Upregulated expression and function of integrin adhesive receptors in systemic lupus erythematosus patients with vasculitis

Tetraspanin CD53 modulates lymphocyte trafficking but not systemic autoimmunity in Lyn-deficient mice

The leukocyte-restricted tetraspanin CD53 has been shown to promote lymphocyte homing to lymph nodes (LNs) and myeloid cell recruitment to acutely inflamed peripheral organs, and accelerate the onset of immune-mediated disease. However, its contribution in the setting of chronic systemic autoimmunity has not been investigated. We made use of the Lyn^-/- autoimmune model, generating Cd53^-/- Lyn^-/- mice, and compared trafficking of immune cells into secondary lymphoid organs and systemic autoimmune disease development with mice lacking either gene alone. Consistent with previous observations, absence of CD53 led to reduced LN cellularity via reductions in both B and T cells, a phenotype also observed in Cd53^-/- Lyn^-/- mice. In some settings, Cd53^-/- Lyn^-/- lymphocytes showed greater loss of surface L-selectin and CD69 upregulation above that imparted by Lyn deficiency alone, indicating that absence of these two proteins can mediate additive effects in the immune system. Conversely, prototypical effects of Lyn deficiency including splenomegaly, plasma cell expansion, elevated serum immunoglobulin M and anti-nuclear antibodies were unaffected by CD53 deficiency. Furthermore, while Lyn^-/- mice developed glomerular injury and showed elevated glomerular neutrophil retention above than that in wild-type mice, absence of CD53 in Lyn^-/- mice did not alter these responses. Together, these findings demonstrate that while tetraspanin CD53 promotes lymphocyte trafficking into LNs independent of Lyn, it does not make an important contribution to development of autoimmunity, plasma cell dysfunction or glomerular injury in the Lyn^-/- model of systemic autoimmunity.

Identification of neutrophil β2-integrin LFA-1 as a potential mechanistic biomarker in ANCA-associated vasculitis via microarray and validation analyses

BACKGROUND

Leukocyte activation by anti-neutrophil cytoplasmic antibody (ANCA) and the subsequent leukocyte-endothelium interaction play a key role in the development of endothelial damage in ANCA-associated vasculitis (AAV). In contrast to that of leukocyte activation, the exact role of the leukocyte-endothelium interaction via integrin remains unclear. Here, we performed microarray and validation analyses to explore association between the expression levels of lymphocyte function-associated antigen-1 (LFA-1) and the clinical characteristics of patients with AAV.

METHODS

We performed gene set enrichment analysis (GSEA) to identify the functional gene sets differentially expressed between patients with AAV and other types of vasculitis and the healthy controls (HCs). Flow cytometry was performed to validate the GSEA results. Treatment-naïve patients were monitored until 24 weeks of treatment. To examine the role of LFA-1 in the neutrophil-endothelium interaction, we performed a leukocyte adhesion and transmigration assay using peripheral blood and human umbilical vein endothelial cells (HUVECs).

RESULTS

GSEA revealed that the molecular pathways involving integrin-related genes were significantly upregulated in patients with AAV compared to that in patients with other types of vasculitis and the HCs. Flow cytometry revealed that the percentage of neutrophils expressing LFA-1 was significantly higher in patients with AAV than in those with large-vessel vasculitis or polyarteritis nodosa and the HCs. LFA-1 levels in the neutrophils were higher in patients with MPO-ANCA-positive expression than in those with a positive PR3-ANCA expression and correlated with the peripheral eosinophil count, serum rheumatoid factor titre, serum C-reactive protein levels, and the vasculitis activity score of systemic and chest components. After 24 weeks of treatment, including prednisolone, cyclophosphamide, rituximab, azathioprine, methotrexate, and/or tacrolimus, neutrophil LFA-1 expression remained high in the non-responder patients, but decreased in the responder patients. The in vitro assay showed that leukocyte migration toward HUVECs was dependent on the interaction between LFA-1 and intercellular adhesion molecule-1 (ICAM1); the migration of leukocytes was inhibited by blocking the adhesion of LFA-1 to ICAM1.

CONCLUSIONS

The expression of LFA-1 in neutrophils is increased in patients with AAV. Neutrophil LFA-1 levels correlate with the clinical features of AAV. Inhibiting the adhesion of LFA-1 and ICAM1 impedes the neutrophil-endothelium interaction and may have a therapeutic role in AAV.

The Epigenetics of Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a life-threatening autoimmune disease that is characterized by dysregulated dendritic cells, T and B cells, and abundant autoantibodies. The pathogenesis of lupus remains unclear. However, increasing evidence has shown that environment factors, genetic susceptibilities, and epigenetic regulation contribute to abnormalities in the immune system. In the past decades, several risk gene loci have been identified, such as MHC and C1q. However, genetics cannot explain the high discordance of lupus incidence in homozygous twins. Environmental factor-induced epigenetic modifications on immune cells may provide some insight. Epigenetics refers to inheritable changes in a chromosome without altering DNA sequence. The primary mechanisms of epigenetics include DNA methylation, histone modifications, and non-coding RNA regulations. Increasing evidence has shown the importance of dysregulated epigenetic modifications in immune cells in pathogenesis of lupus, and has identified epigenetic changes as potential biomarkers and therapeutic targets. Environmental factors, such as drugs, diet, and pollution, may also be the triggers of epigenetic changes. Therefore, this chapter will summarize the up-to-date progress on epigenetics regulation in lupus, in order to broaden our understanding of lupus and discuss the potential roles of epigenetic regulations for clinical applications.

The Pathogenic Role of Dysregulated Epigenetic Modifications in Autoimmune Diseases

Autoimmune diseases can be chronic with relapse of inflammatory symptoms, but it can be also acute and life-threatening if immune cells destroy life-supporting organs, such as lupus nephritis. The etiopathogenesis of autoimmune diseases has been revealed as that genetics and environmental factors-mediated dysregulated immune responses contribute to the initiation and development of autoimmune disorders. However, the current understanding of pathogenesis is limited and the underlying mechanism has not been well defined, which lows the development of novel biomarkers and new therapeutic strategies for autoimmune diseases. To improve this, broadening and deepening our understanding of pathogenesis is an unmet need. As genetic susceptibility cannot explain the low accordance rate of incidence in homozygous twins, epigenetic regulations might be an additional explanation. Therefore, this review will summarize current progress of studies on epigenetic dysregulations contributing to autoimmune diseases, including SLE, rheumatoid arthritis (RA), psoriasis, type 1 diabetes (T1D), and systemic sclerosis (SSc), hopefully providing opinions on orientation of future research, as well as discussing the clinical utilization of potential biomarkers and therapeutic strategies for these diseases.

