Increased activation-induced cell death in peripheral lymphocytes of rheumatoid arthritis patients: the mechanism of action

Response of human peripheral blood monocyte-derived macrophages (PBMM) to demineralized and decellularized bovine bone graft substitutes

The performance of apparently biocompatible implanted bovine bone grafts may be compromised by unresolved chronic inflammation, and poor graft incorporation leading to implant failure. Monitoring the intensity and duration of the inflammatory response caused by implanted bone grafts is crucial. In this study, the ability of demineralized (DMB) and decellularized (DCC) bovine bone substitutes in initiating inflammatory responses to peripheral blood monocyte-derived macrophages (PBMMs) was investigated. The response of PBMMs to bone substitutes was evaluated by using both direct and indirect cell culture, reactive oxygen species (ROS) generation, apoptosis, immunophenotyping, and cytokine production. Analysis of DMB and DCC substitutes using scanning electron microscope (SEM) showed a roughened surface with a size ranging between 500 and 750 μm. PBMMs treated with DMB demonstrated cell aggregation and clumping mimicking lipopolysaccharide (LPS) treated PBMMs and a higher proliferation ability (166.93%) compared to control (100%) and DCC treatments (115.64%; p<0.001) at 24h. This was associated with a significantly increased production of intracellular ROS in PBMMs exposed to DMB substitutes than control (3158.5 vs 1715.5; p<0.001) and DCC treatment (2117.5). The bone substitute exposure also caused an increase in percentage apoptosis which was significantly (p<0.0001) higher in both DMB (27.85) and DCC (29.2) treatment than control (19.383). A significant increase in proinflammatory cytokine expression (TNF-α: 3.4 folds; p<0.05) was observed in DMB substitute-treated PBMMs compared to control. Notably, IL-1β mRNA was significantly higher in DMB (21.75 folds; p<0.0001) than control and DCC (5.01 folds). In contrast, DCC substitutes exhibited immunoregulatory effects on PBMMs, as indicated by the expression for CD86, CD206, and HLDR surface markers mimicking IL-4 treatments. In conclusion, DMB excites a higher immunological response compared to DCC suggesting decellularization process of tissues dampen down inflammatory reactions when exposed to PBMM.

PDCD5 as a Potential Biomarker for Improved Prediction of the Incidence and Remission for Patients with Rheumatoid Arthritis

INTRODUCTION

Rheumatoid arthritis (RA) often involves an altered T-cell subpopulation, higher levels of inflammatory cytokines, and auto-antibodies. This study investigated whether PDCD5 could be a biomarker to predict the incidence and remission of RA so as to guide the therapeutic management of clinical RA.

METHODS

One hundred fifty-two patients (41 being in both active status and stable remission status) who were newly diagnosed with RA and 38 healthy controls were enrolled. Basic clinical data were collected before using blood samples remaining in the clinic after routine complete blood count. The ability of PDCD5 and important indicators to predict the remission of RA was estimated based on receiver operating characteristic curve (ROC) analysis.

RESULTS

PDCD5 expression was found to be significantly increased in RA patients in active status in comparison with healthy controls or those in stable remission status. Compared with anti-CCP, ESR and DAS28 score, PDCD5 was of better predictive value with an AUC of 0.846 (95% CI 0.780-0.912) for RA remission. The incidence risk of RA increased with higher levels of PDCD5 (OR = 1.73, 95% CI = 1.45-1.98, P = 0.005) in multiple logistic regression analysis, with the risk increasing by 2.94-times for high-risk group in comparison with low-risk group (OR = 2.94, 95% CI = 2.35-4.62, P < 0.001). The association between PDCD5 and RA remission showed a similar result. For correlation analysis, significant associations were eventually found between PDCD5 and indicated genes (FOXP3, TNF-α, IL-17A, IFN-γ and IL-6) as well as several important clinical parameters including IgG, RF, CRP, ESR, anti-CCP and DAS28 score.

CONCLUSIONS

This study suggested that increased PDCD5 expression was significantly linked to the incidence and remission of RA. PDCD5 may be used as a novel biomarker for the prediction of RA incidence and remission, especially due to its potential involvement in the development of the condition.

Telomere Length of Individual Chromosomes in Patients with Rheumatoid Arthritis

We analyzed telomere length of individual chromosomes in peripheral blood lymphocytes of healthy individuals and patients with rheumatoid arthritis. Quantitative fluorescent in situ hybridization and subsequent computer analysis of metaphase chromosomes showed that distribution of telomere length on individual chromosomes is different under normal and pathological conditions. Patients with rheumatoid arthritis had significantly shorter chromosome 4p telomeres, which can be essential for pathogenesis of this multifactorial disease. Additionally, disease activity inversely correlated with telomere length on chromosome 10p carrying genes involved in T cell differentiation and proliferation.

Resistance to activation-induced cell death and elevated FLIPL expression of CD4+ T cells in a polyI:C-induced primary biliary cirrhosis mouse model

