymphoproliferative disorders. Components of both the innate and adaptive immune system are implicated in the pathophysiology of the articular and extra-articular manifestations of the disease. A fundamental process in the onset of RA is the breakdown in self-tolerance. Accelerated ageing of immune cells (immunosenescence) appears to be a major mechanism favouring the disruption of tolerance. Telomere erosion, a hallmark of immunosenescence, is present in lymphoid (naı ¨ve and memory T cells) and myeloid (granulocytes) cells in RA. The premature ageing process also involves the haematopoietic stem and progenitor cells (CD34 + HSPC), thus extending the RA immunopathogenesis to include early events in the shaping of the immune system. This review summarizes current concepts of HSPC ageing and its impact on immune regeneration, highlighting the phenotypic and functional similarities between elderly and RA HSPC.
Background-Unstable atherosclerotic plaque is characterized by an infiltrate of inflammatory cell... more Background-Unstable atherosclerotic plaque is characterized by an infiltrate of inflammatory cells. Both macrophages and T cells have been implicated in mediating the tissue injury leading to plaque rupture; however, signals regulating their activation remain unidentified. Infectious episodes have been suspected to render plaques vulnerable to rupture. We therefore explored whether plasmacytoid dendritic cells (pDCs) that specialize in sensing bacterial and viral products can regulate effector functions of plaque-residing T cells and thus connect host infection and plaque instability. Methods and Results-pDCs were identified in 53% of carotid atheromas (nϭ30) in which they localized to the shoulder region and produced the potent immunoregulatory cytokine interferon (INF)-␣. IFN-␣ transcript concentrations in atheroma tissues correlated strongly with plaque instability (PϽ0.0001). Plaque-residing pDCs responded to pathogenderived motifs, CpG-containing oligodeoxynucleotides binding to toll-like receptor 9, with enhanced IFN-␣ transcription (Pϭ0.03) and secretion (Pϭ0.007). IFN-␣ emerged as a potent regulator of T-cell function, even in the absence of antigen recognition. Specifically, IFN-␣ induced a 10-fold increase of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) on the surface of CD4 T cells (PϽ0.0001) and enabled them to effectively kill vascular smooth muscle cells (Pϭ0.0003). Conclusions-pDCs in atherosclerotic plaque sense microbial motifs and amplify cytolytic T-cell functions, thus providing a link between host-infectious episodes and acute immune-mediated complications of atherosclerosis. (Circulation.
Abnormal innate and adaptive immune responses are critically involved in the pathogenesis of rheu... more Abnormal innate and adaptive immune responses are critically involved in the pathogenesis of rheumatoid arthritis (RA). Anti-inflammatory and immunosuppressive therapies have been highly successful, but a cure for the disease has remained elusive, mostly due to lack of knowledge of disease instigators and the causative immune system abnormalities. RA is associated with premature aging of the immune system, which has been attributed to the chronic inflammatory milieu. However, recent data draw attention to processes of impaired immune regeneration as an underlying defect. Specifically, bone marrow hematopoietic stem cells (HSCs), permanently regenerating myeloid and lymphoid lineages, are functionally defective in RA, jeopardizing repopulation of the immune system. In RA, the pool of circulating HSCs is contracted and HSCs respond inadequately to hematopoietic growth factors. Most importantly, RA HSCs have age-inappropriate telomeric shortening, indicative of excessive proliferative stress. Defects in HSCs broaden the immunopathogenesis of RA to include early events in the shaping of the immune system. Restoring HSC function will be a necessary step in re-establishing immune health in RA patients. aging n DNA damage n hematopoiesis n hematopoietic stem cells n HSC n RA n rheumatoid arthritis n senescence n telomerase n telomeres
Inflammation plays a pivotal role in the initiation and progression of atherosclerosis (ATH). Due... more Inflammation plays a pivotal role in the initiation and progression of atherosclerosis (ATH). Due to their potent immunomodulatory properties, mesenchymal stromal cells (MSCs) are evaluated as therapeutic tools in ATH and other chronic inflammatory disorders. Aging reduces MSCs immunopotency potentially limiting their therapeutic utility. The mechanisms that mediate the effect of age on MSCs immune-regulatory function remain elusive and are the focus of this study. Human adipose tissue-derived MSCs were isolated from patients undergoing coronary artery bypass graft surgery. MSCs:CD4+T-cell suppression, a readout of MSCs’ immunopotency, was assessed in allogeneic coculture systems. MSCs from elderly subjects were found to exhibit a diminished capacity to suppress the proliferation of activated T cells. Soluble factors and, to a lesser extent, direct cell-cell contact mechanisms mediated the MSCs:T-cell suppression. Elderly MSCs exhibited a pro-inflammatory secretome with increased le...