Aggregatibacter actinomycetemcomitans Leukotoxin (LtxA; Leukothera®): Mechanisms of Action and Therapeutic Applications

Aggregatibacter actinomycetemcomitans is an oral pathogen that produces the RTX toxin, leukotoxin (LtxA; Leukothera^®). A. actinomycetemcomitans is strongly associated with the development of localized aggressive periodontitis. LtxA acts as a virulence factor for A. actinomycetemcomitans to subvert the host immune response by binding to the β₂ integrin lymphocyte function-associated antigen-1 (LFA-1; CD11a/CD18) on white blood cells (WBCs), causing cell death. In this paper, we reviewed the state of knowledge on LtxA interaction with WBCs and the subsequent mechanisms of induced cell death. Finally, we touched on the potential therapeutic applications of LtxA (trade name Leukothera^®) toxin therapy for the treatment of hematological malignancies and immune-mediated diseases.

Epigenetics and pathogenesis of systemic sclerosis; the ins and outs

The pathogenesis of many diseases is influenced by environmental factors which can affect human genome and be inherited from generation to generation. Adverse environmental stimuli are recognized through the epigenetic regulatory complex, leading to gene expression alteration, which in turn culminates in disease outcomes. Three epigenetic regulatory mechanisms modulate the manifestation of a gene, namely DNA methylation, histone changes, and microRNAs. Both epigenetics and genetics have been implicated in the pathogenesis of systemic sclerosis (SSc) disease. Genetic inheritance rate of SSc is low and the concordance rate in both monozygotic (MZ) and dizygotic (DZ) twins is little, implying other possible pathways in SSc pathogenesis scenario. Here, we provide an extensive overview of the studies regarding different epigenetic events which may offer insights into the pathology of SSc. Furthermore, epigenetic-based interventions to treat SSc patients were discussed.

EZH2 Modulates the DNA Methylome and Controls T Cell Adhesion Through Junctional Adhesion Molecule A in Lupus Patients

OBJECTIVE

EZH2 is an epigenetic regulator that mediates H3K27 trimethylation (H3K27me3) and modulates DNA methylation. The aim of this study was to characterize the role of EZH2 in CD4+ T cells in the pathogenesis of systemic lupus erythematosus.

METHODS

EZH2 expression levels were determined in CD4+ T cells isolated from lupus patients and healthy controls. The epigenetic effects of EZH2 overexpression in CD4+ T cells were evaluated using a genome-wide DNA methylation approach. Gene expression profiles and microRNAs (miRNAs) were assessed by quantitative polymerase chain reaction, while protein expression was examined by Western blotting. A cell adhesion assay was used to assess adhesion of CD4+ T cells to human microvascular endothelial cells.

RESULTS

EZH2 and H3K27me3 levels were increased in CD4+ T cells from lupus patients compared to healthy controls. T cell production of EZH2 was down-regulated in the presence of miR-26a and miR-101, and levels of both miRNAs were reduced in lupus CD4+ T cells. Overexpression of EZH2 induced in CD4+ T cells resulted in significant DNA methylation changes. Genes involved in leukocyte adhesion and migration, including F11R (which encodes junctional adhesion molecule A [JAM-A]), became hypomethylated in CD4+ T cells when EZH2 was overexpressed. Overexpression of EZH2 resulted in increases in JAM-A expression and CD4+ T cell adhesion. Preincubation of EZH2-transfected CD4+ T cells with neutralizing antibodies against JAM-A significantly blunted cell adhesion. Similarly, CD4+ T cells from lupus patients overexpressed JAM-A and adhered significantly more to endothelial cells than to T cells from healthy controls. Blocking JAM-A or EZH2 significantly reduced the capacity of lupus CD4+ T cells to adhere to endothelial cells.

CONCLUSION

The results of this study identify a novel role of EZH2 in T cell adhesion mediated by epigenetic remodeling and up-regulation of JAM-A. Blockade of EZH2 or JAM-A might have therapeutic potential by acting to reduce T cell adhesion, migration, and extravasation in patients with lupus.

Translating epigenetics into clinic: focus on lupus

Systemic lupus erythematosus (SLE) is a chronic relapsing–remitting autoimmune disease with highly heterogeneous phenotypes. Biomarkers with high sensitivity and specificity are useful for early diagnosis as well as monitoring disease activity and long-term complications. Epigenetics potentially provide novel biomarkers in autoimmune diseases. These may include DNA methylation changes in relevant lupus-prone genes or histone modifications and microRNAs to upregulate and downregulate relevant gene expression. The timing and nature of epigenetic modification provide such changes. In lupus, DNA methylation alterations in cytokine genes, such as IFN-related gene and retrovirus gene, have been found to offer biomarkers for lupus diagnosis. Histone modifications such as histone methylation and acetylation lead to transcriptional alterations of several genes such as PTPN22, LRP1B, and TNFSF70. There are varieties of microRNAs applied as lupus biomarkers, including DNMT1-related microRNAs, renal function-associated microRNAs, microRNAs involved in the immune system, and microRNAs for phenotype classification. Thus, we conclude a wide range of promising roles of epigenetic biomarkers aiding in the diagnosing and monitoring of lupus diseases and the risk of organ damage.

Adhesion molecules, mycophenolate mofetil and systemic lupus erythematosus

Mycophenolate mofetil (MMF) has been reproducibly shown to inhibit lymphocyte adhesion and penetration of endothelial cell surfaces. The mechanism is not yet elucidated. In vitro studies on the effects of MMF on cell adhesion molecules (CAM) using human umbilical vein endothelial cells (HUVEC) have shown conflicting results. Different studies have independently shown that MMF increased, decreased or had no effect on intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule (VCAM-1). Several studies suggest MMF may reduce the endothelial expression of E-selectin. Recent studies have been unable to replicate initial work, which suggested that MMF impaired glycosylation of lymphocyte CAM. The same studies concluded that MMF had no effect on the surface expression of lymphocyte CAM, but altered the binding ability of these molecules. ICAM-1/LFA-1 (lymphocyte function-associated antigen-1), VCAM-1/VLA-4 (very late antigen-4) and P-selectin/PSGL-1 (P-selectin glycoprotein ligand-1) ligand pairs are most likely to be involved. Few in vivo and no conclusive human studies have been carried out. The literature relevant to cell adhesion molecules in systemic lupus erythematosus (SLE) is reviewed in detail.

Adhesion molecules, mycophenolate mofetil and systemic lupus erythematosus

Mycophenolate mofetil (MMF) has been reproducibly shown to inhibit lymphocyte adhesion and penetration of endothelial cell surfaces. The mechanism is not yet elucidated. In vitro studies on the effects of MMF on cell adhesion molecules (CAM) using human umbilical vein endothelial cells (HUVEC) have shown conflicting results. Different studies have independently shown that MMF increased, decreased or had no effect on intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule (VCAM-1). Several studies suggest MMF may reduce the endothelial expression of E-selectin. Recent studies have been unable to replicate initial work, which suggested that MMF impaired glycosylation of lymphocyte CAM. The same studies concluded that MMF had no effect on the surface expression of lymphocyte CAM, but altered the binding ability of these molecules. ICAM-1/LFA-1 (lymphocyte function-associated antigen-1), VCAM-1/VLA-4 (very late antigen-4) and P-selectin/PSGL-1 (P-selectin glycoprotein ligand-1) ligand pairs are most likely to be involved. Few in vivo and no conclusive human studies have been carried out. The literature relevant to cell adhesion molecules in systemic lupus erythematosus (SLE) is reviewed in detail.

