Longitudinal study on the production of and cellular response to interleukin-2 in patients with systemic lupus erythematosus

Chronic Immune Activation in Systemic Lupus Erythematosus and the Autoimmune PTPN22 Trp620 Risk Allele Drive the Expansion of FOXP3+ Regulatory T Cells and PD-1 Expression

In systemic lupus erythematosus (SLE), perturbed immunoregulation underpins a pathogenic imbalance between regulatory and effector CD4⁺ T-cell activity. However, to date, the characterization of the CD4⁺ regulatory T cell (Treg) compartment in SLE has yielded conflicting results. Here we show that patients have an increased frequency of CD4⁺FOXP3⁺ cells in circulation owing to a specific expansion of thymically-derived FOXP3⁺HELIOS⁺ Tregs with a demethylated FOXP3 Treg-specific demethylated region. We found that the Treg expansion was strongly associated with markers of recent immune activation, including PD-1, plasma concentrations of IL-2 and the type I interferon biomarker soluble SIGLEC-1. Since the expression of the negative T-cell signaling molecule PTPN22 is increased and a marker of poor prognosis in SLE, we tested the influence of its missense risk allele Trp⁶²⁰ (rs2476601C>T) on Treg frequency. Trp⁶²⁰ was reproducibly associated with increased frequencies of thymically-derived Tregs in blood, and increased PD-1 expression on both Tregs and effector T cells (Teffs). Our results support the hypothesis that FOXP3⁺ Tregs are increased in SLE patients as a consequence of a compensatory mechanism in an attempt to regulate pathogenic autoreactive Teff activity. We suggest that restoration of IL-2-mediated homeostatic regulation of FOXP3⁺ Tregs by IL-2 administration could prevent disease flares rather than treating at the height of a disease flare. Moreover, stimulation of PD-1 with specific agonists, perhaps in combination with low-dose IL-2, could be an effective therapeutic strategy in autoimmune disease and in other immune disorders.

The contribution of interleukin-2 to effective wound healing

Ineffective skin wound healing is a significant source of morbidity and mortality. Roughly 6.5 million Americans experience chronically open wounds and the cost of treating these wounds numbers in the billions of dollars annually. In contrast, robust wound healing can lead to the development of either hypertrophic scarring or keloidosis, both of which can cause discomfort and can be cosmetically undesirable. Appropriate wound healing requires the interplay of a variety of factors, including the skin, the local microenvironment, the immune system, and the external environment. When these interactions are perturbed, wounds can be a nidus for infection, which can cause them to remain open an extended period of time, or can scar excessively. Interleukin-2, a cytokine that directs T-cell expansion and phenotypic development, appears to play an important role in wound healing. The best-studied role for Interleukin-2 is in influencing T-cell development. However, other cell types, including fibroblasts, the skin cells responsible for closing wounds, express the Interleukin-2 receptor, and therefore may respond to Interleukin-2. Studies have shown that treatment with Interleukin-2 can improve the strength of healed skin, which implicates Interleukin-2 in the wound healing process. Furthermore, diseases that involve impaired wound healing, such as diabetes and systemic lupus erythematosus, have been linked to deficiencies in Interleukin-2 or defects Interleukin-2-receptor signaling. The focus of this review is to summarize the current understanding of the role of Interleukin-2 in wound healing, to highlight diseases in which Interleukin-2 and its receptor may contribute to impaired wound healing, and to assess Interleukin-2-modulating approaches as potential therapies to improve wound healing.

Quantitative and functional profiles of CD4+ lymphocyte subsets in systemic lupus erythematosus patients with lymphopenia

Lymphopenia is a common clinical manifestation in patients with systemic lupus erythematosus (SLE). However, its physiopathogenic role and the contribution of different T cell subsets in this setting have not been addressed fully. The aim of this study was to characterize T cell subsets quantitatively and functionally and their association with lymphopenia and azathioprine treatment in SLE. We included 84 SLE patients and 84 healthy controls and selected 20 patients for a 6-month longitudinal analysis. Peripheral blood mononuclear cells were isolated, and T cell subsets were analysed by flow cytometry. Functional analyses included autologous and allogeneic co-cultures of T cells. Our data show persistently lower absolute numbers of CD4(+) CD25(high) T cells [regulatory T cells (T(regs) )] (1·9 versus 5·2, P < 0·01) and CD4(+) CD69(+) T cells (3·2 versus 9·3, P = 0·02) and higher activity scores (4·1 versus 1·5, P = 0·01) in SLE patients with lymphopenia compared with those without lymphopenia. Lymphopenia increased the risk for decreased numbers of CD4(+) CD25(high) cells (relative risk 1·80, 95% confidence interval 1·10-2·93; P = 0·003). In addition, azathioprine-associated lymphopenia was characterized by decreased absolute numbers of CD4(+) CD69(+) and CD4(+) interleukin (IL)-17(+) cells compared to disease activity-associated lymphopenia. Functional assays revealed that SLE effector T cells were highly proliferative and resistant to suppression by autologous T(regs) . In summary, lymphopenia was associated with deficient numbers of CD4(+) CD25(high) and CD4(+) CD69(+) cells and resistance of effector T cells to suppression by T(regs) , which could contribute to the altered immune responses characteristic of SLE. Furthermore, azathioprine treatment was associated with decreased numbers of CD4(+) CD69(+) and CD4(+) IL-17(+) cells and diminished T(reg) suppressive activity.

