Interleukin-2 and systemic lupus erythematosus--fifteen years later

Restoring regulation - IL-2 therapy in systemic lupus erythematosus

INTRODUCTION

The pathogenesis of systemic lupus erythematosus (SLE) involves an acquired deficiency of the cytokine IL-2, an essential growth and survival factor for regulatory T cells (Treg), which play an important role in the control of autoimmunity in SLE. In contrast to currently available therapies that broadly suppress the immune system, low-dose IL-2 therapy in SLE aims to compensate the pre-existing IL-2 deficiency and thus to restore a physiological state, where Treg can regain their ability to efficiently counteract autoimmunity. Areas covered: Here we summarize key findings that led to the development of this novel therapeutic concept and will highlight the key rationales for the clinical translation of low-dose IL-2 therapy in SLE. Expert commentary: The concept of low-dose IL-2 therapy in SLE has evolved from pathophysiological findings and thus can be considered a selective biological treatment strategy in SLE. Preliminary results from phase I/II studies are promising by proving selective Treg expansion and by providing first evidence for the clinical efficacy of low-dose IL-2 therapy in SLE.

CD4⁺CD25⁺ regulatory T cells from MRL/lpr mice were functionally more active in vitro but did not prevent spontaneous as well as adriamycin-induced nephropathy in vivo

OBJECTIVE

The frequency and function of Tregs are important in the pathogenesis of SLE. Nonetheless, the function of Tregs is still controversial in SLE patients and lupus mouse models. In the present study, we investigated the suppressive function of Tregs from MRL/lpr mice in vitro and in vivo by using an alternative quantitative assay.

METHODS

We assessed the suppressive function of CD4(+)CD25(+) Tregs, the proliferative activity of CD4(+)CD25(-) effector T cells (Teffs) and the feeder activity of CD11c(+) dendritic cells (DCs), isolated from the spleens of MRL/lpr mice and wild-type (WT) MRL/+ mice, by carboxyfluorescein diacetate succinimidyl ester dilution assay stimulated with two distinct types of signals, weak and strong. In order to assess the protective function of Tregs from an immune-mediated disease in vivo, we induced renal damage by injecting adriamycin (ADN) into the mice.

RESULTS

The in vitro assay showed enhanced suppressive activity of Tregs and feeder activity of DCs, but far less proliferative activity of Teffs from MRL/lpr mice, compared with those from the WT mice. The in vivo study showed more severe ADN-induced nephropathy in MRL/lpr mice than in the WT mice, while mild interstitial nephritis had already begun spontaneously by 16 weeks in MRL/lpr mice.

CONCLUSION

It was suggested that Tregs from MRL/lpr mice were functionally competent and intrinsically more active in vitro, but they were not capable of preventing the ADN-induced as well as the spontaneously developing nephropathy in vivo.

Homeostatic imbalance of regulatory and effector T cells due to IL-2 deprivation amplifies murine lupus

The origins and consequences of a regulatory T cell (Treg) disorder in systemic lupus erythematosus (SLE) are poorly understood. In the (NZBxNZW) F(1) mouse model of lupus, we found that CD4(+)Foxp3(+) Treg failed to maintain a competitive pool size in the peripheral lymphoid organs resulting in a progressive homeostatic imbalance of CD4(+)Foxp3(+) Treg and CD4(+)Foxp3(-) conventional T cells (Tcon). In addition, Treg acquired phenotypic changes that are reminiscent of IL-2 deficiency concomitantly to a progressive decline in IL-2-producing Tcon and an increase in activated, IFN-gamma-producing effector Tcon. Nonetheless, Treg from lupus-prone mice were functionally intact and capable to influence the course of disease. Systemic reduction of IL-2 levels early in disease promoted Tcon hyperactivity, induced the imbalance of Treg and effector Tcon, and strongly accelerated disease progression. In contrast, administration of IL-2 partially restored the balance of Treg and effector Tcon by promoting the homeostatic proliferation of endogenous Treg and impeded the progression of established disease. Thus, an acquired and self-amplifying disruption of the Treg-IL-2 axis contributed essentially to Tcon hyperactivity and the development of murine lupus. The reversibility of this homeostatic Treg disorder provides promising approaches for the treatment of SLE.

