The apoptosis-1/Fas protein in human systemic lupus erythematosus

Cytotoxic CD8+ T cells may be drivers of tissue destruction in Sjögren's syndrome

Sjögren's syndrome is a chronic autoimmune disorder whose pathogenesis is poorly understood and that lacks effective therapies. Detailed quantitative and spatial analyses of tissues affected by Sjögren's syndrome were undertaken, including the quantitation of the frequency of selected cell-cell interactions in the disease milieu. Quantitative analyses of CD4⁺ T cell subsets and of CD8⁺ T cells in the labial salivary glands from untreated patients with primary Sjögren's syndrome revealed that activated CD8⁺ cytotoxic T cells (CD8⁺CTLs) were the most prominent T cells in these infiltrates. An accumulation of apoptotic glandular epithelial cells, mainly ductal and acinar cells, was observed, consistent with the impaired salivary secretion often observed in patients with this disease. FasL expressing activated CD8⁺ T cells were seen to accumulate around Fas expressing apoptotic epithelial cells. Quantitative analyses of apoptotic cell types and of conjugates between cytotoxic T cells and epithelial cells undergoing apoptosis suggest that Sjögren's syndrome is primarily driven by CD8⁺CTL mediated execution of epithelial cells mainly represented by ductal and acinar cells.

Both perforin and FasL are required for optimal CD8 T cell control of autoreactive B cells and autoantibody production in parent-into-F1 lupus mice

To test the relative roles of perforin (pfp) vs. FasL in CTL control of autoreactive B cell expansion, we used the parent-into-F1 model of murine graft-vs.-host disease in which donor CD8 CTL prevent lupus like disease by eliminating activated autoreactive B cells. F1 mice receiving either pfp or FasL defective donor T cells exhibited an intermediate short-term phenotype. Pairing of purified normal CD4 T cells with either pfp or FasL defective CD8 T cell subsets resulted in impaired host B cell elimination and mild lupus like disease that was roughly equivalent in the two experimental groups. Thus, in addition to major roles in tumor and intracellular pathogen control, pfp mediated CD8 CTL killing plays a significant role in controlling autoreactive B cell expansion and lupus downregulation that is comparable to that mediated by FasL killing. Importantly, both pathways are required for optimal elimination of activated autoreactive B cells.

Immunopathogenesis of systemic lupus erythematosus and rheumatoid arthritis: the role of aberrant expression of non-coding RNAs in T cells

Non-coding RNAs (ncRNAs), including microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), are RNA molecules that do not translate into protein. Both miRNAs and lncRNAs are known to regulate gene expression and to play an essential role in T cell differentiation and function. Both systemic lupus erythematosus (SLE), a prototypic systemic autoimmune disease, and rheumatoid arthritis (RA), a representative disease of inflammatory arthritis, are characterized by a complex dysfunction in the innate and adaptive immunity. T cells play a central role in cell-mediated immune response and multiple defects in T cells from patients with SLE and RA have been observed. Abnormality in T cell signalling, cytokine and chemokine production, T cell activation and apoptosis, T cell differentiation and DNA methylation that are associated closely with the aberrant expression of a number of miRNAs and lncRNAs have been implicated in the immunopathogenesis of SLE and RA. This review aims to provide an overview of the current state of research on the abnormal expression of miRNAs and lncRNAs in T cells and their roles in the immunopathogenesis of SLE and RA. In addition, by comparing the differences in aberrant expression of miRNAs and lncRNAs in T cells between patients with SLE and RA, controversial areas are highlighted that warrant further investigation.

Fas Regulates Macrophage Polarization and Fibrogenic Phenotype in a Model of Chronic Ethanol-Induced Hepatocellular Injury

The role of Fas-mediated apoptosis and its effect on proinflammatory cytokine production in early alcoholic liver disease has not been addressed. Wild-type mice (C57Bl/6) or mice with a functional mutation in the Fas ligand (B6.gld) were given either high-fat control diet or ethanol diet by intragastric cannulation for 2 or 4 weeks. Liver injury, hepatic lipid accumulation, and proinflammatory cytokine production associated with chronic ethanol consumption were largely prevented in B6.gld mice compared with wild-type mice. Conversely, B6.gld mice given ethanol exhibited increases in collagen deposition, hepatic collagen gene expression, and profibrogenic cytokines (eg, transforming growth factor-β and IL-13) and alterations in matrix remodeling proteins (eg, matrix metalloproteinases and tissue inhibitor of metalloproteinases) compared with wild-type mice. Hepatic F4/80(+) macrophage populations were increased significantly in B6.gld mice compared with wild-type mice; hepatic CD3(+) cell populations were not significantly different. Importantly, a shift toward the expression of M2/Th2 cytokines (eg, IL-4 and IL-13) after ethanol exposure was observed in B6.gld mice compared with classical M1 cytokine expression in wild-type mice under similar conditions. In isolated macrophages, stimulation of Fas receptor minimally enhances lipopolysaccharide-induced M1 cytokine production and significantly limits M2 cytokine production. These data support the hypothesis that Fas-mediated signaling is important for an early ethanol-induced proinflammatory response but limits the profibrogenic response, regulating collagen production in response to chronic ethanol.

Immunotherapy and radiation therapy: considerations for successfully combining radiation into the paradigm of immuno-oncology drug development

As the immunotherapy of cancer comes of age, adding immunotherapeutic agents to radiation therapy has the potential to improve the outcomes for patients with a wide variety of malignancies. Despite the enormous potential of such combination therapy, laboratory data has been lacking and there is little guidance for pursuing novel treatment strategies. Animal models have significant limitation in combining radiation therapy with immunotherapy and some of the limitations of preclinical models are discussed in this article. In addition to the preclinical challenges, radiation therapy and immunotherapy combinations may have overlapping toxicities, and for both types of therapy, early and late manifestations of toxicity are possible. Given these risks, special attention should be given to the design of the specific Phase I clinical trial that is chosen. In this article, we describe several Phase I design possibilities that may be employed, including the 3 + 3 design (also known as the cohort of 3 design), the continual reassessment method (CRM), and the time-to-event continual reassessment method (TITE-CRM). Efficacy end points for further development of combination therapy must be based on multiple factors, including disease type, stage of disease, the setting of therapy and the goal of therapy. While the designs for future clinical trials will vary, it is clear that these two successful modalities of therapy can and should be combined for the benefit of cancer patients.

Association of Fas gene polymorphisms with systemic lupus erythematosus: a meta-analysis

The Fas gene polymorphisms -670A/G (rs1800682) and -1377G/A (rs2234767) have been shown to be associated with systemic lupus erythematosus (SLE), but findings are not consistent. To clarify this point, a meta-analysis was performed. We searched PubMed, CNKI, CBM and Wanfang database. Meta-odds ratios (ORs) and 95 % confidence intervals (95 % CIs) were used to combine the data by fixed/random effects models based on heterogeneity test. The statistical analyses were conducted using Stata software. A total of seven studies involving 759 cases and 820 controls were considered in this study and ethnicity-specific meta-analysis was performed on Caucasian and Asian population. In overall population, meta-analysis revealed a trend toward to an association between SLE and Fas -670 A allele (OR = 1.310, 95 %CI = 1.028 ~ 1.670, P = 0.029). Similar results were detected in recessive model (OR = 1.626, 95 %CI = 1.104 ~ 2.395, P = 0.014) and in homozygous genotypic contrast (OR = 1.728, 95 %CI = 1.049 ~ 2.848, P = 0.032). Stratification by ethnicity indicated a significant association between SLE and the Fas -670A/G polymorphism in Asian population when allelic contrast (OR = 1.331, 95 %CI = 1.066 ~ 1.662, P = 0.011), homozygous genotypic contrast (OR = 1.848, 95 %CI = 1.164 ~ 2.932, P = 0.009) and dominant model were performed (OR = 1.542, 95 %CI = 1.045 ~ 2.275, P = 0.029). Meta-analysis of the Fas -1377G/A polymorphism indicated a significant association between SLE and the G allele in overall population (OR = 1.277, 95 %CI = 1.004 ~ 1.624, P = 0.046). The results from this meta-analysis provide evidence for the association between the Fas -670A/G and -1377G/A polymorphism and the risk of SLE. However, further studies are needed to draw a definitive conclusion.