Primary biliary cirrhosis (PBC) is a type of organ-specific autoimmune disease in which immune tolerance is impaired by an unknown mechanism. We established a PBC animal model by injecting C57BL/6 mice with polyI:C to study activation-induced cell death (AICD) in CD4+ T lymphocytes and changes of apoptosis-associated molecules as a first step to understand the immune tolerance of PBC mice. Obvious inflammatory cell infiltration was observed in the portal area of the liver tissues in model mice and antimitochondrial antibodies (AMA) positive rate was 80%. The AICD level in both splenic and hepatic CD4+ T cells in the model group were all lower than those in controls, and in the model group the level for hepatic CD4+ T cells were significantly lower than that for splenic CD4+ T cells. Quantitative PCR revealed that FasL mRNA and TRAIL expression in CD4+ T cells in the model group decreased significantly compared with that in the control group. Western blots revealed that the expression of the anti-apoptotic protein FLIP(L) in the model group increased significantly with the FLIP(L) expression in hepatic CD4+ T cells significantly higher than that in splenic CD4+ T cells. There was a positive linear correlation between the number of infiltrated portal areas and relative expression of FLIP(L) in splenic CD4+ T cells in model group. There were no obvious changes for caspase-8 in either group. These results show that the anti-apoptotic ability of CD4+ T lymphocytes play an important role in immune tolerance in the PBC mouse model, and elevated FLIP(L) expression may enhance this ability. The inhibition of FasL and TRAIL expression may also help enhance this anti-apoptotic ability in CD4+ T lymphocytes and contribute to the aggravation of portal area inflammation.

Engagement of CD44 up-regulates Fas ligand expression on T cells leading to activation-induced cell death

Activation-induced cell death (AICD) plays a pivotal role in self-tolerance by deleting autoreactive T cells, but a defect of AICD results in expansion of autoreactive T cells and is deeply involved in the pathogenesis of rheumatoid arthritis. Although the process of AICD is mainly mediated by Fas Ligand (FasL)/Fas signaling, it remains unclear what induces FasL expression on T cells. In the present study, we found that CD44 was the most potent stimulator of FasL expression on human peripheral T cells. CD44 cross-linking rapidly up-regulated FasL expression on the T cell surface by delivery from the cytoplasm without new FasL protein synthesis. This up-regulation of FasL was mediated by activation of a tyrosine kinase, IP3 receptor-dependent Ca(2+) mobilization and actin cytoskeletal rearrangements. Furthermore, AICD induced by CD3 restimulation was inhibited by hyaluronidase as well as by soluble Fas, indicating an interaction between membrane-bound hyaluronan and the cell surface CD44 was involved in the up-regulation of FasL expression on T cells and subsequent AICD. We therefore propose that the engagement of CD44 on T cells can eliminate autoreactive T cells by expression of FasL and FasL-mediated AICD.

Altered collagen II peptides inhibited T-cell activation in rheumatoid arthritis

It has been reported that collagen II (CII)-derived peptide induced T-cell activation via its amino acids responsible for T-cell receptor (TCR) recognition. In this study, three altered CII263-272 peptide ligands (APL) containing multiple substitutions of TCR contact residues were synthesized. Their roles in inhibition of T-cell activation were evaluated in peripheral blood lymphocytes (PBL) of rheumatoid arthritis (RA) in vitro. It was shown that 41% (25/61) of RA patients were responsive to the wild-type antigenic CII263-272. In contrast, marginal or silent T-cell responses to the three APLs were found, accompanied by inhibitory effects on secretion of Th1 type cytokines and expression of cell surface markers, CD69 and CD25. In addition, T-cell activation induced by the wild-type antigenic CII263-272 was inhibited by all the three APLs in a dose-dependent manner. It is demonstrated that APLs with substitutions of TCR contact residues are capable of down-regulating T-cell responses in PBLs of RA, suggesting that the CII-derived APLs are potentially therapeutic in RA.

T cell-mediated immunotherapy of metastases: state of the art in 2005

Advances in cellular and molecular immunology have led to the development of strategies for effective augmentation of antitumour immune responses in cancer patients. This review focuses on the manipulation of T cell immunity either by active specific immunotherapy (ASI) using tumour vaccines, or by adoptive immunotherapy (ADI) with immune T cells. Such therapies offer exquisite specificity of tumour recognition based on the ability of the T cell to distinguish single amino acid differences in any protein from any compartment of the tumour cell. Examples are presented of clinical survival benefits for cancer patients by postoperative ASI with a modified autologous tumour vaccine of high quality. Furthermore, clinical studies employing ADI with T cells activated and expanded ex vivo have demonstrated 'proof of principle' that tumour-specific T cells are capable of mediating anticancer activity in vivo, as measured by regression of metastatic tumours. Translation of these findings into a standardised immunotherapy is, however, not easy and will require coordination and cooperation among academic, private and federal sectors.

Impaired activation-induced telomerase activity in PBMC of early but not chronic rheumatoid arthritis patients

Although telomerase activity is important in normal immune function, it is unclear whether telomerase or telomerase (dys)regulation plays a role in the pathogenic immune response in autoimmune diseases like rheumatoid arthritis (RA). In this study, we evaluated the dynamics of the activation-induced human telomerase reverse transcriptase (hTERT) response in RA patients and non-RA controls. The expression of the catalytic subunit of telomerase, hTERT, was measured in peripheral blood mononuclear cells (PBMC) of RA patients and controls after in vitro stimulation with anti-CD3 monoclonal antibody (mAb) using real-time PCR. Anti-CD3 mAb stimulation induced activation and proliferation of the T cells in all populations studied. In early RA patients with a disease duration of less than 1 year, the activation-induced hTERT mRNA levels were found to be reduced as compared to healthy controls (HC). Chronic RA patients, with a disease duration of more than 1 year, did not show these impaired hTERT mRNA levels after stimulation with anti-CD3 mAb. Decreased hTERT mRNA levels were also found in multiple sclerosis patients and patients suffering from flu-like symptoms, indicating that these deviations are not disease-specific. The impaired activation-induced hTERT response in PBMC may be a general response of the immune cells in cases of acute or chronic immune activation, presumably to control unwanted clonal expansions and to maintain the diversity of the TCR repertoire. Our results also indicate that clonal T cell expansions, described in RA, are probably not mediated by an elevated potency to express hTERT.