A correlation study on the effects of DNMT1 on methylation levels in CD4(+) T cells of SLE patients

OBJECTIVE

To study the effect of DNMT1 on CD4(+) T cells in the peripheral blood of systemic lupus erythematosus (SLE) patients.

METHODS

To investigate the differential expression of DNMT1 in CD4(+) T cells of SLE patients and healthy individuals, a DNMT1 lentiviral plasmid (pLenti6.3/V5-DNMT1) and a control plasmid (pLenti6.3/V5-GW/LacZ) were constructed and transfected into CD4(+) T cells from the peripheral blood of SLE patients. The transcriptional and translational expression of DNMT1, global genomic DNA methylation, and the production of IgG antibody in the CD4(+) T cells in the peripheral blood of SLE patients were assessed using qPCR analysis, western blotting, flow cytometry, and ELISA, respectively.

RESULTS

The expression level of DNMT1 in SLE patients was significantly lower than that in normal humans. The expression of DNMT1 was found to be positively correlated with the methylation level of genomic DNA and negatively correlated with the IgG titration level. DNA sequencing results confirmed that the DNMT1 lentiviral plasmid was successfully constructed. After the CD4(+) T cells from the peripheral blood of SLE patients were transfected with the pLenti6.3/V5-DNMT1 plasmid, the transcription level of the DNMT1 gene was upregulated and abundance of DNMT1 protein significantly increased. Global genomic DNA methylation was enhanced, while the production of IgG antibody was reduced.

CONCLUSION

DNMT1 can inhibit the autoimmune response in SLE patients by reversing the abnormally low DNA methylation level in the CD4(+) T cells.

Epigenetic dysregulation in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a prototypical systemic autoimmune disease that affects multiple organs and is characterized by episodic flares and elevated morbidity. The etiology of SLE is only partly known. In this context, recent attention has been paid to the importance of environmentally induced epigenetic modifications as significant contributors to the disease pathogenesis in genetically predisposed individuals. Here we review what is currently known on the role of epigenetics in SLE, and the investigations aimed at possibly targeting epigenetic mechanisms and/or related biomarkers to improve the monitoring, management and, ultimately, the prognosis of SLE.

Lymphocytes from systemic lupus erythematosus patients display increased spreading on VCAM-1, an effect associated with active renal involvement

The mechanisms underlying leukocyte recruitment in systemic lupus erythematosus (SLE) are unclear. Leukocytes from SLE patients display increased integrin expression, but whether this results in an increased capacity to undergo adhesive interactions has not been investigated. Therefore, the aim of this study was to identify alterations in the capacity of leukocytes from SLE patients to undergo interactions with various substrates under flow conditions. Blood from SLE patients was examined in a flow chamber assay, and rolling, adhesion and post-adhesion spreading assessed on platelet monolayers or VCAM-1. P-selectin-dependent neutrophil rolling on platelet monolayers did not differ between SLE patients and healthy controls. Similarly, lymphocyte adhesion on VCAM-1 did not differ between patients and controls. However, post-adhesion spreading on VCAM-1 was significantly increased in lymphocytes from SLE patients. These parameters were unaffected by overall disease activity, presence of organ damage or prednisolone usage. However, leukocyte spreading on VCAM-1 was elevated in patients with evidence of active renal disease. These findings indicate that lymphocytes from SLE patients have an increased propensity to undergo post-adhesion spreading, a key preliminary step in leukocyte transmigration. This behavior may contribute to lymphocyte infiltration in SLE patients and may represent a novel biomarker of lupus nephritis.

Epigenetic code and self-identity

Epigenetics is a new and expanding science that studies the chromatin-based regulation of gene expression. It is achieving considerable importance, especially with regard to developmental mechanisms that drive cell and organ differentiation, as well as in all those biological processes that involve response and adaptation to environmental stimuli. One of the most interesting biological questions concerning animals, especially human beings, is the ability to distinguish self from nonself. This ability has developed throughout evolution, both as the main function of the immune system, which defends against attack by foreign organisms and at the level of consciousness of oneself as an individual, one of the highest functions of the brain that enables social life. Here we will attempt to dissect the epigenetic mechanisms involved in establishing these higher functions and describe some alterations of the epigenetic machinery responsible for the impairment of correct self-recognition and self-identity.

Epigenetics in systemic lupus erythematosus: leading the way for specific therapeutic agents

Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder of an unclearly determined etiology. Past studies, both epidemiological and biological, have implicated epigenetic influences in disease etiology and pathogenesis. Epigenetics describes changes in gene expression not linked to alterations in the underlying genomic sequence, and is most often typified by three modifications: methylation of DNA, addition of various side chains to histone groups and transcriptional regulation via short ncRNA sequences. The purpose of this article is to review the most important advances that link epigenetic changes to lupus. The contribution of DNA methylation changes to lupus pathogenesis is discussed. These include the role of apoptotic DNA, ultraviolet radiation, endogenous retroviruses, dietary contributions and aging. Hypomethylation of specific genes overexpressed in lupus T cells such as ITGAL (CD11a), CD40LG (CD40L), TNFSF7 (CD70), KIR2DL4 and PRF1 (perforin), and CD5 in lupus B cells seem to play an important role. Moreover, histone modifications such as increased global H4 acetylation in monocytes are highly associated with SLE. NcRNAs, especially miR-21, miR-148a and miR-126, control other elements of epigenetic regulation; particularly, transcription of the maintenance DNA methylation enzyme DNMT1. Epigenetic contributions to SLE etiology have been well established, but much is still unknown. Epigenome-wide studies coupled with functional analysis of the epigenomic changes discovered will uncover novel pathways important in disease pathogenesis. Epigenetic therapies for SLE may be feasible in the future, particularly if they are designed to target specific regions within the genome.

Association study of ITGAM, ITGAX, and CD58 autoimmune risk loci in systemic sclerosis: results from 2 large European Caucasian cohorts

OBJECTIVE

Accumulating evidence shows that shared autoimmunity is critical for the pathogenesis of many autoimmune diseases. Systemic sclerosis (SSc) belongs to the connective tissue disorders, and recent data have highlighted strong associations with autoimmunity genes shared with other autoimmune diseases. To determine whether novel risk loci associated with systemic lupus erythematosus or multiple sclerosis may confer susceptibility to SSc, we tested single-nucleotide polymorphisms (SNP) from ITGAM, ITGAX, and CD58 for associations.

METHODS

SNP harboring associations with autoimmune diseases, ITGAM rs9937837, ITGAX rs11574637, and CD58 rs12044852, were genotyped in 2 independent cohorts of European Caucasian ancestry: 1031 SSc patients and 1014 controls from France and 1038 SSc patients and 691 controls from the USA, providing a combined study population of 3774 individuals. ITGAM rs1143679 was additionally genotyped in the French cohort.