Telomere length analysis in monocytes and lymphocytes from patients with systemic lupus erythematosus using multi-color flow-FISH

In order to analyse telomere length in subsets of human peripheral blood lymphocytes and monocytes, we modified a recently developed multicolor flow- fluorescent in situ hybridization (FISH) methodology that combines flow-FISH and antibody staining for cell surface antigens. We analysed telomere length of peripheral blood mononuclear cells in a group of 22 patients with systemic lupus erythematosus (SLE) and 20 age-matched healthy donors. We found that neither CD4+, CD8+, CD19+ cells nor CD14+ monocytes have significantly shorter telomeres compared with their healthy counterparts. On the basis of these findings, we then used monocyte telomere length as internal reference in order to control for intra-individual variability in telomere length. By using this approach, we could demonstrate significant telomere shortening in all three lymphocyte subsets (in all cases P < 0.05) compared with monocytes. However, these differences did not vary significantly between SLE patients and controls. In summary, telomere lengths in subpopulations of hematopoietic cells can be monitored in patients with SLE using multicolor flow-FISH. While confirming data by other groups on telomere length in lymphocyte subpopulations, our data argue against an increased proliferation rate of peripheral blood monocytes reflected by accelerated telomere shortening in patients with SLE.

Ex vivo interleukin 1 receptor antagonist production on lipopolysaccharide stimulation is associated with rheumatoid arthritis and with joint damage

OBJECTIVES

(1) To assess innate ex vivo production of interleukin 1beta (IL1beta) and interleukin 1 receptor antagonist (IL1Ra) in patients with recent-onset rheumatoid arthritis (RA) as compared with healthy controls; (2) to assess the association of ex vivo IL1beta and IL1Ra production with progression of joint damage in RA; (3) to determine whether differences in ex vivo IL1beta production are explained by distribution of the IL1beta single nucleotide polymorphism C-511T.

METHODS

Levels of IL1beta and IL1Ra (measured by ELISA after whole-blood stimulation with lipopolysaccharide) and distribution of IL1beta C-511T were compared in 76 patients with recent-onset RA who had received no disease-modifying antirheumatic drugs (DMARDs), and 63 healthy controls. ORs for RA based on ex vivo IL1beta and IL1Ra production were calculated. Association of ex vivo IL1beta and IL1Ra production with progression of joint damage (Sharp-van der Heijde score over 2 years) was determined by linear regression with correction for baseline characteristics.

RESULTS

Patients with recent-onset RA showed lower ex vivo IL1beta and higher ex vivo IL1Ra production than healthy controls (p<0.001), with ORs for RA of 2.4 (95% CI 1.2 to 4.9) for low IL1beta-producers and 7.6 (95% CI 3.2 to 18.0) for high IL1Ra-producers. High ex vivo IL1Ra production was associated with progression of joint damage (p = 0.01). The IL1beta C-511T genotype distribution was not significantly different between patients and controls.

CONCLUSIONS

Patients with recent-onset RA had decreased ex vivo IL1beta production and increased ex vivo IL1Ra production compared with controls. Ex vivo IL1Ra production is an independent predictor of progression of joint damage in recent-onset RA.

Control of interleukin-2 gene transcription: a paradigm for inducible, tissue-specific gene expression

Interleukin-2 (IL-2) is a key cytokine that controls immune cell function, in particular the adaptive arm of the immune system, through its ability to control the clonal expansion and homeostasis of peripheral T cells. IL-2 is produced almost exclusively by T cells in response to antigenic stimulation and thus provides an excellent example of a cell-specific inducible gene. The mechanisms that control IL-2 gene transcription have been studied in detail for the past 20 years and our current understanding of the nature of the inducible and tissue-specific controls will be discussed.

A mutation of the glucocorticoid receptor gene in patients with systemic lupus erythematosus

We screened for mutations of the glucocorticoid receptor (GR) gene in patients with systemic lupus erythematosus (SLE), a typical autoimmune disease. Polymerase chain reaction-single-strand conformation polymorphism analysis (PCR-SSCP) revealed a single mutation in exon 9 of the GR gene in 11/132 (8.3%) among 66 patients with SLE. No mutations were detected in 52 healthy individuals (0/104, 0.0%), but the same mutation was detected in other autoimmne diseases (4/108, 3.7%). DNA sequencing showed a T to C substitution at codon 766 (position 2430) of the GR gene, which does not alter the amino acid sequence of the GR. Further analysis using a LightCycler generated different melting curves indicates that the pattern with this mutation is different from that of wild type. The identified mutation of the GR gene may represent a polymorphism associated with SLE.

