Expression and activity analyses of CTLA4 in peripheral blood lymphocytes in systemic lupus erythematosus patients

A better understanding of the role of the CTLA-CD80/86 axis in the treatment of autoimmune diseases

Autoimmune diseases are diseases in which the regulatory mechanisms of the immune response are disturbed. As a result, the body loses self-tolerance. Since one of the main regulatory mechanisms of the immune response is the CTLA4-CD80/86 axis, this hypothesis suggests that autoimmune diseases potentially share a similar molecular basis of pathogenesis. Hence, investigating the CTLA4-CD80/86 axis may be helpful in finding an appropriate treatment strategy. Therefore, this study aims to investigate the molecular basis of the CTLA4-CD80/86 axis in the regulation of the immune response, and then its role in developing some autoimmune diseases, including systemic lupus erythematosus, rheumatoid arthritis, type 1 diabetes, and multiple sclerosis. As well, the main therapeutic strategies affecting the CTLA4-CD80/86 axis have been summarized to highlight the importance of this axis in management of autoimmune diseases.

Brief report: increased expression of a short splice variant of CTLA-4 exacerbates lupus in MRL/lpr mice

OBJECTIVE

CTLA-4 is a negative regulator of the immune response expressed by regulatory T (Treg) cells and activated T cells. Polymorphisms in the CTLA4 gene have been associated with autoimmune diseases, including systemic lupus erythematosus. Disease-associated polymorphisms have been shown to affect the production of the different CTLA-4 variants through an effect on alternative splicing. This study was undertaken to evaluate the role of the 1/4 CTLA-4 isoform in lupus-prone mice.

METHODS

We generated an MRL/lpr mouse strain that transgenically overexpresses a short isoform of CTLA-4 (1/4 CTLA-4) by backcrossing C57BL/6.1/4CTLA-4-transgenic mice to the MRL/lpr strain for 9 generations. A new antibody was generated to detect the expression of the 1/4 CTLA-4 isoform. Routine methods were used to evaluate kidney damage, humoral immunity, and cellular immunity.

RESULTS

Expression of the 1/4 CTLA-4 isoform accelerated autoimmune disease. Transgenic mice died earlier, had more severe renal disease, and had higher titers of anti-double-stranded DNA antibodies than wild-type MRL/lpr mice. The acceleration of autoimmunity and disease pathology associated with the presence of the short (1/4) isoform of CTLA-4 was linked to increased numbers of activated T cells and B cells and heightened interferon-γ production, but not to altered expression of the full-length CTLA-4 molecule or Treg cell numbers.

CONCLUSION

Our results indicate that the presence of the alternatively spliced 1/4 CTLA-4 isoform can further promote autoimmunity and autoimmune pathology in lupus-prone mice and suggest that altered splicing of CTLA4 contributes to the expression of autoimmune disease.

Characterization of the metabolic phenotype of chronically activated lymphocytes

Activated lymphocytes proliferate, secrete cytokines, and can make antibodies. Normally activated B and T cells meet the bioenergetic demand for these processes by up-regulating aerobic glycolysis. In contrast, several lines of evidence suggest that pathogenic lymphocytes in autoimmune diseases like lupus meet ATP demands through oxidative phosphorylation. Using (13)C-glucose as a stable tracer, we found that splenocytes from mice with lupus derive the same fraction of lactate from glucose as control animals, suggesting comparable levels of glycolysis and non-oxidative ATP production. However, lupus splenocytes increase glucose oxidation by 40% over healthy control animals. The ratio between pentose phosphate cycle (PPC) activity and glycolysis is the same for each group, indicating that increased glucose oxidation is due to increased activity of the TCA cycle in lupus splenocytes. Repetitive stimulation of cultured human T cells was used to model chronic lymphocyte activation, a phenotype associated with lupus. Chronically activated T cells rely primarily on oxidative metabolism for ATP synthesis suggesting that chronic antigen stimulation may be the basis for the metabolic findings observed in lupus mice. Identification of disease-related bioenergetic phenotypes should contribute to new diagnostic and therapeutic strategies for immune diseases.

Decrease in CD4+CD25+ and CD8+CD28+ T cells in interstitial pneumonitis associated with rheumatic disease

The expression of CD25 or CD28 on T cells was examined in patients with rheumatic diseases associated with interstitial pneumonitis (IP), in order to investigate the conditions of CD4+CD25+ regulatory T cells and CD8+CD28- suppressor T cells. Fifty-five patients with various rheumatic diseases and 23 normal controls were enrolled. CD4+CD25+ T cells of patients with IP were significantly decreased in comparison with non-IP patients, and the ratio of CD8+CD28- T cells in patients with IP was significantly higher than that in non-IP patients or normal controls. These results for CD8+CD28- T cells were in accord with the decrease in CD8+CD28+ T cells, and may be related to activation-induced CD8+CD28+ T-cell death. Thus, the abnormality of CD4+CD25+ regulatory T cells may be related to the pathogenesis of IP, and the survival and activation of CD8+ T cells.