RESULTS

The 4 polymorphisms were in Hardy-Weinberg equilibrium in the 2 control populations, and allelic frequencies were similar to those expected in European Caucasian populations. Allelic and genotypic frequencies for these 3 SNP were found to be statistically similar in SSc patients and controls. Subphenotype analyses for subgroups having diffuse cutaneous subtype disease, specific autoantibodies, or fibrosing alveolitis did not reveal any difference between SSc patients and controls.

CONCLUSION

These results obtained through 2 large cohorts of SSc patients of European Caucasian ancestry do not support the implication of ITGAM, ITGAX, and CD58 genes in the genetic susceptibility of SSc, although they were recently identified as autoimmune disease risk genes.

IFN-α production by plasmacytoid dendritic cells stimulated with RNA-containing immune complexes is promoted by NK cells via MIP-1β and LFA-1

Several systemic autoimmune diseases display a prominent IFN signature. This is caused by a continuous IFN-α production by plasmacytoid dendritic cells (pDCs), which are activated by immune complexes (ICs) containing nucleic acid. The IFN-α production by pDCs stimulated with RNA-containing IC (RNA-IC) consisting of anti-RNP autoantibodies and U1 small nuclear ribonucleoprotein particles was recently shown to be inhibited by monocytes, but enhanced by NK cells. The inhibitory effect of monocytes was mediated by TNF-α, PGE(2), and reactive oxygen species, but the mechanisms for the NK cell-mediated increase in IFN-α production remained unclear. In this study, we investigated the mechanisms whereby NK cells increase the RNA-IC-induced IFN-α production by pDCs. Furthermore, NK cells from patients with systemic lupus erythematosus (SLE) were evaluated for their capacity to promote IFN-α production. We found that CD56(dim) NK cells could increase IFN-α production >1000-fold after RNA-IC activation, whereas CD56(bright) NK cells required costimulation by IL-12 and IL-18 to promote IFN-α production. NK cells produced MIP-1α, MIP-1β, RANTES, IFN-γ, and TNF-α via RNA-IC-mediated FcγRIIIA activation. The IFN-α production in pDCs was promoted by NK cells via MIP-1β secretion and LFA-mediated cell-cell contact. Moreover, NK cells from SLE patients displayed a reduced capacity to promote the RNA-IC-induced IFN-α production, which could be restored by exogenous IL-12 and IL-18. Thus, different molecular mechanisms can mediate the NK cell-dependent increase in IFN-α production by RNA-IC-stimulated pDCs, and our study suggests that the possibility to therapeutically target the NK-pDC axis in IFN-α-driven autoimmune diseases such as SLE should be investigated.

Epigenetic mechanisms of regulation of Foxp3 expression

Regulatory T cells play important roles in the control of autoimmunity and maintenance of transplantation tolerance. Foxp3, a member of the forkhead/winged-helix family of transcription factors, acts as the master regulator for regulatory T-cell (Treg) development and function. Mutation of the Foxp3 gene causes the scurfy phenotype in mouse and IPEX syndrome (immune dysfunction, polyendocrinopathy, enteropathy, X-linked syndrome) in humans. Epigenetics is defined by regulation of gene expression without altering nucleotide sequence in the genome. Several epigenetic markers, such as histone acetylation and methylation, and cytosine residue methylation in CpG dinucleotides, have been reported at the Foxp3 locus. In particular, CpG dinucleotides at the Foxp3 locus are methylated in naive CD4+CD25- T cells, activated CD4+ T cells, and TGF-beta-induced adaptive Tregs, whereas they are completely demethylated in natural Tregs. The DNA methyltransferases DNMT1 and DNMT3b are associated with the Foxp3 locus in CD4+ T cells. Methylation of CpG residues represses Foxp3 expression, whereas complete demethylation is required for stable Foxp3 expression. In this review, we discuss how different cis-regulatory elements at the Foxp3 locus are subjected to epigenetic modification in different subsets of CD4+ T cells and regulate Foxp3 expression, and how these mechanisms can be exploited to generate efficiently large numbers of suppressive Tregs for therapeutic purposes.

T cell abnormalities in systemic lupus erythematosus

Because of the consensus that T cells play a central role in the pathogenesis of systemic lupus erythematosus (SLE), we explored the molecular basis of the defective function of SLE T cells for expression of signal transduction molecules, as well as surface structures such as adhesion molecules, by extensively testing peripheral blood T cells from SLE patients. Upregulated expression and function of adhesion molecules was observed in T cells from patients with active SLE who had specific clinical manifestations such as vasculitis, epithelitis and arthritis, but proximal signal transduction was defective. Comprehensive analysis to identify the molecules responsible for the defects showed the expression of the TCR zeta chain was attenuated, or absent in more than half of SLE patients. Moreover, the aberrant transcripts of the TCR zeta chain, including spliced variants lacking exon 7 and with a short 3' UTR, were detected in SLE T cells. Although attenuated expression of the TCR zeta chain is also observed in patients with cancers, infections and other autoimmune diseases, sustained attenuation of TCR zeta expression and aberrant transcripts are only observed in SLE. In this review we discuss the unique features of the TCR zeta defects in SLE.

Hemostatic changes in vasculitides

The systemic vasculitides are an heterogeneous group of rare diseases characterized by inflammation and fibrinoid necrosis of blood vessel walls. Today it is well known that the inflammatory process characterizing vasculitides activates coagulation factors, inhibits anticoagulant factors, inhibits fibrinolytic processes, increases platelet activity and production and determines endothelial dysfunction. So far the mortality in vasculitides, even if falling, remains substantially high. Patients with vasculitic syndrome are at increased risk of developing atherosclerosis and in these patients prevalence of cardiovascular disease and cardiovascular events is higher than in the general population. Vasculitides can be associated with antiphospholipid syndrome. It is important to establish a strategy of antithrombotic therapy management in vasculitic patients, but this has not yet been clearly achieved.

Epigenetics and dermatological disease

Epigenetics is the study of differences in phenotype, in the absence of variation in the genetic code. Epigenetics is relevant in the pathogenesis of many skin diseases. In the case of the common skin cancers, aberrant methylation of tumor suppressor gene promoters is associated with their transcriptional inactivation. Environmental carcinogens such as ultraviolet radiation and arsenic may act through epigenetic mechanisms. Hypomethylation is associated with activation of systemic autoimmune diseases, such as systemic lupus erythematosus, subacute cutaneous lupus erythematosus and scleroderma. This may be through a mechanism of immunological cross-reactivity with hypomethylated DNA from pathogenic bacteria. Epigenetic factors may also be relevant in the pathogenesis of psoriasis and other inflammatory skin diseases, as well as in the pathogenesis of the disorders of genomic imprinting with cutaneous features.