The tumour necrosis factor/TNF receptor superfamily: therapeutic targets in autoimmune diseases

Autoimmune diseases are characterized by the body's ability to mount immune attacks on self. This results from recognition of self-proteins and leads to organ damage due to increased production of pathogenic inflammatory molecules and autoantibodies. Over the years, several new potential therapeutic targets have been identified in autoimmune diseases, notable among which are members of the tumour necrosis factor (TNF) superfamily. Here, we review the evidence that certain key members of this superfamily can augment/suppress autoimmune diseases.

Autoimmunity in common variable immunodeficiency: correlation with lymphocyte phenotype in the French DEFI study

Common variable immunodeficiency (CVID) is the most frequent clinically expressed primary immunodeficiency in adults and is characterized by primary defective immunoglobulin production. Besides recurrent infectious manifestations, up to 20% of CVID patients develop autoimmune complications. In this study, we took advantages of the French DEFI database to investigate possible correlations between peripheral lymphocyte subpopulations and autoimmune clinical expression in CVID adult patients. In order to analyse homogeneous populations of patients with precise clinical phenotypes, we first focused on patients with autoimmune cytopenia because they represent prototypic autoantibody mediated diseases. In a secondary analysis, we have tested our conclusions including all "autoimmune" CVID patients. We describe one of the largest European studies with 311 CVID patients, including 55 patients with autoimmune cytopenia and 61 patients with clinical or serologic autoimmune expression, excluding autoimmune cytopenia. We clarify previous reports and we confirm a very significant correlation between an increased proportion of CD21(low) B cells and CVID associated autoimmune cytopenia, but independently of the presence of other autoimmune disorders or of splenomegaly. Moreover, in CVID associated autoimmune cytopenia, T cells display an activated phenotype with an increase of HLA-DR and CD95 expression and a decrease in the naïve T cell numbers. Patients with other autoimmune manifestations do not harbour this "T and B cells phenotypic picture". In view of recent findings on CD21(low) B cells in CVID and RA, we suggest that both a restricted subset of B cells and a T cell help are required for a breakdown of B cell tolerance against membrane auto antigens in CVID.

Longevity of SLE-prone mice increased by dietary 2-mercaptoethanol via a mechanism imprinted within the first 28 days of life

In the preceding report, moderately lived-mice fed dietary 2-mercaptoethanol (2-Me) had their life extended, whereas long-lived mice were found to have the quality of life improved, but not extended, and did not develop high fat-diet obesity. In the present report, alteration of longevity of mice prone to develop spontaneous, systemic lupus erythematosus (SLE) by dietary 2-Me was determined. NZB, NZW, (NZW x NZB) F₁-hybrid, BXSB/MpJ, BXSB-Yaa+/J, MRL/MpJ and MRL/MpJ-Faslpr mice received drinking water, without or with 2-Me at concentrations of 10⁻³ or 10⁻² M. Therapeutic benefit was assessed by changes in longevity. The median survival of MRL/MpJ males was increased from 443 to 615 days and those of (NZW x NZB) F₁ and NZB males and females were increased approximately 2-fold. The most unexpected finding was that longevity of F₁ males was significantly extended irrespective of whether dietary exposure to 2-Me was initiated at 28 days of age, at 50 days of age, or initiated during gestation (and then terminated at weaning--28 days of age). Survival of F₁-hybrids in which treatment was initiated in utero or at 28 days of age was not significantly different, whereas if initiation was delayed until 50 days of age, survival was >200 days shorter. Survival of male MRL/MpJ-Fas lpr and BXSB/MpJ (Yaa-), two strains with genetically controlled accelerated SLE, was not altered by 2-Me when started at 50 days. Various alternatives are discussed regarding potential long-lasting mechanisms imprinted early in life. Even though present day treatments of rodent SLE are generally aimed at controlling specific immunological events, with or without survival benefits, or are procedures presently unsuitable for therapeutic use in humans, the findings presented herein seem worthy of clinical evaluation.

Expression of FasR, Fas-L and Bcl-2 in CD4+ and CD8+ subpopulations of T lymphocytes in the cord blood of healthy full-term newborns, is gender of influence?

PURPOSE

The expression of FasR, Fas-L and Bcl-2 on CD4+ and CD8+ T lymphocytes subpopulations from the cord blood were assayed. The results in blood from boys and girls were analyses separately and compared.

MATERIAL AND METHODS

Twenty four full-term newborns: 13 females and 11 males were included into the study. Blood from the umbilical vein was collected immediately after cutting the umbilical cord. The staining with monoclonal antibodies against CD4, CD8, FasR, Fas-L and Bcl-2 was performed within 2 hours after collection and followed with flow cytometry acquisition and analysis.

RESULTS

The percentage of CD4+ and CD8+ T lymphocytes and CD4+:CD8+ ratio was within normal range. The expression of FasR, Fas-L was higher on CD4+ T lymphocytes than on CD8+ T lymphocytes (10,36% vs 6,79% and 6,66% vs 5,63% respectively). The expression of Bcl-2 was comparable (91,9% and 93,75% respectively). The comparison between males and females showed higher percentage of CD4+ lymphocytes on lymphocytes from girls' blood (56% vs 38,69%, p=0.0003). The expression of FasR and Fas-L on CD4+ T lymphocytes was higher on CD4+ T lymphocytes from girls' blood (13,8% vs 7,53% and 6,8% vs 6,52% respectively) but without statistical significance. Bcl-2 expression was higher on CD4+ T lymphocytes from boys' blood (99,65% vs 89,7%) but without statistical significance. Similar pattern of FasR, Fas-L and Bcl-2 expression was noted on CD8+ T lymphocytes analysed separately for girls' and boys' blood origin cells. The difference in Bcl-2 expression was more prominent than on CD4+ T lymphocytes and reached statistical significance.

CONCLUSIONS

The lymphocytes from cord blood of boys showed the more immature immunophenotype than T lymphocytes from cord blood of girls'. Impaired apoptosis (as a consequence of low expression of FasR, Fas-L) in neonatal cells may contribute to prolonged inflammation in newborns after oxidative stress or infection.

Upregulation of Fas and downregulation of CD94/NKG2A inhibitory receptors on circulating natural killer cells in patients with new-onset psoriasis

BACKGROUND

Psoriasis has been considered as a T-helper 1 cell-mediated autoimmune disease driven by collaboration with multiple components of innate and acquired immune cells. Natural killer (NK) cells have been shown to bridge innate and acquired immunity, and thus could potentially contribute to the pathophysiology of psoriasis.

OBJECTIVES

To investigate the phenotypic changes of circulating NK cells in patients with new-onset psoriasis.

METHODS

Fifteen patients with plaque psoriasis (eight women and seven men) who visited our clinic after their first episode of psoriasis and did not have a history of previous systemic therapy or phototherapy participated in this study. Peripheral blood mononuclear cells were isolated and stained with a panel of antibodies against cell surface receptors expressed on T and/or NK cells and analysed by flow cytometry.