CTL-promoting effects of CD40 stimulation outweigh B cell-stimulatory effects resulting in B cell elimination and disease improvement in a murine model of lupus

CD40/CD40L signaling promotes both B cell and CTL responses in vivo, the latter being beneficial in tumor models. Because CTL may also limit autoreactive B cell expansion in lupus, we asked whether an agonist CD40 mAb would exacerbate lupus due to B cell stimulation or would improve lupus due to CTL promotion. These studies used an induced model of lupus, the parent-into-F1 model in which transfer of DBA/2 splenocytes into B6D2F1 mice induces chronic lupus-like graft-vs-host disease (GVHD). Although agonist CD40 mAb treatment of DBA-->F1 mice initially exacerbated B cell expansion, it also strongly promoted donor CD8 T cell engraftment and cytolytic activity such that by 10 days host B cells were eliminated consistent with an accelerated acute GVHD. CD40 stimulation bypassed the requirement for CD4 T cell help for CD8 CTL possibly by licensing dendritic cells (DC) as shown by the following: 1) greater initial activation of donor CD8 T cells, but not CD4 T cells; 2) earlier activation of host DC; 3) host DC expansion that was CD8 dependent and CD4 independent; and 4) induction of acute GVHD using CD4-depleted purified DBA CD8+ T cells. A single dose of CD40 mAb improved lupus-like renal disease at 12 wk, but may not suffice for longer periods consistent with a need for continuing CD8 CTL surveillance. These results demonstrate that in the setting of lupus-like CD4 T cell-driven B cell hyperactivity, CTL promotion is both feasible and beneficial and the CTL-promoting properties of CD40 stimulation outweigh the B cell-stimulatory properties.

Immunoregulatory defects in patients with systemic lupus erythematosus in clinical remission

Little is known about the immune system of patients with systemic lupus erythematosus (SLE) during periods of silent disease. To address this issue we analysed lymphoid populations andcytokine production of mononuclear cells obtained from SLE patients in remission. We studied 43 patients with inactive disease, 10 with active disease and 30 controls. Remission was defined as at least 1 year during which lack of clinical disease activity permitted withdrawal of all treatment. Remission length ranged from 1 to 30 years. Flow cytometry and ELISA were used to study lymphoid populations (CD4, CD8 and CD19) and cytokine production (IL-2, 4, 10, 12 and 18). Patients with short remission periods (up to 15 years) exhibited an increased percentage of B cells; production of IL-2, IL-10 and IL-12 was decreased; production of IL-18 was increased. Interestingly, patients from groups with long time of inactive disease had corrected most alterations, but had an impaired IL-18 expression. IL-12 production correlated strongly with the length of the remission period (r = 0.7565). The immune system of patients with inactive lupus has partially corrected the disturbances present during disease activity. This is accomplished gradually, sometimes until counter-regulatory alterations are developed. This may allow patients to remain without disease activity.

The expression and significance of intracellular T helper cytokines in systemic lupus erythematosus

To analyze the Th1 and Th2 paradigm of peripheral T helper cells in patients with systemic lupus erythematosus (SLE). The intracellular Th1 and Th2 cytokines were analyzed in fresh blood T cells from 20 SLE patients who had not yet received any treatment. Th1 and Th2 cells were quantitated based on their intracellular cytokine content as assessed by flow cytometry. Cytokine expressions were correlated with clinical features, laboratory findings, and disease activities. There was no difference in the expression of intracellular IFN-y, or IL-4 between SLE patients and healthy controls. However, the IL-2 and IL-10 levels were significantly higher and lower respectively in the lupus patients than in the control group. In addition, patients with arthritis had higher IFN-gamma expression than patients without arthritis. Moreover, patients with serositis or CNS involvement had higher IL-4 expression than in patients without these manifestations. There was no correlation between the SLEDAI scores and the cytokine expression levels. However, patients with serum anti-ds DNA antibodies had higher IL-10 levels than in those without these antibodies. The present study demonstrates that a Th1 pattern of intracellular cytokines predominates in patients with SLE prior to treatment. The pattern of particular intracellular T cell cytokines may suggest specific clinical manifestations and disease progression of SLE.

Efficacy of a pure compound H1-A extracted from Cordyceps sinensis on autoimmune disease of MRL lpr/lpr mice

Cordyceps sinensis (CS) is a traditional Chinese medicine with immunomodulatory effect and is effective in improving the survival of lupus mice. In the present study we isolated a pure compound (H1-A) from CS and investigated its effect on inhibiting autoimmune disease progression in MRL Ipr/Ipr mice. Our results demonstrated that MRL Ipr/Ipr mice treated daily with H1-A (40 microg/kg/d orally) for 8 weeks had a progressive reduction in anti-ds-DNA production (optical density value decreased from 0.172 +/- 0.009 to 0.112 +/- 0.015) when compared with the control group (optical density value increased from 0.141 +/- 0.036 to 0.198 +/- 0.047). In clinical presentation, the treated group had a reduction in lymphadenopathy, a delayed progression of proteinuria, and an improvement in kidney function. Histologic analysis of kidney tissue indicated that H 1-A could inhibit the mesangial proliferation that was evident in lupus nephritis. However, there was no significant change in immune complex deposition. The studies reveal that the pure compound (H1-A) may be potentially useful for treating systemic lupus erythematosus in human patients, and they provide some questions for further investigation of the pathogenesis of systemic lupus erythematosus and lupus nephritis.

