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Volume 25 No. 1 June 2011 Peer reviewed rEviEW
PATHOGENESIS AND FUTURE TREATMENTS OF SYSTEMIC LUPUS
ERYTHEMATOSUS: THE ROLE OF CYTOKINES AND ANTI-CYTOKINES?
W. J. Maule
University of Johannesburg, Department of Biomedical Technology, Faculty of Health Sciences, South Africa.
email: [email protected] tel: +27 (0)11 559 6265 fax: +27 (0)11 559 6558
cytokine production and cytokine levels in patients with slE
Systemic lupus erythematosus (SLE) is a chronic multisystem Several cytokines are in involved in the pathogenesis of SLE [11] autoimmune connective tissue disorder, which has variable and more than 30 years ago [12] immune interferon (IFN-γ) was clinical manifestations that range from mild to life-threatening found in the serum of patients with SLE and showed a good [1]. These can be characterised by multiple organ damage, very correlation between (IFN-γ) titres and disease activity.
high titres of autoantibodies and immune complex deposition. T-helper cells 1 (Th1) cytokines such as IFN-γ, IL-12, and Interestingly the former of these characteristics may precede T-helper cells 2 (Th2) cytokines IL-4, IL-6 and IL-10 are each the clinical manifestations of SLE by many years [1]. It is well considered to play a role in the course of human SLE [13, 14]. recognised that the probable influence of oestrogen hormonal Other proinflammatory cytokines such as IL-1, IL-17, IL-23 and effect in women during childbearing years increases their chances tumour necrosis factor alpha (TNFα) [15] are also involved along of developing SLE by 10-15 times [2-5]. The immunopathogenic with these Th1 and Th2 cytokines.
hallmark of SLE is the polyclonal B cell activation, which leads to hyperglobulinanaemia, autoantibody production and immune complexes. All of these factors contribute to the conventional belief that SLE is a disease primarily of these autoantibodies and immune complex deposition, the latter contributing to inflammation by virtue of complement activation and the engagement of complement and fragment crystallisable (Fc) – receptors [6, 7] ultimately inflicting injury to a variety of organ systems (Figure 1). Mediation of these inflammatory responses is characterised by the influx of various cell populations and also to a large extent by the generation of proinflammatory cytokines. The clinical manifestations in inflammatory diseases such as SLE and rheumatoid arthritis (RA) are thought to be influenced by the balance between proinflammatory and anti-inflammatory cytokines [9].
Cytokines are soluble factors and are mainly produced by helper T (Th) cells. They also play a crucial role in the differentiation, maturation and activation of various immune cell types [8]. In order to monitor disease activity and predict disease severity certain cytokines may act as biomarkers [9]. Recent work for example, using microarray techniques and genetic analysis has strengthened the association between cytokine dysregulation and SLE [10]. These breakthroughs show some promise in understanding the immunoregulatory networks of autoimmune diseases, which are influenced by multiple factors, particularly in regard to these cytokines and their interactions.
Through systematic review of published literature,
only those cytokines that have significant
involvement in the pathogenesis of SLE in the
‘human model' and those that represent a
relatively easy target for therapeutic intervention Figure 1: Simplified diagram of the Immunopathogenesis of SLE.
(i.e. the anti-cytokines) will be reviewed.
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Volume 25 No. 1 June2011 Figure 2: IL-6-producing cells and biological activities of IL-6. IL-6 is produced by lymphoid and nonlymphoid cells, such as
T cells, B cells, monocytes, fibroblasts, keratinocytes, endothelial cells, mesangial cells, and several kinds of tumor cell (top
of figure). IL-6 also has a wide range of biological activities on various target cells (bottom of figure).