RESULTS

As compared with normal healthy volunteers, patients with new-onset psoriasis showed no significant changes in numbers of peripheral NK, NK-T or T cells. NK activating receptors 2B4, CD48, NKG2D, CD16 and CD56 were found to be unchanged in new-onset psoriasis. However, the expression of Fas (activation-induced death receptor) was upregulated, whereas the expression of the NK inhibitory receptors CD94 and NKG2A was dramatically reduced on NK cells of new-onset psoriasis. These changes occurred at the level of mean fluorescent intensity, but minimally affected percentages of cells expressing Fas, CD94 and NKG2A.

CONCLUSIONS

Our findings demonstrate that changes in the expression of Fas and CD94/NKG2A receptors on NK cells may occur during new-onset psoriasis, and are likely to contribute to the pathogenesis of psoriasis.

DcR3 as a diagnostic parameter and risk factor for systemic lupus erythematosus

In this study, we investigated the diagnostic value of serum death decoy receptor 3 (DcR3) for systemic lupus erythematosus (SLE). The possible pathogenic role of DcR3 in SLE was also assessed. Serum DcR3 levels of 90 SLE patients, 11 patients with rheumatic conditions and 123 healthy controls were determined by ELISA. In all, 43% of the SLE patients, 9% of patients with rheumatic conditions and 2.4% of the normal healthy individuals presented elevated serum DcR3 levels. A higher percentage of DcR3-positive SLE patients, compared with DcR3-negative SLE patients, showed abnormally high serum IgE levels, a surrogate marker of T(h)2-type immune responses. To determine the cause and effect relationship of DcR3 expression and a T(h)2-prone status, we studied young DcR3 transgenic (Tg) mice, whose transgene was driven by an actin promoter. These mice had IL-4 overproduction and augmented serum IgE levels, signs of dominant T(h)2 immune responses. To determine possible SLE pathogenic roles of DcR3, the T-cell-depleted bone marrow of DcR3 Tg mice was transplanted into lethally irradiated syngeneic C57BL/6 female mice. The recipients developed an SLE-like syndrome. They presented anti-dsDNA and anti-nuclear antibodies, along with renal and liver pathology compatible with that of SLE. In total, 90% of Tg bone marrow-transplanted mice, compared with 20% of wild-type bone marrow-transplanted mice, perished within 12 months after the transplantation. Our results showed that serum DcR3 could serve as an additional parameter for SLE diagnosis and that DcR3 secreted from cells of hematopoietic origin was SLE pathogenic in mice.

Overexpression of human decoy receptor 3 in mice results in a systemic lupus erythematosus-like syndrome

OBJECTIVE

Decoy receptor 3 (DcR3), a tumor necrosis factor receptor family member, is a secreted protein that can enhance cell survival by interfering with multiple apoptosis pathways. This study was undertaken to investigate the role of DcR3 in the pathogenesis of autoimmune disease.

METHODS

We generated transgenic mice with actin promoter-driven expression of human DcR3 and investigated the development of autoimmune disease in these mice.

RESULTS

T cell immune responses were compromised in young DcR3-transgenic mice. Beyond 5-6 months of age, transgenic mice developed a systemic lupus erythematosus (SLE)-like syndrome, with numerous features of the disease. They produced autoantibodies against double-stranded DNA. Their kidneys showed pathologic changes indicative of glomerular nephritis and IgG and C3 deposition, and proteinuria, leukocyturia, and hematuria, were evident. Aged transgenic mice also developed skin lesions and lymphocyte infiltration in the liver, and exhibited leukopenia, anemia, and thrombocytopenia. The SLE-like syndrome penetrance in DcR3-transgenic mice was sex associated, occurring in approximately 60% of females versus 20% of males. Exogenous recombinant DcR3 or endogenous DcR3 produced by transgenic T cells effectively protected T cells against activation-induced apoptosis in vitro. Probably as a consequence of this, CD4 cells with a phenotype of previous activation were increased in the peripheral blood of transgenic mice beyond 6 months of age.

CONCLUSION

These results show that DcR3 overexpression could lead to an SLE-like syndrome in mice.

Apoptotic cell death and lupus

Programmed cell death and the disposal of cell corpses by phagocytic cells are highly regulated ongoing processes essential for the survival and well-being of higher organisms. Abnormalities in the susceptibility of certain cells to receptor-induced death are known to lead to certain human diseases (e.g., autoimmune lymphoproliferative syndrome) and may contribute to the pathogenesis of systemic lupus erythematosus. Impaired clearance of apoptotic cells is also likely to be an important factor in lupus pathogenesis, though the biological basis of such a defect remains elusive. Finally, the process of apoptosis has been shown to contribute to lupus disease effector mechanisms. A better understanding of the role of apoptosis in lupus very likely will lead to improved diagnosis and therapy.

Autoimmunity in systemic lupus erythematosus: integrating genes and biology

Susceptibility to the autoimmune phenotype of systemic lupus erythematosus (SLE) is heritable. Linkage analysis and recent advances in the field of single nucleotide polymorphisms (SNPs) have resulted in the identification of several genetic loci and functional allelic variants of signaling proteins which have become the mainstay of understanding disease susceptibility and exploring the basis of autoimmunity in SLE. However, genetic heterogeneity and possible epistatic interactions among genetic elements have precluded replication of these findings in multiple population groups and thus complicated their interpretation. In this regard, the discovery that a plethora of normal signaling proteins are expressed in abnormal amounts in immune cells from patients with SLE has gained significance. Thus, the key to precise elucidation of the pathologic basis of autoimmunity in SLE lies in tying genetics and disease biology. This review highlights recent discoveries of important functional genetic variants and altered expression of normal signaling proteins that network together to disrupt peripheral tolerance and initiate the autoimmune process in SLE.

A homozygous Fas ligand gene mutation in a patient causes a new type of autoimmune lymphoproliferative syndrome

Autoimmune lymphoproliferative syndrome (ALPS) is characterized by lymphoproliferation and autoimmune clinical manifestations and is generally caused by defective Fas-mediated apoptosis. This report describes the first homozygous FASL gene mutation in a woman with clinical and immunologic features of ALPS. T-cell blasts from the patient did not induce FasL-mediated apoptosis on Fas-transfected murine L1210 or on Jurkat cells, and activation-induced cell death was impaired. Furthermore, Fas-dependent cytotoxicity was drastically reduced in COS cells transfected with the mutant FasL. In addition, FasL expression on T-cell blasts from the patient was similar to that observed in a healthy control, despite its bearing the high-producer genotype -844C/C in the FASL promoter. Sequencing of the patient's FASL gene revealed a new mutation in exon 4 (A247E). The location of A247E in the FasL extracellular domain and the conservation of the protein sequence of that region recorded in 8 species different from humans support the essential role of FasL COOH terminal domain in Fas/FasL binding. These findings provide evidence that inherited nonlethal FASL abnormalities cause an uncommon apoptosis defect producing lymphoproliferative disease, and they highlight the need for a review of the current ALPS classification to include a new ALPS type Ic subgroup.

T cells in crescentic glomerulonephritis

Crescent formation in glomerulonephritis (GN) is a manifestation of severe glomerular injury that usually results in a poor clinical outcome. In humans, crescentic GN is frequently associated with evidence of either systemic or organ-specific autoimmunity. T cells play a major role in initiation of adaptive immune responses that lead to crescentic injury. In experimental models of crescentic GN, Th1 predominant immune responses have been shown to promote crescent formation. Perturbation of regulatory T cell function may contribute to development of autoimmune crescentic GN. The presence of T cells and macrophages in crescentic glomeruli, frequently in the absence of humoral mediators of immunity, suggest a dominant effector role for T cells in crescentic GN. The association of cellular immune mediators with local fibrin deposition implicates cell-mediated "delayed-type hypersensitivity-like" mechanisms in crescent formation. Intrinsic renal cells also contribute to T cell-driven effector mechanisms in crescentic GN, via expression of MHC II and co-stimulatory molecules and by production of chemokines and cytokines that amplify leukocyte recruitment and injury.