Increased interleukin-4 production by NK T cells in systemic lupus erythematosus

It has been reported that production of interleukin (IL)-4, a T helper (Th)-2-type cytokine, might play an important role in the pathogenesis of systemic lupus erythematosus (SLE). On the other hand, it is known that NK1.1(+) cells which belong to CD4, CD8 double-negative, or CD4(+) cells are associated with initial IL-4 production and Th2 differentiation in mice although human equivalent cells are unknown. In order to study the profile of IL-4-producing cells in SLE, cytoplasmic IL-4 and various surface antigens on peripheral mononuclear cells were analyzed. Peripheral mononuclear cells were stimulated for 5 h by phorbol ester and ionomycin in the presence of monensin, fixed, and permeabilized with paraformaldehyde and saponin solution. Then cytoplasmic IL-4 and various surface antigens were analyzed by flow cytometry. IL-4-producing cells in SLE were phenotypically the same as those which produce IL-4 normally and frequently bore activated T-cell (CD7, CD25, CD28, CD29) and NK-cell markers (CD56, CD57). Double-negative T cells and CD57(+) T cells were increased in number and were more frequently positive for cytoplasmic IL-4 in SLE compared with normal controls and various infectious diseases. It was suggested that T cells with NK cell markers, CD57(+) T cells, which are known to extrathymically differentiate, might be involved in the pathogenesis of SLE as a counterpart of mouse NK1.1(+) cells.

Exogenous IL-10 and IL-4 down-regulate IL-6 production by SLE-derived PBMC

The elevated expression of IL-6 and IL-10 may have an important role in SLE pathogenesis. IL-6 production by normal monocytes can be inhibited by IL-10, and it has been suggested that SLE monocytes are refractory to this negative signal. To examine this possibility, the effects of regulatory factors on IL-6 expression by SLE PBMC (N = 51) were compared to effects on control PBMC (N = 21). We found that (1) exogenous rIL-10 and rIL-4 mediated reduction of constitutive and lectin-induced IL-6 in monocytes of SLE patients as effectively as that of controls; (2) IL-6 mRNA decay was significantly delayed in SLE with active disease (P < 0.001); (3) adding rIL-10 or neutralizing endogenous IL-1 beta and TNF-alpha down-regulated IL-6 mainly by destabilizing IL-6 transcripts, whereas exogenous IL-4 and TGF beta 1 down-regulated IL-6 transcriptionally; (4) time kinetics and levels of IL-10 were lower than those of IL-6 and IL-1 beta. Thus, contrary to a previous report, IL-6 production by SLE PBMC responds normally to regulatory signals, and the IL-6 overexpression in SLE may be due, at least in part, to the kinetics and availability of regulatory cytokines.

Decreased Th1-like and increased Th2-like cells in systemic lupus erythematosus

The proportion of the lymphocytes which produce the cytokines corresponding to murine T helper- (Th1) or Th2 cells was studied using flow cytometry in systemic lupus erythematosus (SLE). When the peripheral mononuclear cells were stimulated with phorbol myristate acetate and ionomycin in the presence of monensin, which blocks the secretion of cytokines, the positive rates for the cytoplasmic IL-2 and IFN-gamma were lower and those for the cytoplasmic IL-4 and IL-10 were higher in SLE than in normal subjects. When the cells were cultured with monensin alone, the positive rates for these 4 cytokines were slightly increased in SLE. These data suggest that the mononuclear cells are already activated in vivo and a deviation of the proportion of the Th cells to the Th2-like ones might be associated with the polyclonal B cell activation seen in SLE.

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

Systemic lupus erythematosus (SLE) is a highly heterogeneous disorder in which multiple immunologic abnormalities have been described. In this review, we thoroughly analyse the impaired T cell production of, and response to, interleukin-2 (IL-2) characteristic of patients with SLE. Since it was first reported, several articles have provided us with enlightening, but somewhat confusing, data that reveal the complexity of the subject. The IL-2 production by T cells is part of a complex network in which a discrete alteration is capable of disrupting the whole system. On the other hand, regulatory mechanisms exist that, in an attempt to compensate the primary alteration, provoke secondary defects. Evidence indicates that this defect is not intrinsic, but rather, results from multiple microenvironmental influences that act on the T cell and modify its activation state and its cytokine production. Abnormalities in co-stimulatory mechanisms and in cytokines that may be related to the IL-2 production deficiency, have been described in patients with SLE. We also consider the information derived from murine SLE models, IL-2 knockout models and reports concerning the immune dysregulation present in patients with SLE.