Epigenetic connections between autoimmune disorders and haematological malignancies

Epigenetic deregulation has become a major topic in biomedical research. Most of the information currently available in the field comes from the study of epigenetic alterations in cancer, particularly in haematological malignancies. The recognition of the epigenetic component of autoimmune diseases in conjunction with the existence of common genes underpinning pathways that are crucial to the development of autoimmunity and haematological cancers, facilitates interaction between these two areas of research. Here, we examine what is presently known from epigenetic studies of autoimmune diseases, how epigenetic alterations in haematological malignancies can be used to better understand mechanisms of epigenetic deregulation and how they might be used in epigenetic therapy to treat autoimmune diseases.

Transcript levels of DNA methyltransferases DNMT1, DNMT3A and DNMT3B in CD4+ T cells from patients with systemic lupus erythematosus

Global DNA hypomethylation in CD4(+) T cells has been detected in systemic lupus erythematosus (SLE) and it seems to be linked to its pathogenesis. We investigated the relationship between overall DNA methylation and the expression of three DNA (cytosine-5) methyltransferases involved in the DNA methylation process. The DNA deoxymethylcytosine (dmC) content of purified CD4(+) T cells from 29 SLE patients and 30 healthy controls was measured by means of an enzyme-linked immunosorbent assay (ELISA). The transcript levels of DNA cytosine-5-methyltransferase 1 (DNMT1), DNA cytosine-5-methyltransferase 3A (DNMT3A) and DNA cytosine-5-methyltransferase 3B (DNMT3B) were quantified by real-time reverse transcription-polymerase chain reaction (RT-PCR). Association studies were also carried out with several laboratory parameters, as well as with the patients' clinical manifestations. SLE patients had a significantly lower CD4(+) T-cell DNA dmC content than controls (0.802 +/- 0.134 versus 0.901 +/- 0.133) (P = 0.007). No differences in transcript levels were observed for DNMT1, DNMT3A and DNMT3B between patients and controls. The simultaneous association of low complement counts with lymphopenia, high titres of anti-double-stranded DNA (anti-dsDNA), or an SLE disease activity index (SLEDAI) of > 5, resulted in the increase of at least one of the three DNA methyltransferases. It is possible that patients were reacting indirectly to an underlying DNA hypomethylation status by increasing the mRNA levels of DNA methyltransferases when the disease was being definitely active.

Differential roles of ICAM-1 and VCAM-1 in leukocyte-endothelial cell interactions in skin and brain of MRL/faslpr mice

MRL/fas(lpr) mice, which undergo a systemic autoimmune disease with similarities to systemic lupus erythematosus (SLE), display reduced pathology and prolonged survival if rendered deficient in ICAM-1. However, it remains unclear whether this is a result of the ability of ICAM-1 to promote the immune response or mediate leukocyte recruitment. Therefore, the aim of these studies was to compare the role of ICAM-1 in the elevated leukocyte-endothelial interactions, which affect MRL/fas(lpr) mice. Intravital microscopy was used to compare leukocyte rolling and adhesion in postcapillary venules in the dermal and cerebral (pial) microcirculations of wild-type (ICAM+/+) and ICAM-1-deficient (ICAM-1-/-) MRL/fas(lpr) mice. In the dermal microcirculation of 16-week MRL/fas(lpr) mice, leukocyte adhesion was increased relative to nondiseased MRL+/+ mice. However, this increase was abolished in ICAM-1-/- MRL/fas(lpr) mice. ICAM-1 deficiency was also associated with reduced dermal pathology. In contrast, in the pial microcirculation, the elevation in leukocyte adhesion observed in ICAM+/+ MRL/fas(lpr) mice also occurred in ICAM-1-/- MRL/fas(lpr) mice. VCAM-1 expression was detectable in both vascular beds, but higher levels were detected in the pial vasculature. Furthermore, VCAM-1 blockade significantly reduced leukocyte adhesion and rolling in the cerebral microcirculation of ICAM-1-/- MRL/fas(lpr) mice. Therefore, ICAM-1 was critical for leukocyte adhesion in the skin but not the brain, where VCAM-1 assumed the major function. Given the ongoing development of anti-adhesion molecule therapies and their potential in inflammatory diseases such as SLE, these data indicate that implementation of these therapies in SLE should take into account the potential for tissue-specific functions of adhesion molecules.

DNA methylation and systemic lupus erythematosus

Several studies have indicated the importance of DNA hypomethylation in the etiology of systemic lupus erythematosus (SLE). Different enzymes linked to the DNA methylation process have been described. The identification of all these enzymes means that cells have the capacity to modify their methylation patterns. Therefore, to obtain a deeper understanding of the role this epigenetic mechanism may have on SLE, the enzymes involved in the DNA methylation mechanism must be thoughtfully analyzed. In fact, studies of enzymes (other than DNMT1) in this autoimmune disease are still lacking. We have recently investigated the simultaneous gene expression of DNMT1, DNMT3A, DNMT3B, MBD2, and MBD4 in SLE patients. Here we review some of the studies that focus on the relationship between DNA methylation and SLE as well as we report our recent findings in this field. We suggest some alternative hypothesis that could help to understand the causes of the global DNA hypomethylation observed in the CD4+ T cells of these patients.

Activation signal transduction by beta1 integrin in T cells from patients with systemic lupus erythematosus

OBJECTIVE

Beta 1 integrin is a representative adhesion molecule for cell-cell and cell-extracellular matrix interactions, and it provides costimulatory signals to T cells. However, the relevance of beta1 integrin to T cell activation in systemic lupus erythematosus (SLE) remains unclear. We undertook this study to perform a quantitative and functional analysis of beta1 integrin-mediated signaling to T cells in patients with SLE.

METHODS

Expression of cell surface molecules was assessed by flow cytometric analysis. Engagement of beta1 integrins was performed by crosslinking using a specific monoclonal antibody. To assess tyrosine kinases in beta1 integrin-mediated signaling, the cells were transfected with a wild-type (WT) focal adhesion kinase (FAK), a dominant-negative truncation of the FAK, or a WT PTEN expression plasmid via nucleofection.

RESULTS

Beta 1 integrin expression was significantly up-regulated on peripheral blood T cells from patients with active SLE, particularly those with the complication of World Health Organization class IV nephritis, whereas CD28 was significantly decreased in patients with active SLE compared with normal individuals. Beta 1 integrin expression closely correlated with serum hypocomplementemia. Engagement of beta1 integrin on T cells from patients with active SLE, but not on those from normal individuals, induced cell proliferation as well as CD40L expression on T cells. Up-regulation of CD40L expression and T cell proliferation, induced by beta1 integrin stimulation, were completely inhibited by transfection of the dominant-negative truncations of FAK or WT PTEN.

CONCLUSION

These results suggest that engagement of beta1 integrins on SLE T cells could induce FAK-mediated signaling and subsequent CD40L expression and proliferation. Thus, the beta1 integrin signaling cascade might serve to enhance autoreactive T cell activation.