Modulating apoptosis as a target for effective therapy

Alterations in cell proliferation and cell death are essential determinants in the pathogenesis and progression of several diseases such as cancer, neurodegenerative disorders or autoimmune diseases among others. Complex networks of regulatory factors determine whether cells proliferate or die. Recent progress in understanding the molecular changes offer the possibility of specifically targeting molecules and pathways to achieve more effective and rational therapies. Drugs that target molecules involved in apoptosis are used as treatment against several diseases. Candidates such as TNF death receptor family, caspase inhibitors, antagonists of the p53-MDM2 interaction, NF-kappaB and PI3K pathways and Bcl-2 family members have been targeted as cancer cell killing agents. Moreover, apoptosis of tumor cells can also be achieved by targeting the inhibitor of apoptosis proteins, IAPs, in addition to the classical antiproliferative approach. Disruption of STAT activation and interferon beta therapy have been used as a treatment to prevent the progression of some autoimmune diseases. In models of Parkinson's, Alzheimer's and amyotrophic lateral sclerosis, blocking of Par-4 expression or function, as well as caspase activation, prevents neuronal cell death. Finally, it has been shown that gene therapy may be an encouraging approach for treatment of neurodegenerative disorders.

Fas and Fas ligand expression on germinal center type-diffuse large B-cell lymphoma is associated with the clinical outcome

In recent years, diffuse large B-cell lymphoma (DLBCL) has been classified by DNA microarray analysis into the germinal center B-cell-like (GC) type, the activated B-cell-like (ABC) type and type 3. The latter two types can be collectively categorized as the non-GC (NGC) type. From the prognostic perspective, the GC type has a favorable clinical outcome when compared with the NGC type. The protein Fas induces apoptosis of lymphocytes by binding with the Fas ligand (FasL), and escape from such apoptosis is considered to lead to malignant transformation of the cells and unrestricted growth of lymphoma. We proposed a hypothesis that Fas/FasL expression could be possibly related with a better survival of GC type DLBCL and evaluated 69 DLBCL cases immunohistochemically with CD10, Bcl-6, MUM1, Fas and FasL. These lymphomas were classified as GC type (positive for CD10 or Bcl-6 and negative for MUM1) or NGC type. The GC type had a better overall survival rate than the NGC type (P = 0.0723). Among markers as given above, positive CD10 was the most significant prognostic factor for overall survival in total DLBCL (P < 0.05). In the GC type, Fas and FasL expressions were significantly associated with a favorable overall survival (Fas: P < 0.005; FasL: P < 0.05). Hence, Fas or FasL expression might contribute to a better prognosis of this type of DLBCL.

Apoptosis: the link between autoantibodies and leuko-/lymphocytopenia in patients with lupus erythematosus

OBJECTIVE

To analyse the relation between serum autoantibodies and leuko-/lymphocytopenia in patients with lupus erythematosus (LE).

METHODS

Laboratory routine analyses (white blood cell counts, autoantibody detection), and flow cytometry (annexin V, CD3, CD4, CD8, CD95, F(ab)2 anti-human IgG) have been performed in LE-patients versus healthy controls. In vitro, the influence of pooled serum containing anti-dsDNA antibodies has been analysed on the CD95 expression.

RESULTS

Leukocytes, lymphocytes, CD3+, CD3+ CD4+, and CD3+ CD8+ cells from LE-patients were significantly reduced compared with controls. Patients with autoantibodies had significantly lower absolute cell counts than those without. Apoptosis was increased in LE versus controls (p < 0.04). The percentage of CD95+ T-cells was increased, and the absolute number of CD95+ cells was reduced in LE. In vitro up-regulation of CD95 could be detected on T-cells of healthy donors. Induction of CD95 seems to be donor-dependent.

CONCLUSION

The data suggest that autoantibodies may be associated with blood cytopenias. CD95 seems to play a central role in this signalling cascade. The underlying mechanism is unclear, but seems to be autoantibody-related apoptosis induction.

Functional defect of regulatory CD4(+)CD25+ T cells in the thymus of patients with autoimmune myasthenia gravis

Thymus-derived CD4(+)CD25+ regulatory T (Treg) cells are essential for the maintenance of immunologic self-tolerance. Despite their critical role in the active suppression of experimental autoimmune disorders, little is known about their involvement in human autoimmune diseases. Myasthenia gravis (MG) is a CD4+ T cell-dependent autoimmune disease and the thymus is assumed to be the initiation site. To identify possible defects in the Treg cells in MG, we analyzed CD4(+)CD25+ cells in thymi from patients with MG compared to those from healthy subjects. We found a normal CD4(+)CD25+ number but a severe functional defect in their regulatory activity together with a decreased expression of the transcription factor, Foxp3, which is essential for T-cell regulatory function. The phenotypic analysis of CD4(+)CD25+ thymocytes revealed an increased number of activated effector cells with strong Fas expression in patients with MG. However, whatever their level of Fas, CD4(+)CD25+ thymocytes from patients with MG remained unable to suppress the proliferation of responding cells, indicating that the impaired Treg cell function is not due to contamination by activated effector T cells. These data are the first to demonstrate a severe functional impairment of thymic Treg cells in MG, which could contribute to the onset of this autoimmune disease.

A proinflammatory role for Fas in joints of mice with collagen-induced arthritis

Collagen-induced arthritis (CIA) is a chronic inflammatory disease bearing all the hallmarks of rheumatoid arthritis, e.g. polyarthritis, synovitis, and subsequent cartilage/bone erosions. One feature of the disease contributing to joint damage is synovial hyperplasia. The factors responsible for the hyperplasia are unknown; however, an imbalance between rates of cell proliferation and cell death (apoptosis) has been suggested. To evaluate the role of a major pathway of cell death – Fas (CD95)/FasL – in the pathogenesis of CIA, DBA/1J mice with a mutation of the Fas gene (lpr) were generated. The susceptibility of the mutant DBA-lpr/lpr mice to arthritis induced by collagen type II was evaluated. Contrary to expectations, the DBA-lpr/lpr mice developed significantly milder disease than the control littermates. The incidence of disease was also significantly lower in the lpr/lpr mice than in the controls (40% versus 81%; P < 0.05). However DBA-lpr/lpr mice mounted a robust immune response to collagen, and the expression of local proinflammatory cytokines such as, e.g., tumor necrosis factor α (TNF-α) and IL-6 were increased at the onset of disease. Since the contribution of synovial fibroblasts to inflammation and joint destruction is crucial, the potential activating effect of Fas on mouse fibroblast cell line NIH3T3 was investigated. On treatment with anti-Fas in vitro, the cell death of NIH3T3 fibroblasts was reduced and the expression of proinflammatory cytokines TNF-α and IL-6 was increased. These findings suggest that impairment of immune tolerance by increased T-cell reactivity does not lead to enhanced susceptibility to CIA and point to a role of Fas in joint destruction.