Inverse correlation between CD4+ regulatory T-cell population and autoantibody levels in paediatric patients with systemic lupus erythematosus

CD4(+) CD25(+) regulatory T cells (Tregs) are critical in maintaining self-tolerance and preventing organ-specific autoimmunity. Their role in paediatric systemic lupus erythematosus (SLE), an autoimmune disease characterized by inappropriate regulation of hyperactivated B and T cells, has not been clearly defined. Using flow cytometry to determine cell populations and real-time polymerase chain reaction to assay mRNA expression for FOXP3, CTLA-4, and GITR, we characterized CD4(+) CD25(+) T cells in paediatric SLE patients and healthy subjects. The frequency of CD4(+) CD25(+) Tregs was significantly decreased in patients with active SLE compared with patients with inactive SLE and with controls (7.27% +/- 2.50%, 9.59% +/- 2.80% and 9.78% +/- 2.11%, respectively; P = 0.027 and P < 0.001, respectively), and was inversely correlated with disease activity, as assessed with the Systemic Lupus Erythematosus Disease Activity Index 2000 scores (r = -0.59, P = 0.001) and serum anti-double-stranded DNA levels (r = -0.65, P < 0.001). Our preliminary investigations found elevated surface expression of GITR in CD4(+) CD25(+) T cells, elevated mRNA expression of CTLA-4 in CD4(+) T cells and higher amounts of mRNA expression for FOXP3 in CD4(+) cells in patients with active SLE compared with patients with inactive disease and controls. We demonstrated reduced CD4(+) CD25(+) Treg levels were inversely correlated with disease activity, indicating a defective Treg population in paediatric SLE patients. The differences in the expression of FOXP3, CTLA-4 and GITR imply the possible role of CD4(+) Tregs in the pathogenesis of SLE.

Lupus eritematoso sistémico pediátrico

Pediatric systemic lupus erythematosus (pSLE) is a chronic mutisystemic autoimmune disease with complex clinical manifestations. Although the presentation, clinical manifestations, immunological findings and treatment issues of pSLE are similar to those of adult SLE patients, there are special issues which need to be considered when dealing with SLE in children. During the last decade survival has improved remarkably as a result of earlier diagnosis, recognition of milder disease and better approaches to therapy. However, pSLE remains a potentially serious condition. Although the pathogenesis of SLE remains poorly understood, susceptibility involves a combination of environmental, hormonal and genetic factors. Better understanding of SLE pathogenesis will hopefully lead to more specific and less toxic therapies for this disease.

Increase of activated T-cells and up-regulation of Smad7 without elevation of TGF-beta expression in tonsils from patients with pustulosis palmaris et plantaris

Pustulosis palmaris et plantaris (PPP) is known to be a skin disease related to tonsillitis, because the pustulosis often become exacerbated during acute tonsillitis and disappears after tonsillectomy. However, etiology of PPP remains unclear. In this study, we investigated the activation of tonsillar T-cell from PPP patients. Furthermore, we analyzed expressions of cytotoxic T-lymphocyte antigen-4 (CTLA4) that is a co-stimulatory molecule for inhibition of T-cell activation and of Smad7 that is a regulatory factor of TGF-beta intracellular signaling. For 47 Japanese patients with PPP who had tonsillectomy, the skin lesion was improved in 87% of PPP patient at 12 months after tonsillectomy. In quantitative immunohistologic analysis, T-cell nodules on tonsillar tissues from PPP patients were more expanded than those from the patients with obstructive sleep apnea syndrome (OSAS) (P = 0.015), and there was a positive correlation between the enlargement and clinical improvement (r = 0.422, P = 0.021). Flow cytometric analysis showed that the numbers of CD4+CD25+ and CD4+CD29+ cells in tonsils from PPP patients increased significantly compared to those from OSAS patients (P = 0.017, P = 0.016, respectively). Using reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting analyses with CD3+ tonsillar lymphocytes, we found that both expressions of Smad7 mRNA and protein were enhanced in PPP patients compared with OSAS patients (P = 0.03, P = 0.02, respectively), but expression of TGF-beta mRNA was not different between 2 groups. Although mRNA expression of CTLA4 was reduced in PPP patients compared with OSAS patients (P = 0.04), the CTLA4 surface protein expression was not different between 2 groups. These data suggest that helper T-cells are frequently activated in tonsils from PPP patients, and this activation may be related to unresponsiveness of TGF-beta1 by overexpression of Smad7. Such hyper-activation of T-cell may increase the risk of elicitation of self-reactive T-cell, being associated with pathogenesis of PPP.

Systemic lupus erythematosus trials: successes and issues

PURPOSE OF REVIEW

The purpose of this review is to discuss the most recent published clinical trials for systemic lupus erythematosus and to identify important issues that have arisen in association with the search for new therapies for systemic lupus erythematosus, as well as new regimens or indications for the use of "standard-of-care" agents such as corticosteroids and cyclophosphamide.

RECENT FINDINGS

Important developments have occurred during the past 2 years as interest in this area has increased, largely because of the participation of pharmaceutical and biotechnical companies in the development and testing of novel agents for systemic lupus erythematosus. Several important large-scale, multicenter, randomized controlled trials have been completed, but none has yet resulted in a new, approved indication for systemic lupus erythematosus. Many issues in the identification of new therapeutic modalities remain. These include the fact that a majority of published reports include either small numbers of patients in controlled trials that lack statistical power to draw conclusions, or are uncontrolled anecdotal series or individual case reports. Among the larger controlled trials, a pervasive issue in the failure to reach statistical significance may be the initial study design. Inclusion of patients with mild and/or stable disease activity does not allow for an effect size sufficient to show differences in treatment arms without recruitment of very large numbers of subjects. Finally, several potentially important trials have been reported only in abstract form to date. Further assessment of the results must await formal publication of these studies.