Phosphorylated ERM is responsible for increased T cell polarization, adhesion, and migration in patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune/inflammatory disease characterized by autoantibody production and abnormal T cells that infiltrate tissues through not well-known mechanisms. We report that SLE T lymphocytes display increased levels of CD44, ezrin, radixin, and moesin (ERM) phosphorylation, stronger actin polymerization, higher polar cap formation, and enhanced adhesion and chemotactic migration compared with T cells from patients with rheumatoid arthritis and normal individuals. Silencing of CD44 by CD44 small interfering RNA in SLE T cells inhibited significantly their ability to adhere and migrate as did treatment with Rho kinase and actin polymerization inhibitors. Forced expression of T567D-ezrin, a phosphorylation-mimic form, enhanced remarkably the adhesion and migration rate of normal T cells. Anti-CD3/TCR autoantibodies present in SLE sera caused increased ERM phosphorylation, adhesion, and migration in normal T cells. pERM and CD44 are highly expressed in T cells infiltrating in the kidneys of patients with lupus nephritis. These data prove that increased ERM phosphorylation represents a key molecular abnormality that guides T cell adhesion and migration in SLE patients.

Transcript overexpression of the MBD2 and MBD4 genes in CD4+ T cells from systemic lupus erythematosus patients

Global DNA hypomethylation in CD4+ T cells has been detected in systemic lupus erythematosus (SLE), and it seems to be linked to its pathogenesis. We investigated the relationship between overall DNA methylation and the expression of two methyl CpG-binding domain (MBD) proteins. DNA deoxymethylcytosine (d(m)C) content of purified CD4(+) T cells from 29 SLE patients and 30 healthy controls was measured by means of an ELISA. Transcript levels of two methyl CpG-binding proteins (MBD2 and MBD4) were quantified by real-time RT-PCR. Association studies were also carried out with several laboratory parameters, as well as with the patients' clinical manifestations. SLE patients had significantly less CD4+ T cell DNA d(m)C content than controls (0.802+/-0.134 vs. 0.901+/-0.133; P=0.007). MBD2 and MBD4 mRNA levels were considerably higher in the patients' group: 0.975 +/- 0683 versus 0.604 +/- 0.614 (P=0.004) and 0.359 +/- 0.330 versus 0.092 +/- 0.169, respectively (P<0.0005). It is interesting that SLE patients showed a negative correlation between methylation indices and MBD2 (r=-0.609, P<0.0005) and MBD4 (r=-0.395, P=0.034) transcript levels. MBD2 and MBD4 transcript overexpression and inverse correlations with DNA methylation indices indicate that both enzymes may really have a direct and active role on the genome-wide DNA hypomethylation observed in CD4+ T cells from SLE patients.

TCRzeta mRNA splice variant forms observed in the peripheral blood T cells from systemic lupus erythematosus patients

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease of unknown etiology. Tyrosine phosphorylation and protein expression of the T-cell receptor zeta chain (zeta) have been reported to be significantly decreased in SLE T cells. In addition, zeta mRNA with alternatively spliced 3' untranslated region (zetamRNA/as-3'UTR) is detected predominantly in SLE T cells, and aberrant zeta mRNA accompanied by the mutations in the open reading frame including zeta mRNA lacking exon7 (zetamRNA/exon7-) is observed in SLE T cells. These zeta mRNA splice variant forms exhibit a reduction in the expression of TCR/CD3 complex and zeta protein on their cell surface due to the instability of zeta mRNA splice variant forms as well as the reduction in interleukin (IL)-2 production after stimulating with anti-CD3 antibody. Data from cDNA microarray showed that 36 genes encoding cytokines and chemokines, including IL-2, IL-15, IL-18, and TGF-beta2, were down-regulated in the MA5.8 cells transfected with the zeta mRNA splice variant forms. Another 16 genes were up-regulated and included genes associated with membranous proteins and cell damage granules, including the genes encoding poliovirus-receptor-related 2, syndecan-1, and granzyme A.

The epigenetic face of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an archetypical systemic, autoimmune inflammatory disease characterized by the production of autoantibodies to multiple nuclear Ags. Apoptotic defects and impaired removal of apoptotic cells contribute to an overload of autoantigens that become available to initiate an autoimmune response. Besides the well-recognized genetic susceptibility to SLE, epigenetic factors are important in the onset of the disease, as even monozygotic twins are usually discordant for the disease. Changes in DNA methylation and histone modifications, the major epigenetic marks, are a hallmark in genes that undergo epigenetic deregulation in disease. In SLE, global and gene-specific DNA methylation changes have been demonstrated to occur. Moreover, histone deacetylase inhibitors reverse the skewed expression of multiple genes involved in SLE. In the present study, we discuss the implications of epigenetic alterations in the development and progression of SLE and how epigenetic drugs constitute a promising source of therapy to treat this disease.

The inhibition of autoreactive T cell functions by a peptide based on the CDR1 of an anti-DNA autoantibody is via TGF-beta-mediated suppression of LFA-1 and CD44 expression and function

Systemic lupus erythematosus (SLE), which is characterized by the increased production of autoantibodies and defective T cell responses, can be induced in mice by immunization with a human anti-DNA mAb that expresses a major Id, designated 16/6Id. A peptide based on the sequence of the CDR1 of the 16/6Id (human CDR1 (hCDR1)) ameliorated the clinical manifestations of SLE and down-regulated, ex vivo, the 16/6Id-induced T cell proliferation. In this study, we examined the mechanism responsible for the hCDR1-induced modulation of T cell functions related to the pathogenesis of SLE. We found that injection of hCDR1 into BALB/c mice concomitant with their immunization with 16/6Id resulted in a marked elevation of TGF-beta secretion 10 days later. Addition of TGF-beta suppressed the 16/6Id-stimulated T cell proliferation similarly to hCDR1. In addition, we provide evidence that one possible mechanism underlying the hCDR1- and TGFbeta-induced inhibition of T cell proliferation is by down-regulating the expression, and therefore the functions, of a pair of key cell adhesion receptors, LFA-1 (alphaLbeta2) and CD44, which operate as accessory molecules in mediating APC-T cell interactions. Indeed, T cells of mice treated with hCDR1 showed a TGF-beta-induced suppression of adhesion to the LFA-1 and CD44 ligands, hyaluronic acid and ICAM-1, respectively, induced by stromal cell-derived factor-1alpha and PMA. The latter suppression is through the inhibition of ERK phosphorylation. Thus, the down-regulation of SLE-associated responses by hCDR1 treatment may be due to the effect of the up-regulated TGF-beta on the expression and function of T cell adhesion receptors and, consequently, on T cell stimulation, adhesion, and proliferation.