Fas ligand down-regulates cytokine-induced Fas receptor expression on insulinoma (NIT-1), but not islet cells, from autoimmune nonobese diabetic mice

In the pathogenesis of autoimmune type 1 diabetes, the apoptosis receptor Fas appears de novo on the surface of insulin-producing beta-cells. Fas expression is thought to be induced by proinflammatory cytokines, such as IL-1beta, interferon-gamma (IFNgamma), and TNFalpha, released by islet-infiltrating mononuclear cells. To determine whether beta-cells can modulate their sensitivity to apoptosis at the level of Fas, we investigated the effect of Fas ligand (FasL) on surface expression of Fas in NIT-1 insulinoma cells from nonobese diabetic (NOD) mice prone to autoimmune diabetes and islet cells from NOD and nonautoimmune BALB/c mice. In NIT-1 insulinoma cells, Fas expression induced by the cytokine combination IL-1beta and IFNgamma was reduced in the presence of FasL, whereas in islet cells Fas expression was unaffected by FasL. The effect of FasL on NIT-1 cells was evident during and after the induction of Fas expression by IL-1beta and IFNgamma. Thus, FasL down-regulates cytokine-induced Fas expression in NOD mouse-derived NIT-1 cells, but not in NOD or BALB/c mouse islets. The ability of NIT-1 cells to down-regulate Fas receptor in response to ligation is similar to that of a variety of tumor cells, which may use this mechanism to escape destruction by cytotoxic T cells. Islets apparently cannot protect themselves against FasL-induced apoptosis by down-regulating the Fas receptor. Understanding how NIT-1 insulinoma cells down-regulate Fas receptor in response to ligation by FasL has therapeutic implications for protecting normal beta-cells in autoimmune type 1 diabetes.

Increased intensities of fas expression on peripheral T-cell subsets in severe autoimmune thyroid disease

Fas (CD95)-Fas ligand (FasL; CD178)-induced apoptosis is necessary for the maintenance of self-tolerance. To clarify whether or not any abnormalities in the Fas-FasL system exist in patients with autoimmune thyroid disease (AITD), we examined the expression of Fas and FasL on peripheral T lymphocytes by three-color flow cytometry in 113 patients with AITD and 49 healthy controls. The intensities of Fas expression in both CD4(+) and CD8(+) T cells decreased in thyrotoxic patients with Graves' disease (GD), but increased in both patients with severe Hashimoto's disease (HD) undergoing treatment and seriously intractable patients with GD continuously positive for thyrotropin (TSH) receptor antibody despite treatment with antithyroid drugs for more than 5 years. The proportion of Fas expression was increased in CD4(+) T cells from patients with untreated GD, and in CD8(+) T cells from patients with severe HD. The proportion of CD8(+) T cells decreased in patients with severe HD. FasL were not expressed on T cells in controls and patients with AITD. These results indicate that (1). the intensities of Fas expression on peripheral T cells increase in severe autoimmune thyroid diseases and (2). both the intensity and the proportion of Fas expression may be important for the induction of apoptosis.

The levels of serum-soluble Fas in patients with rheumatoid arthritis and systemic sclerosis

Different defects in Fas/APO-1 interaction with its ligand or in signaling of apoptosis may contribute to autoimmune disease. The aim of this study was to examine whether elevated serum-soluble Fas (sFas) levels are associated with rheumatoid arthritis (RA) or systemic sclerosis (SSc). sFas level was assayed using a sandwich ELISA in serum from 37 patients with RA, 30 patients with SSc and 20 healthy controls. The RA patients were classified according to disease activity, anatomical joint damage, and the presence of pulmonary involvement. Presence of pulmonary fibrosis, CO diffusion capacity (DLCO) and skin score were determined in patients with SSc. Serum sFas levels were not significantly different between study groups. Serum sFas level in the active RA patients was significantly higher than in the patients with inactive disease (p < 0.05). The untreated active RA patients had significantly higher sFas level than healthy controls (p < 0.05). In RA patients, sFas level was significantly correlated with rheumatoid factor titer (p = 0.01), C-reactive protein (p < 0.05), and erythrocyte sedimentation rate (p < 0.05). The RA patients with severe joint damage had significantly higher sFas level than those with mild joint damage (p < 0.05). The untreated SSc patients had significantly higher sFas levels than the treated SSc patients and healthy controls (p < 0.01). Serum sFas level was not correlated with presence of pulmonary fibrosis, DLCO or skin score. The soluble Fas molecule may provide a useful additional marker for assessment of disease activity and severity in patients with RA.

Fascination with bacteria-triggered cell death: the significance of Fas-mediated apoptosis during bacterial infection in vivo

Increasing evidence indicates that bacterial pathogens have developed mechanisms to modulate the apoptotic signaling cascade of host cells and thereby cause disease. The Fas death receptor pathway is one of the most extensively investigated apoptotic signaling pathways. In this review we discuss the role of Fas signaling during the interplay between bacterial pathogens and the host in vivo.

Systemic lupus erythematosus and apoptosis: a question of balance

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by the presence of autoantibodies directed against a range of intracellular nucleoprotein targets. SLE patients are believed to develop an autoimmune response triggered by surface-exposed intracellular macromolecules translocated to the cell surface during apoptosis. Apoptosis-or programmed cell death-is a genetically controlled process initiated by two principal pathways. The extrinsic pathway is activated by the ligation of death receptors, and the intrinsic pathway emerges from mitochondria. As shown in fas-deficient mice and humans, the inability of the immune system to eliminate self-reactive lymphocytes by apoptosis can cause persistence of autoreactive cells and autoimmunity. However, as shown in complement deficiencies, increased apoptotic material and altered clearance of apoptotic cells is found in patients with SLE. These results suggest that what is found in rare individuals with genetic deficiencies that develop SLE or SLE-like disease may be found in the larger population of SLE patients as a common end point pattern of unbalanced process of both apoptosis and clearance of apoptotic material.

Enhancement of T cell apoptosis correlates with increased serum levels of soluble Fas (CD95/Apo-1) in active lupus

Peripheral T cell apoptosis is upregulated in active SLE, in parallel with high expression of both membrane-bound and soluble (s) Fas. Previous studies postulated that sFas down-regulates apoptosis in vitro through its blockade of the Fas-L of cytotoxic cells. We have investigated the extent of apoptosis and sFas levels in 14 patients with active (group A) and 11 with inactive SLE (group B). Fas was predominantly expressed by CD3+ cells from group A, whose increased serological levels of sFas were linearly correlated with the TUNEL positive cell population, whereas low titers paralleled a mild level of apoptosis in group B. This association was also investigated by measuring the effect of sFas on both cell proliferation and caspase activation. We found that incubation with sFas greatly suppressed proliferation of CD3+ cells, especially in group B, and in control cells from healthy donors whose content of CPP32 active products was significantly increased. We postulate that sFas promotes a pro-apoptogen effect, which would explain the high susceptibility to apoptosis in active lupus, and that the apoptosis program itself includes release of sFas to spread the death signal.

Fas expression on T cells and sFas in relapsing-remitting multiple sclerosis

OBJECTIVES

To investigate the proportions of peripheral blood CD4+/Fas+ and CD8+/Fas+ cells and serum sFas levels in relapsing-remitting multiple sclerosis (RRMS) patients with relapses (active RRMS), those without relapses (stable RRMS), and controls over 1 year.

MATERIAL AND METHODS

Sixteen RRMS patients and 10 controls were tested monthly. Cells were analyzed by dual immunofluorescence and the sFas levels by ELISA. There were 14 relapses which occurred 1223 days after the last control visits. The measurements performed at these visits in the active RRMS patients were considered as relapse-related, while the rest were regarded as relapse-unrelated.

RESULTS

In active RRMS patients the median of CD4+ Fas+ to total CD4+ and CD8+ Fas+ to total CD8+ from relapse-related measurements were higher than the median from relapse-unrelated measurements (P=0.003, 0.004, respectively). The median of CD4+ Fas+ to total CD4+ from relapse-unrelated measurements in active RRMS was higher compared with stable RRMS (P = 0.005) and controls (P = 0.004). The sFas level from relapse-unrelated measurements was also higher in active RRMS than in stable RRMS (P = 0.04) and in controls (P = 0.004).