High-producer interleukin-2 genotype increases risk for acute graft-versus-host disease after unrelated donor bone marrow transplantation

BACKGROUND

Cytokine polymorphisms may modulate immunologic reactivity, including graft-versus-host disease (GVHD). A single nucleotide polymorphism resulting in a thymine-to-guanine transition in the interleukin (IL)-2 gene promoter region occurs at position -330. In vitro studies have shown that the G allele is associated with early and sustained enhancement of IL-2 production, a so-called high-producer genotype. Because IL-2 is a proinflammatory cytokine, we hypothesized that recipients with high-producer genotypes would have increased frequency of GVHD after allogeneic bone marrow transplantation (BMT).

METHODS

We studied 95 consecutive donor and recipient pairs who received an unrelated donor BMT at the University of Minnesota. The median age at time of BMT was 14.1 years (range 0.9-54.8 years). Stem cells were human leukocyte antigen-A, B, and DRB1 matched in 70 cases (74%) and single-antigen mismatched in 25 cases (26%). GVHD prophylaxis consisted of cyclosporine-containing regimens (53%), T-cell depletion by elutriation (42%), and others (2%).

RESULTS

The probability of grade II-IV acute GVHD at day 100 was 36% (95% confidence interval 26%-46%) and was significantly affected by the presence of recipient IL-2 G allele. The probability of acute GVHD was 49% in 49 patients (52%) with at least one G allele compared with 24% in 42 patients (44%) with no G allele (P<0.01). In the Cox regression analysis, the presence of at least one IL-2 G allele was associated with a twofold increased risk of acute GVHD.

CONCLUSIONS

If confirmed by others, our results indicate that more intensive GVHD prophylaxis is needed for patients with at least one IL-2 G allele, possibly directed toward blunting early host cell production of IL-2.

Direct transfer of p65 into T lymphocytes from systemic lupus erythematosus patients leads to increased levels of interleukin-2 promoter activity

The recent identification of a number of molecular defects in T cells from patients with systemic lupus erythematosus (SLE) has raised expectations for gene replacement therapy as an option in the treatment of these diseases. In this report, we have adapted an electroporation-based technique to transfer successfully DNA to peripheral blood T cells from normal individuals and patients with systemic lupus erythematosus and rheumatoid arthritis. Transfection efficiency, judged by the percentage of live cells expressing green fluorescence after transfection with a pGFP (green fluorescence protein), reached 32 +/- 3% in normal, 13 +/- 3% in SLE, and 17 +/- 13% in RA T cells. The transfection efficiency was slightly higher in CD8+ than in CD4+ cells, and the cells maintained acceptable (75%) viability up to the fourth post-transfection day. SLE T cells have been shown to display low levels of the p65 subunit of the NF-kappaB transcription factor and decreased production of IL-2. Since NF-kappaB contributes to the transcriptional regulation of the IL-2 promoter, the effect of the forced replenishment of p65 on IL-2 transcription was tested. The low level of interleukin-2 promoter activity in SLE T cells increased to normal levels following transfection with cDNA encoding the NF-kappaB p65 subunit. Taken together, these results demonstrate the feasibility of transfection of T cells from SLE patients by electroporation and the reversal of decreased interleukin-2 promoter activity in SLE T cells, and are an early step toward gene therapy as a method of treatment for these individuals.

Cytokines and autoimmunity

Cytokines have crucial functions in the development, differentiation and regulation of immune cells. As a result, dysregulation of cytokine production or action is thought to have a central role in the development of autoimmunity and autoimmune disease. Some cytokines, such as interleukin-2, tumour-necrosis factor and interferons--ostensibly, the 'bad guys' in terms of disease pathogenesis--are well known for the promotion of immune and inflammatory responses. However, these cytokines also have crucial immunosuppressive functions and so, paradoxically, can also be 'good guys'. The balance between the pro-inflammatory and immunosuppressive functions of these well-known cytokines and the implications for the pathogenesis of autoimmune disease is the focus of this review.