Mechanisms of lymphocyte migration in autoimmune disease

The recruitment of leukocytes to inflamed tissues plays an essential role in combating infection and promoting wound healing. However, in autoimmune diseases such as multiple sclerosis and diabetes, leukocytes enter tissues and contribute to inappropriate inflammatory responses, which cause tissue injury and dysfunction. In diseases of this type, lymphocytes play critical roles in initiating and maintaining these aberrant inflammatory responses. The aim of this review is to examine the mechanisms whereby T-lymphocytes enter tissues in autoimmune diseases and to compare these mechanisms between various organs and diseases. An overview of the mechanisms of leukocyte recruitment and the techniques used to study leukocyte trafficking is provided, focusing on the use of intravital microscopy as a tool to assess the functional microvasculature in vivo. We also discuss the series of tissue homing events which allow naïve lymphocytes to first enter lymph nodes and undergo activation, then subsequently to home to the peripheral organ where their cognate antigen is present. Finally, we examine mechanisms of leukocyte recruitment in diseases such as multiple sclerosis, autoimmune diabetes, systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease and asthma.

Decreased T cell ERK pathway signaling may contribute to the development of lupus through effects on DNA methylation and gene expression

T cells from patients with active lupus have multiple biochemical abnormalities. One of these is DNA hypomethylation, which in model systems alters gene expression and induces lupus-like autoimmunity. Recent reports indicate that DNA methylation is regulated in part by the ERK pathway, and that ERK pathway signaling is diminished in lupus T cells. This suggests a model in which defective T cell ERK pathway signaling contributes to the development of autoimmunity by decreasing DNA methyltransferase expression, modifying DNA methylation patterns and altering gene expression. This mechanism could contribute to idiopathic and drug-induced lupus.

Altered expression of the T cell receptor-CD3 complex in systemic lupus erythematosus

SLE T cells may play a key role in autoantibody production in SLE B cells. In addition, accumulating evidence has shown that SLE T cells participate in the attack on target cells or tissues through the overproduction of pro-inflammatory cytokines or an increase in cell-to-cell adhesion. Thus, the functional abnormality of SLE T cells appears to be pivotal to an understanding of SLE pathogenesis. Accumulating evidence suggests that potential defects may reside in the proximal signal transduction around the TCR-CD3 complex. We have demonstrated that the expression of TCR zeta chain is significantly decreased in peripheral blood T cells from SLE patients. To explore the mechanism of defective expression of TCR zeta chain, we examined mRNA of TCR zeta, and found that two alternatively spliced variants such as exon 7 (-) and short 3'-UTR are detected in SLE. We review the possible role of the TCR zeta defects in autoimmunity and discuss how the splicing variants lead to downregulated protein expression of TCR zeta chain.

Loss of LFA-1, but not Mac-1, protects MRL/MpJ-Fas(lpr) mice from autoimmune disease

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by immune complex-mediated tissue injury. Many different adhesion molecules are thought to participate in the development of SLE; however, few studies have directly examined the contributions of these proteins. Here we demonstrate that LFA-1 plays an essential role in the development of lupus in MRL/MpJ-Fas(lpr) mice. Mice deficient in LFA-1, but not Mac-1, showed significantly increased survival, decreased anti-DNA autoantibody formation, and reduced glomerulonephritis. The phenotype of the LFA-1-deficient mice was similar to that observed in beta(2) integrin-deficient (CD18-null) MRL/MpJ-Fas(lpr) mice, suggesting a lack of redundancy among the beta(2) integrin family members and other adhesion molecules. These studies identify LFA-1 as a key contributor in the pathogenesis of autoimmune disease in this model, and further suggest that therapeutic strategies targeting this adhesion molecule may be beneficial for the treatment of SLE.

DNA methylation and autoimmune disease

DNA methylation plays an essential role in maintaining T-cell function. A growing body of literature indicates that failure to maintain DNA methylation levels and patterns in mature T cells can result in T-cell autoreactivity in vitro and autoimmunity in vivo. Defective maintenance of DNA methylation may be caused by drugs such as procainamide or hydralazine, or failure to activate the genes encoding maintenance DNA methyltransferases during mitosis, resulting in the development of a lupus-like disease or perhaps other autoimmune disorders. This paper reviews the evidence supporting a role for abnormal T-cell DNA methylation in causing autoimmunity in an animal model of drug-induced lupus, and discusses some of the mechanisms involved. T cells from patients with active lupus have evidence for most if not all of the same methylation abnormalities, suggesting that abnormal DNA methylation plays a role in idiopathic human lupus as well.

T Cell Integrin Overexpression as a Model of Murine Autoimmunity

Integrin adhesion molecules have important adhesion and signaling functions. They also play a central role in the pathogenesis of many autoimmune diseases. Over the past few years we have described a T cell adoptive transfer model to investigate the role of T cell integrin adhesion molecules in the development of autoimmunity. This report summarizes the methods we used in establishing this murine model. By treating murine CD4+ T cells with DNA hypomethylating agents and by transfection we were able to test the in vitro effects of integrin overexpression on T cell autoreactive proliferation, cytotoxicity, adhesion and trafficking. Furthermore, we showed that the ability to induce in vivo autoimmunity may be unique to the integrin lymphocyte function associated antigen-1 (LFA-1).

Is macrophage migration inhibitory factor a therapeutic target in systemic lupus erythematosus?

Systemic lupus erythematosus (SLE) is the prototype of a cluster of diseases that are characterized by a loss of self tolerance and chronic inflammation in organs including skin, kidney, brain and joints. Researchers have long debated the varying contributions of the components of the immune system to the pathogenesis of SLE, but the emigration of leucocytes from the microcirculation, and the subsequent tissue inflammation mediated by these inflammatory cells, are key features of chronic inflammation seen in SLE. Macrophage migration inhibitory factor (MIF) is a broad-spectrum pro-inflammatory cytokine. We hypothesize that MIF is an important inflammatory mediator in the perpetuation of immune activation in SLE, via its effects on activation of T and B cells, and endothelial and effector cells. As MIF exerts anti-apoptotic effects, it may also play a role in promoting abnormal survival of autoreactive lymphocytes, thus perpetuating autoimmune reactivity. In addition, MIF has a unique relationship with glucocorticoids, in that MIF can override the effects of glucocorticoids and may be important in steroid resistance. By virtue of its pluripotent functions, we propose that MIF may be a critical mediator of inflammation and damage in SLE, and that targeting of MIF may offer therapeutic benefits in this disease.

Alterations in leucocyte trafficking in lupus-prone mice: an examination of the MRL/faslpr mouse

Systemic lupus erythematosus (SLE) is an autoimmune disease involving inappropriate inflammatory responses in a wide range of organs. The recruitment of leucocytes to these sites of inflammation is one of the key events in the development of tissue injury in SLE. However, the mechanisms responsible for this aberrant recruitment are poorly understood. Several studies have demonstrated upregulation of endothelial adhesion molecule expression in tissue biopsies from SLE patients. However, the progression to analysis of the functional roles of these adhesion molecules has entailed the use of animal models of SLE. Much of this work has involved the use of the MRL/faslpr mouse model of systemic autoimmune disease. This mouse develops a systemic inflammatory disease with similarities to human SLE. This review summarizes work by our laboratory and others which have examined alterations in the mechanisms of leucocyte trafficking in the MRL/faslpr mouse. These experiments have revealed upregulation of key adhesion molecules, alterations in leucocyte-endothelial cell interactions and in some cases protective effects of deletion of endothelial adhesion molecules. From analysis of a range of microvasculatures in the MRL/faslpr mouse, it is becoming clear that the roles of specific adhesion molecules vary according to the tissue under analysis. Furthermore, analysis of MRL/faslpr mice with targeted deletions of specific adhesion molecules indicates that their roles in development and progression of disease can vary from having key contributions to the development of disease, to attenuating disease via as yet unidentified mechanisms.