CONCLUSIONS

We suggest that increased expression of Fas antigen on CD4+ subset and increased serum sFas level are valuable markers of clinical activity in MS.

Immunobiologic consequences of assist devices

The aberrant state of monocyte and T-cell activation resulting from these host-device interaction is accompanied by two parallel processes: (1) selective loss of Th1 cytokine-producing CD4 T cells through activation-induced cell death, and (2) unopposed activation of Th2 cytokine-producing CD4 T cells resulting in B-cell hyperreactivity and dysregulated immunoglobulin synthesis via Th2 cytokines and heightened CD40 ligand-CD40 interactions. The net result of these events is that on one hand the VAD recipient develops progressive defects in cellular immunity and is at increased risk of serious infection, and on the other hand the VAD recipient is more likely to develop allosensitization, posing a significant risk to successful transplant outcome.

A novel polymorphic CAAT/enhancer-binding protein beta element in the FasL gene promoter alters Fas ligand expression: a candidate background gene in African American systemic lupus erythematosus patients

A single-nucleotide polymorphism (SNP), identified at nucleotide position -844 in the 5' promoter of the FasL gene, lies within a putative binding motif for CAAT/enhancer-binding protein beta (C/EBPbeta). Electrophoretic mobility shift and supershift assays confirmed that this element binds specifically to C/EBPbeta and demonstrated that the two alleles of this element have different affinities for C/EBPbeta. In luciferase reporter assays, the -844C genotype had twice the basal activity of the -844T construct, and basal expression of Fas ligand (FasL) on peripheral blood fibrocytes was also significantly higher in -844C than in -844T homozygous donors. FasL is located on human chromosome 1q23, a region that shows linkage to the systemic lupus autoimmune phenotype. Analysis of 211 African American systemic lupus erythematosus patients revealed enrichment of the -844C homozygous genotype in these systemic lupus erythematosus patients compared with 150 ethnically matched normal controls (p = 0.024). The -844C homozygous genotype may lead to the increased expression of FasL, to altered FasL-mediated signaling in lymphocytes, and to enhanced risk for autoimmunity. This functionally significant SNP demonstrates the potential importance of SNPs in regulatory regions and suggests that differences in the regulation of FasL expression may contribute to the development of the autoimmune phenotype.

Increased bioactive TNF in human systemic lupus erythematosus: associations with cell death

In systemic lupus erythematosus (SLE) serum TNF is increased and correlates with its soluble receptors and with disease activity. We therefore investigated (i) whether the TNF in SLE serum is bioactive, (ii) whether SLE cells react to TNF and (iii) whether there are associations with cell death, which is regarded as pathogenic in SLE. Sera from active SLE patients induced an increase in fibroblast CD54, which was abolished by blocking antibodies against TNF, suggesting TNF bioactivity. SLE lymphocytes had a similar surface expression of TNF-RI as healthy lymphocytes, their expression of TNF-RII was slightly increased. Recombinant TNF induced cell death in PBMC of SLE patients, suggesting functional receptors. Serum levels of sTNF-RII (as a surrogate marker for TNF activity) correlated with sTNF-RI and disease activity, as expected, and also correlated with the percentage of dying lymphocytes and with lymphocytic CD95. SLE sera contain increased amounts of biologically active TNF. Peripheral blood lymphocytes of SLE patients express functional TNF receptors. Finally, associations with cell death and CD95 receptors suggest that TNF may be pathogenic in SLE.

The apoptotic ligands TRAIL, TWEAK, and Fas ligand mediate monocyte death induced by autologous lupus T cells

Individuals with systemic lupus erythematosus show evidence of a significant increase in monocyte apoptosis. This process is mediated, at least in part, by an autoreactive T cell subset that kills autologous monocytes in the absence of nominal Ag. We have investigated the apoptotic pathways involved in this T cell-mediated process. Expression of the apoptotic ligands TRAIL, TNF-like weak inducer of apoptosis (TWEAK), and Fas ligand on lupus T cells was determined, and the role of these molecules in the monocyte apoptotic response was examined. We report that these apoptotic ligands mediate the autologous monocyte death induced by lupus T cells and that this cytotoxicity is associated with increased expression of these molecules on activated T cells, rather than with an increased susceptibility of lupus monocytes to apoptosis induced by these ligands. These results define novel mechanisms that contribute to increased monocyte apoptosis characterizing patients with lupus. We propose that this mechanism could provide a source of potentially antigenic material for the autoimmune response and interfere with normal clearing mechanisms.

Treatment options for juvenile-onset systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an inflammatory chronic disease characterized by the presence of activated helper T-cells that induce a B-cell response, resulting in the secretion of pathogenic autoantibodies and the formation of immune complexes. SLE in children is a disease of low prevalence with a wide range of clinical manifestations, which means that the number of randomized controlled studies are few and usually involve a small number of patients. In recent years, new therapeutic agents have appeared and the role of older treatments has been clarified. Many of these treatments are designed to reduce inflammation. The spectrum is broad and ranges from traditional nonsteroidal anti-inflammatory drugs (NSAIDs) to cytotoxic agents that have anti-inflammatory effects. The current treatment of children or adults depends on the clinical expression of the disease. Minor manifestations usually respond to the administration of NSAIDs, low doses of corticosteroids, hydroxychloroquine, or methotrexate. Thalidomide could be used for refractory skin lesions. Major manifestations can endanger the patient's life and require early, aggressive treatment. Kidney disease and other manifestations have been related to the formation or deposit of tissular immune complexes. Therefore, for years the main aim of treatment has been to suppress the immune response. The immunosuppressant treatments used in children with SLE include high doses of corticosteroids, azathioprine, methotrexate, cyclosporine, and cyclophosphamide. Several combinations of medications have been used to obtain a rapid remission or to reduce the risk of toxicity of prolonged administration of cytotoxic agents. Intravenous gamma-globulin has been successfully used in the treatment of lupus nephritis, vasculitis, and acute thrombocytopenia. In spite of numerous published studies, the use of these drugs is still controversial. The immunosuppression achieved with these treatments is nonspecific, not always effective, and associated with significant toxicities; the most significant being growth retardation, accelerated atherosclerosis and severe infectious complications. The purpose of new biological therapies is to achieve specific immunosuppression, which makes it possible to design more effective and less toxic therapeutic strategies. Mycophenolate mofetil is a promising alternative in patients who do not respond to high doses of cyclophosphamide or azathioprine. Some recently developed monoclonal antibodies such as anti-CD40L or anti-IL-10, or other molecules such as LJP394 may prove useful in the near future. Finally, stem cell transplantation may be proposed in patients with severe juvenile-onset SLE who do not respond to any treatment.