Hematopoietic stem and progenitor cell (HSPC) homeostasis declines with age, leading to impaired ... more Hematopoietic stem and progenitor cell (HSPC) homeostasis declines with age, leading to impaired hematopoiesis. Mesenchymal stromal cells (MSC) are critical components of the bone marrow niche and key regulators of the balance between HSPC proliferation and quiescence. Accrual of DNA damage, a hallmark of cellular aging, occurs in aged MSC. Whether MSC aging alters the bone marrow niche triggering HSPC dysfunction is unknown. Using a human MSC-HSPC co-culture system, we demonstrated that DNA damaged MSC have impaired capacity to maintain CD34+CD38- HSPC quiescence. Furthermore, human MSC from adult donors display some hallmarks of cellular senescence and have a decreased capacity to maintain HSPC quiescence and the most primitive CD34+CD38- subset compared to MSC from pediatric donors. IL-6 neutralization restores the MSC-HPSC crosstalk in senescent and adult MSC-HSPC co-cultures highlighting the relevance of the local microenvironment in maintaining HSPC homeostasis. These results ...
Abnormal innate and adaptive immune responses are critically involved in the pathogenesis of rheu... more Abnormal innate and adaptive immune responses are critically involved in the pathogenesis of rheumatoid arthritis (RA). Anti-inflammatory and immunosuppressive therapies have been highly successful, but a cure for the disease has remained elusive, mostly due to lack of knowledge of disease instigators and the causative immune system abnormalities. RA is associated with premature aging of the immune system, which has been attributed to the chronic inflammatory milieu. However, recent data draw attention to processes of impaired immune regeneration as an underlying defect. Specifically, bone marrow hematopoietic stem cells (HSCs), permanently regenerating myeloid and lymphoid lineages, are functionally defective in RA, jeopardizing repopulation of the immune system. In RA, the pool of circulating HSCs is contracted and HSCs respond inadequately to hematopoietic growth factors. Most importantly, RA HSCs have age-inappropriate telomeric shortening, indicative of excessive proliferative stress. Defects in HSCs broaden the immunopathogenesis of RA to include early events in the shaping of the immune system. Restoring HSC function will be a necessary step in re-establishing immune health in RA patients. aging n DNA damage n hematopoiesis n hematopoietic stem cells n HSC n RA n rheumatoid arthritis n senescence n telomerase n telomeres
Proteasomes are targets of humoral autoimmune response in patients with connective tissue disease... more Proteasomes are targets of humoral autoimmune response in patients with connective tissue diseases and other organ-specific autoimmune diseases. The finding of circulating proteasomes in psoriasis, the multiplicity of mechanisms regulated by proteasomes that are also implicated in the pathogenesis of psoriatic arthritis (PsA), and the increasing evidence linking PsA and autoimmunity led us to evaluate whether the 20S proteasome represents an antibody target in PsA. Serum samples from 36 patients with PsA and 30 age- and sex-matched healthy subjects were tested for the presence of anti-20S proteasome antibodies (anti-20S antibody). Additional controls included 24 patients with systemic lupus erythematosus (SLE) and 20 with rheumatoid arthritis (RA). The associations of anti-20S antibodies with clinical, laboratory, and therapeutic measures were evaluated. 27.8% of the PsA patients were positive for anti-20S antibody compared to 41.6% of the SLE group and 5% of the RA group. None of t...
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