Association of cytokine polymorphic inheritance and in vitro cytokine production in anti-CD3/CD28-stimulated peripheral blood lymphocytes

BACKGROUND

Genetic variations in cytokine genes are thought to regulate cytokine protein production. However, studies using T cell mitogens have not always demonstrated a significant relationship between cytokine polymorphisms and in vitro protein production. Furthermore, the functional consequence of a polymorphism at position -330 in the IL-2 gene has not been described. We associated in vitro protein production with cytokine gene polymorphic genotypes after costimulation of cultured peripheral blood lymphocytes.

METHODS

PBL were isolated from forty healthy volunteers. Cytokine protein production was assessed by enzyme-linked immunosorbent assay. Polymorphisms in interleukin- (IL) 2, IL-6, IL-10, tumor necrosis factor (TNF-alpha), tumor growth factor (TGF-beta), and interferon (IFN-gamma) were determined by polymerase chain reaction (PCR).

RESULTS

Statistical difference between protein production and cytokine polymorphic variants in the IL-10, IFN-gamma, and TNF-alpha genes was not evident after 48-hour stimulation with concanavalin-A. In contrast, after anti-CD3/CD28 stimulation significant differences (P<0.05) were found among high and low producers for IL-2, IL-6, and among high, intermediate, and low producers for IFN-gamma, and IL-10. Augmented levels of IL-2 in individuals that were homozygous for the polymorphic IL-2 allele were due to an early and sustained enhancement of IL-2 production. No association was found among TNF-alpha and TGF-beta genotypes and protein production.

CONCLUSION

Polymorphisms in IL-2, IL-6, IL-10, and IFN-gamma genes are associated with their protein production after anti-CD3/CD28 stimulation. The profound effect of the IL-2 gene polymorphism in homozygous individuals may serve as a marker for those that could mount the most vigorous allo- or autoimmune responses, or perhaps become tolerant more easily.

Serum interleukin-15 is elevated in systemic lupus erythematosus

OBJECTIVE

To investigate if interleukin-15 (IL-15) (rather than IL-2) is increased in systemic lupus erythematosus (SLE) and might be responsible for immunological abnormalities of SLE such as the increased lymphocytic expression of Bcl-2 and CD25.

METHODS

Serum IL-15, IL-2 and tumour necrosis factor (TNF) levels of 65 SLE patients, 20 healthy persons and 10 rheumatoid arthritis (RA) patients were measured by enzyme-linked immunosorbent assay (ELISA). For 25 SLE patients, the percentage of CD25 + lymphocytes and the lymphocytic Bcl-2 levels were simultaneously determined by fluorocytometry. Peripheral blood mononuclear cells (PBMC) of 15 SLE patients were incubated with or without recombinant IL-15 and the influence on Bcl-2 and CD25 was determined.

RESULTS

IL-15 was found to be elevated in 25 SLE sera (38%), but in none of the 20 healthy sera (P = 0.0005) and none of the 10 RA sera. Both lymphocyte CD25 and Bcl-2 expression significantly correlated with serum IL-15 and were increased by recombinant IL-15.

CONCLUSION

Serum IL-15 may in part be responsible for the immunological abnormalities seen in active SLE.

Cytokine regulation of apoptosis and Bcl-2 expression in lymphocytes of patients with systemic lupus erythematosus

Both faulty regulation of apoptosis and the inappropriate expression of several interleukins have been considered important defects of lymphocytes in the human autoimmune disease systemic lupus erythematosus (SLE). We therefore tested the in vitro effect of recombinant interleukin (IL-)-2, 4, 7, and 15 on peripheral blood mononuclear cells from patients with SLE and from healthy volunteers. Intracellular Bcl-2 and Bax expression was measured by fluorocytometry and the rate of apoptosis was determined by the TUNEL technique and propidium iodide staining. IL-2, IL-4, IL-7 and IL-15 led to a significant increase in Bcl-2 and a reduction in cell death rates, which was even more pronounced in SLE. Bax levels remained unchanged. Interestingly, the high ex vivo Bcl-2 content of lymphocytes from some SLE patients was maintained after growth factor withdrawal. Anti-apoptotic cytokine signaling may significantly influence the deregulation of cell death in SLE lymphocytes.