Combination of molecular mimicry and aberrant autoantigen expression is important for development of anti-Fas ligand autoantibodies in patients with systemic lupus erythematosus

We have reported previously that circulating anti-Fas ligand (FasL) autoantibodies able to inhibit Fas/FasL-mediated apoptosis were present in patients with systemic lupus erythematosus (SLE). In the present study, we describe the epitopes recognized by these anti-FasL autoantibodies. Rabbit antihuman antibody, raised against a FasL fragment consisting of amino acids (aa) 103-179 (fragment 2.0), inhibited Fas/FasL-mediated apoptosis, whereas an antibody against a FasL aa 103-146 fragment (fragment 1.0) did not. This suggested that an epitope around aa 146-179 was important for Fas/FasL interaction. Epitope mapping of anti-FasL autoantibodies using deletion mutants indicated that the epitope was located around aa 163-179. Three-dimensional molecular modelling of the Fas/FasL complex revealed that the aa 162-169 region was located on the outermost side of FasL, which suggested that the anti-FasL autoantibody would easily have access to the epitope. FasL point mutants involving aa positions 162-169 resulted in complete loss of apoptosis-inducing capability, which suggested that the aa 162-169 region was important for Fas/FasL interaction. A synthetic FasL peptide consisting of aa 161-170 blocked the binding of anti-FasL autoantibodies to FasL fragment 2.0 (aa 103-179). The FasL aa 161-170 sequence was found to be highly homologous with aa sequences from several infectious agents. Synthetic peptides derived from some of these microorganisms cross-reacted with the epitope recognized by the autoantibodies, suggesting that several foreign infectious agent-derived proteins may share an epitope with human FasL. As lymphocytes from SLE patients aberrartly expressed FasL, it is possible that infection by one of several infectious agents may trigger cross-reactive antibody responses, after which aberrantly expressed endogenous FasL might induce the shift from a cross-reactive response to an authentic autoimmune response. Therefore, a combination of molecular mimicry and aberrant autoantigen expression may be important for the development of anti-FasL autoantibodies in SLE patients.

Fas expression on peripheral blood lymphocytes in systemic lupus erythematosus (SLE): relation to lymphocyte activation and disease activity

Levels of apoptotic lymphocytes have been found to be increased in SLE and persistence of apoptotic cells has been associated with autoantibody production. Increased lymphocyte Fas (CD95) expression due to lymphocyte activation may account for increased susceptibility to Fas-mediated apoptosis in SLE. Flowcytometry was performed to evaluate membrane expression of Fas in combination with the activation markers CD25, HLA-DR and CD38 on, respectively, CD4+, CD8+ and CD19+ lymphocytes of SLE patients with inactive (n = 20) and with active disease (n = 13). SLEDAI-scores were calculated. Healthy volunteers (n = 14) served as controls. Percentages of CD4+ T-cells expressing CD25 and CD19+ B-cells expressing CD38 were increased in patients with active disease compared to controls (P = 0.03, P = 0.04, respectively). In contrast to CD4+ and CD8+ cells, percentages of CD19+ cells expressing Fas were increased in SLE patients with active disease (P = 0.0002 vs controls). In these patients percentages of cells double positive for both CD38 and Fas were increased compared to patients with inactive disease (P = 0.006) and controls (P = 0.0007). Percentages of CD19+ cells expressing Fas correlated with SLEDAI-scores. In SLE patients, percentages of Fas-expressing B-lymphocytes are increased, are related to the state of lymphocyte activation, and correlate to disease activity. Increased Fas expression results in a higher susceptibility for Fas-mediated apoptosis, which might contribute to the increased levels of apoptotic lymphocytes in SLE patients.

Metabolic switches of T-cell activation and apoptosis

The signaling networks that mediate activation, proliferation, or programmed cell death of T lymphocytes are dependent on complex redox and metabolic pathways. T lymphocytes are primarily activated through the T-cell receptor and co-stimulatory molecules. Although activation results in lymphokine production, proliferation, and clonal expansion, it also increases susceptibility to apoptosis upon crosslinking of cell-surface death receptors or exposure to toxic metabolites. Activation signals are transmitted by receptor-associated protein tyrosine kinases and phosphatases through calcium mobilization to a secondary cascade of kinases, which in turn activate transcription factors initiating cell proliferation and cytokine production. Initiation and activity of cell death-mediating proteases are redox-sensitive and dependent on energy provided by ATP. Mitochondria play crucial roles in providing ATP for T-cell activation through the electron transport chain and oxidative phosphorylation. The mitochondrial transmembrane potential (DeltaPsi(m)) plays a decisive role not only by driving ATP synthesis, but also by controlling reactive oxygen species production and release of cell death-inducing factors. DeltaPsi(m) and reactive oxygen species levels are regulated by the supply of reducing equivalents, glutathione and thioredoxin, as well as NADPH generated in the pentose phosphate pathway. This article identifies redox and metabolic checkpoints controlling activation and survival of T lymphocytes.

Immunopathogenesis of lupus and lupus nephritis: recent insights

Systemic lupus erythematosus is a multisystemic autoimmune disease. The immunopathogenesis is characterized by the loss of tolerance to self. While many abnormalities in the immune system have been detected, genetic factors play a central role in the pathogenesis. The event proximate to target organ involvement appears to be autoantigen-driven, T cell-mediated, B cell activation. High levels of autoantibodies are produced. However, not all autoantibodies are pathogenic to the kidney (i.e. 'nephritogenic'). These nephritogenic autoantibodies appear to share specific physiochemical features that correlate well with patterns of renal injury. While DNA was initially regarded as the inciting autoantigen, this view does not appear to be supported by the prevailing evidence. Nucleosomes, which are structures comprising histones and DNA, have emerged as the more likely candidate autoantigen. Autoantibodies directed against nucleosomes that cross-react with nucleosomal epitopes have been identified. Furthermore, evidence suggests that immunoglobulin-nucleosomal complexes may be important in target organ immune deposition. In-vivo generation of nucleosomes requires apoptosis; in fact, there are several examples of aberrant apoptotic processes that present with autoimmunity. Aberrant apoptosis may also be critical in lupus immunopathogenesis. Indeed, studies on Fas/FasL and Bcl-2 in animal models and in humans have underscored the importance of apoptosis as an etiological factor in lupus. Cytokines, hormonal, infectious and environmental factors have also been found to be important in the pathogenesis of systemic lupus erythematosus. Overall, much progress has been made in elucidating the etiological agents and pathogenic mechanisms by which lupus develops. However, there is still some way to go before arriving at a unifying hypothesis. The reward for a better understanding of lupus immunopathogenesis will be the development of more specific targets for treatment, and the introduction of better and safer treatment modalities.

Of mice and men: the relevance of the mouse to the study of human SLE

A number of mouse models have been utilized to study the pathophysiology of immune complex (IC) disease, and the hallmark IC disease systemic lupus erythematosus (SLE). Many of these studies have provided exciting new insights into IC-mediated inflammation and autoimmunity. However, numerous differences exist between mice and humans that suggest that mouse studies are not always applicable to human disease. These differences can be found in the biological systems that interact with circulating IC, in the specifics of disease presentation, and in the general physiology of the two species. Furthermore, although the mechanisms of SLE-like autoimmune disease in the mouse are being defined through analyses of the murine models of SLE, it remains to be proven that these mechanisms are relevant to human SLE. Thus, generalizing the results of the mouse studies to human SLE and other human IC diseases must be done with caution.

Death-inducing receptors and apoptotic changes in lymphocytes of patients with heart transplant vasculopathy

The specific role of lymphocyte apoptosis and transplant-associated atherosclerosis is not well understood. The aim of our study was to investigate the impact of T cell apoptotic pathways in patients with heart transplant vasculopathy. Amongst 40 patients with cardiac heart failure class IV who have undergone heart transplantation, 20 recipients with transplant-associated coronary artery disease (TACAD) and 20 with non-TACAD were investigated one year postoperative. Expression of CD95 and CD45RO, and annexin V binding were measured by FACS. Soluble CD95, sCD95 ligand (sCD95L), tumour necrosis factor receptor type 1 (sTNFR1), and histones were measured in the sera by ELISA. The percentage of cells expressing CD3 and CD4 was significantly reduced in TACAD as well as in non-TACAD patients as compared with control volunteers. Interestingly, the proportion of CD19+ (B cells) and CD56+ (NK) cells was increased in TACAD groups (versus non-TACAD; P < 0.01, and P < 0.001, respectively). In contrast to sCD95, the expression of CD95 (APO-1/Fas) and CD45RO (memory T cells), and sCD95L were significantly increased in non-TACAD and TACAD patients. T cell activation via CD95 with consecutive apoptosis was increased in both groups. The concentration of sTNFR1, IL-10 and histones was significantly elevated in sera from TACAD than non-TACAD patients, and in both groups than in healthy controls. These observations indicate that the allograft may induce a pronounced susceptibility of CD4+ T cells to undergo apoptosis and antibody-driven activation-induced cell death. This data may suggest a paradox immune response similar to that seen in patients with autoimmune diseases.