T cell abnormalities in human and mouse lupus: intrinsic and extrinsic

The purpose of this review is to discuss recent developments in the biology and biochemistry of the T cells in mice and humans with systemic lupus erythematosus. T cells that recognize self-antigens are present in systemic lupus erythematosus and normal organisms. It is obvious, though, that an autoimmune environment should be present to disrupt anergy and instigate a response that might cause disease. The environment that lifts anergy is defined by distinct molecular aberrations that include rewiring of the T cells. Aberrant transcription of genes that encode proteins involved in autoimmunity can be traced to abnormal expression and activation of transcription factors and promoter methylation intensity. Only certain components of the autoimmune response can be linked to pathologic changes in the target organ that might be dictated by additional local factors. The works reviewed imply that self-peptides might be considered to reestablish lost tolerance, whereas correction of the aberrant biochemistry might normalize T cell function and limit disease.

CD49d overexpression and T cell autoimmunity

D10.G4.1 (D10) cells, a murine conalbumin-reactive Th2 cell line, made to overexpress the beta(2) integrin LFA-1 by pharmacological manipulation or by transfection become autoreactive and are capable of inducing in vivo autoimmunity. However, whether this is specific to LFA-1 and whether overexpression of other T cell integrin molecules has the same effect are unknown. We examined the functional consequences of T cell CD49d (alpha(4) integrin) overexpression by transfecting murine CD49d cDNA into D10 cells. Similar to the LFA-1-transfected cells, the CD49d-overexpressing T cells are autoreactive and proliferate in response to APCs in an MHC class II-dependent manner in the absence of nominal Ag. Additionally, CD49d overexpression is associated with increased in vitro adhesion to endothelial cells and increased in vivo splenic homing. However, in contrast to LFA-1 overexpression, increased T cell CD49d expression is not associated with autoreactive cytotoxicity or the ability to induce in vivo autoimmunity. In addition to the novel observation that CD49d overexpression is sufficient to induce T cell autoreactivity, our results also support the hypothesis that the ability to induce in vivo autoimmunity is related to T cell cytotoxicity and not to T cell proliferation function in the D10 murine adoptive transfer model of autoimmunity.

Early inflammatory markers in elicitation of allergic contact dermatitis

BACKGROUND

Allergic Contact Dermatitis (ACD) is regarded as a T-cell-mediated delayed-type hypersensitivity reaction. We studied the kinetics of the expression of CS-1 fibronectin, thymus and activation-regulated chemokine (CCL17/ TARC) and different chemokine receptors (CR) in skin biopsies from individuals suffering from back problems, with the antigen responsible of their contact dermatitis and an irrelevant antigen.

METHODS

Samples were taken at 2, 10, and 48 hours for histological and immunohistochemical studies using monoclonal antibodies against human CS-1 fibronectin, CCL17, CD3, CD68, CD49d, CXCR3, CCR5, and CCR3.

RESULTS

At positive antigen stimulated sites there was an early expression of CS-1 fibronectin (2 hours), followed by CCL17 and a later accumulation of alplha4/beta1+ (CD49d), CD3+, CD68+, CXCR3+ and CCR5+ mononuclear cells. At 48 hours, approximately 59 % of infiltrating cells were CXCR3+, 42% CCR5+, and only 14 % CCR3+.

CONCLUSIONS

These results showed for the first time a very early expression of CS-1 fibronectin which preceded production of CCL17 in blood endothelial cells (BCEs) from patients' skin with ACD. The role of these molecules in recruitment of monocytes and effector T cells in ACD is discussed.

Defective expression and tyrosine phosphorylation of the T cell receptor zeta chain in peripheral blood T cells from systemic lupus erythematosus patients

We have reported that tyrosine phosphorylation and expression of the T cell receptor zeta chain (TCR zeta) was decreased in two systemic lupus erythematosus (SLE) patients with an abnormal TCR zeta lacking exon-7. To examine further the TCR zeta defect and any possible relationship with specific clinical features, we studied the expression of TCR zeta in peripheral blood T cells from 44 patients with SLE, 53 with other rheumatic diseases (30 rheumatoid arthritis (RA), 11 systemic sclerosis (SSc) and 12 primary Sjögren's syndrome(SjS)) and 39 healthy individuals. Flow cytometric analysis demonstrated a significant decrease in the expression of TCR zeta in SLE (P < 0.001), but not in the other rheumatic diseases. Immunoprecipitation experiments confirmed that the expression of TCR zeta in SLE T cells was decreased dramatically (normal: 111.4 +/- 22.6%, SLE: 51.6 +/- 37.4%, P < 0.0001). The decrease in TCR zeta did not correlate with disease activity, or with the dose of prednisolone (PSL). There were, however, three SLE patients in whom the level of TCR zeta expression normalized after treatment, suggesting that mechanisms responsible for the TCR zeta defect appear to be heterogeneous. These results confirm the defective expression and altered tyrosine phosphorylation of TCR zeta in a large proportion of SLE patients, suggesting that it may play an important role in T cell dysfunction in SLE.

Demethylation of ITGAL (CD11a) regulatory sequences in systemic lupus erythematosus

OBJECTIVE

Inhibition of T cell DNA methylation causes autoreactivity in vitro and a lupus-like disease in vivo, suggesting that T cell DNA hypomethylation may contribute to autoimmunity. The hypomethylation effects are due, in part, to overexpression of lymphocyte function-associated antigen 1 (LFA-1) (CD11a/CD18). Importantly, T cells from patients with active lupus have hypomethylated DNA and overexpress LFA-1 on an autoreactive subset, suggesting that the same mechanism could contribute to human lupus. The present study investigated the nature of the methylation change that affects LFA-1 expression in vitro and in human lupus.

METHODS

Bisulfite sequencing was used to determine the methylation status of the ITGAL promoter and flanking regions in T cells from lupus patients and healthy subjects, and in T cells treated with DNA methylation inhibitors. "Patch" methylation of promoter sequences in reporter constructs was used to determine the functional significance of the methylation changes.

RESULTS

Hypomethylation of specific sequences flanking the ITGAL promoter was seen in T cells from patients with active lupus and in T cells treated with 5-azacytidine and procainamide. Patch methylation of this region suppressed ITGAL promoter function.

CONCLUSION

DNA methylation changes occur in specific sequences that regulate LFA-1 expression in lupus T cells and in the hypomethylation model, indicating that altered methylation of specific genes may play a role in the pathogenesis of lupus.