Mitochondrial hyperpolarization and ATP depletion in patients with systemic lupus erythematosus

OBJECTIVE

Peripheral blood lymphocytes (PBLs) from systemic lupus erythematosus (SLE) patients exhibit increased spontaneous and diminished activation-induced apoptosis. We tested the hypothesis that key biochemical checkpoints, the mitochondrial transmembrane potential (deltapsim) and production of reactive oxygen intermediates (ROIs), mediate the imbalance of apoptosis in SLE.

METHODS

We assessed the deltapsim with potentiometric dyes, measured ROI production with oxidation-sensitive fluorochromes, and monitored cell death by annexin V and propidium iodide staining of lymphocytes, using flow cytometry. Intracellular glutathione levels were measured by high-performance liquid chromatography, while ATP and ADP levels were assessed by the luciferin-luciferase assay.

RESULTS

Both deltapsim and ROI production were elevated in the 25 SLE patients compared with the 25 healthy subjects and the 10 rheumatoid arthritis patients. Intracellular glutathione contents were diminished, suggesting increased utilization of reducing equivalents in SLE. H2O2, a precursor of ROIs, increased deltapsim and caused apoptosis in normal PBLs. In contrast, H2O2-induced apoptosis and deltapsim elevation were diminished, particularly in T cells, and the rate of necrotic cell death was increased in patients with SLE. The intracellular ATP content and the ATP:ADP ratio were reduced and correlated with the deltapsim elevation in lupus. CD3:CD28 costimulation led to transient elevation of the deltapsim, followed by ATP depletion, and sensitization of normal PBLs to H2O2-induced necrosis. Depletion of ATP by oligomycin, an inhibitor of F0F1-ATPase, had similar effects.

CONCLUSION

T cell activation and apoptosis are mediated by deltapsim elevation and increased ROI production. Mitochondrial hyperpolarization and the resultant ATP depletion sensitize T cells for necrosis, which may significantly contribute to inflammation in patients with SLE.

Enhanced peripheral T-cell apoptosis in chronic hepatitis C virus infection: association with liver disease severity

BACKGROUND/AIMS

It has been suggested that enhanced T-cell apoptosis in hepatitis C virus (HCV) infection may lead to down-regulation of their cellular immune response, thus contributing to the persistency of HCV infection. In the present study we have investigated the role of bcl-2 and nuclear factor kappa B (NFkappaB) in dexamethasone-induced apoptosis of peripheral T cells in chronic HCV infection.

METHODS

The expression of bcl-2 and NFkappaB in peripheral T cells as well as spontaneous and dexamethasone-induced T-cell apoptosis were studied in HCV-infected patients (n=21), hepatitis B virus (HBV)-infected patients (n=14) and healthy individuals (n=19). These parameters were correlated with markers of autoimmunity and disease severity.

RESULTS

NFkappaB, but not bcl-2 expression, was significantly decreased in the HCV-infected patients. This decrease was associated with the presence of mixed cryoglobulins (MC) and rheumatoid factor and was positively correlated with alanine aminotransferase (ALT) levels and histological activity index (HAI). Both spontaneous and dexamethasone-induced T-cell apoptosis were enhanced in HCV-infected patients; however, only the latter was correlated with the presence of MC, ALT levels and HAI.

CONCLUSIONS

We confirm previous reports that enhanced T-cell apoptosis in HCV infection may play an important role in disease severity. Decreased expression of NFkappaB is important in the development of peripheral T-cell apoptosis, thus contributing to viral persistence and autoimmunity in these patients.

Effects of dexamethasone on the expression of Fas molecules and apoptosis of lymphocytes in patients with systemic lupus erythematosus

Previous studies have shown that the autoimmune phenomenon could be caused by defective apoptosis of autoreactive lymphocytes. Corticosteroids used for treatment of systemic lupus erythematosus (SLE) are potent apoptosis inducers. We examined dexamethasone (DEX)-induced apoptosis and Fas expression in peripheral blood lymphocytes of SLE patients and normal subjects. Peripheral blood lymphocytes were obtained from 40 SLE patients and 18 sex- and age-matched control subjects. Percentages of apoptosis and expression of Fas molecule in lymphocytes were assessed by flow cytometry. Fas expression in lymphocytes treated with or without DEX was significantly higher in SLE patients than normal controls [median (interquartile range) of mean fluorescence intensity without DEX: 74.9 (50.7-98.0) vs 20.0 (17.7-25.0), p < 0.001; with DEX: 77.9 (56.0-130.5) vs 20.5 (18.6-24.7), p<0.001]. DEX (0.1-5 microM) could also induce apoptosis of lymphocytes from SLE and control subjects in a dose-dependent manner. Elevation of apoptotic susceptibility was more prominent in DEX-treated SLE lymphocytes [33.9% (24.7-37.5%) vs 19.6% (13.6-26.1 %), p = 0.003]. The higher apoptotic susceptibility of SLE lymphocytes upon DEX treatment in vitro may be related, at least partly, to the pharmacological action of corticosteroids.

Apoptotic cell death in the pathogenesis of infectious diseases

Apoptosis is a physiological process critical for tissue homeostasis. It is essential for the regulation of immune responses. A series of molecules transduce apoptoic signals and induce the characteristic morphological appearances of apoptotic cells. Infectious diseases modulate apoptosis and this contributes to disease pathogenesis. Infection with HIV results in enhanced levels of CD4 T-lymphocyte apoptosis in both directly infected cells and in uninfected bystander cells. A variety of HIV proteins including gp120 contribute to this process. A number of different pathways induce HIV-associated CD4 T-lymphocyte apoptosis and apoptosis of uninfected bystander cells is particularly associated with increased susceptibility to Fas. Other viruses including hepatitis viruses and the human herpesviruses also modulate apoptosis. Bacterial infection induces apoptosis which is frequently mediated by the direct activation of caspases in the absence of death receptor ligation. Bacterial induction of apoptosis may either be due to bacterial factors such as the invasin IpaB of Shigella flexneri or be the result of host immune responses which control infection as demonstrated in infections due to Mycobacterium spp. Apoptosis may be modulated by therapeutic strategies, such as antiretroviral therapy, and an improved understanding of infection-associated apoptosis modulation will aid the design of novel therapeutic approaches to control infectious diseases.

The regulation of FasL expression--a distinquishing feature between monocytes and T lymphocytes/NK cells with possible implications for SLE

Monocytes and lymphocytes from patients with systemic lupus erythematosus (SLE) had a higher cell surface expression of FasL than the corresponding cells from healthy individuals. Inhibitors of metalloproteases upregulated the surface expression of FasL in peripheral blood lymphocytes (PBL), indicating that a metalloprotease is responsible for the cleavage of FasL. The level of sFasL in serum was slightly increased in the patient group compared to the controls. Therefore, the possible contribution of various mononuclear cell types to the release of FasL was analyzed. Isolated NK cells and T lymphocytes released FasL into the medium and the release was prevented by inhibitors of metalloproteases. In contrast, isolated monocytes did not release FasL. FasR expression was elevated in patients with inverted CD4/CD8 ratio, while FasL expression showed no relationship to CD4/CD8 ratio. The absence of FasL release by isolated cells and a high level of surface expression of FasL distinguish monocytes and T lymphocytes/NK cells.