(reproduced with permission [36])
1. interleukin 6 (il-6)
to stimulate the monocyte/macrophage fraction of PBMCs taken from SLE patients to produce IL-6 [26]. Another interesting IL-6 is a proinflammatory cytokine which is synthesised observation was that lymphoblastoid cells that were isolated principally by monocytes, fibroblasts and endothelial cells from SLE patients exhibited high levels of IL-6 and blocking IL- (Figure 2). IL-6 secretion can also be found in both T and 6, which resulted in the inhibition of anti-dsDNA production B lymphocytes [15] and its production is stimulated by IL- in vitro [27] . However, using a widely applied method to study α, but subdued by IL-4, IL-10 and IL-13. In combination with type 1 interferons, one of the most important the activation of the innate immune system i.e. the in vitro effects of IL-6 is to activate B lymphocytes, drive plasma-cell stimulation of whole blood using lipopolysaccharide (LPS), IL-6 differentiation and to augment the immunoglobulin secretion [16, production was significantly lower in SLE patients as compared 17]. Additionally, IL-6 acts on multipotential progenitor cells, is a to normal individuals [28]. neutrophil activator and stimulates megakaryocytes to produce Unlike normal individuals, B lymphocytes from SLE patients platelets. It also induces terminal macrophage and osteoclast were found to spontaneously generate large amounts of differentiation as well as pyrexia and the production of acute immunoglobulins (Ig). There was however, a significant reduction phase proteins [36].
in this Ig production when IL-6 was blocked and this production In total contrast to these proinflammatory effects, IL-6 is also was only restored after exogenous IL-6 administration [23]. In involved in a number of unique anti-inflammatory reactions. For addition these B lymphocytes also secrete anti-double-stranded example, IL-1 and TNF-α stimulate the synthesis of each other DNA (anti-ds DNA), with different B lymphocyte populations as well as IL-6, however, the latter is involved in terminating contributing to this in a number of different ways. For example, this reaction as well as being involved in the upregulatory it was shown that the majority of these autoantibodies were inflammatory cascade [17].
produced ex vivo by low density B lymphocytes [29], whereas The association of IL-6 in the pathogenesis of SLE in humans is high density B cells had little effect. It was also shown that still controversial [18] although support for this association has in response to IL-6, low density B lymphocytes from patients been published using several murine models [19-21].
with active SLE were capable of directly differentiating into Ig secreting cells [30]. CD5 expression is also down-regulated 1.1. role of il-6 in human slE
by IL-6 via DNA methylation, which promotes activation and Human SLE patients have been shown to have increased IL-6 [22- subsequent expansion of auto-reactive B cells seen in SLE 24] levels that are allied to disease activity [23] or anti-DNA levels patients [30]. The IL-6 abnormalities seen in SLE may well be [22], in some but not all studies [24].
due, in part to, genetic differences. For example, Linker-Israeli In one study [25], SLE patients had a significantly higher frequency et al [31] demonstrated that alleles of the adenosine/tyrosine (AT) of IL-6 secreting peripheral blood mononuclear cells (PBMCs) rich minisatellite situated in the 3' region flanking the IL-6 gene, compared to those of healthy controls. This may well be due to was associated with SLE patients of either Caucasian or African- environmental factors as exposure to UV light has been shown American origin, but not in the control group.
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Volume 25 No. 1 June 2011 It is well proven that the classical marker auto-antibodies There was a notable reduction in inflammatory markers, auto- seen in SLE are anti-ds DNA antibodies and although the titre of antibody levels and in disease activity (SELENA-SLEDAI from those antibodies in the serum of SLE patients can be a reflection 9.5 at baseline to 5.5 at 20 weeks) with a median decrease of of disease activity in lupus nephritis, for example, their exact 38% in the 4 mg/kg dosage group and 56% in the 8 mg/kg role remains unclear. It has been shown however, that anti- dosage group. Unfortunately almost all the patients developed dsDNA can have a direct effect on cytokine expression in a a significant dose-related neutropenia with concomitant high variety of cells. They can also upregulate the expression of the rates of infections [50]. proinflammatory cytokines IL-1 and IL-6 in endothelial cells [32- Although neutropenia may limit the maximum dosage of 34] and they can stimulate the expression and release of IL-1, tocilizumab in patients with SLE, the observed clinical and IL-6, IL-8, IL-10 and TNF [35] (from human resting mononuclear serological responses are promising and warrant further studies to establish the optimal dosing regimen and efficacy.
1.2. il-6 and lupus nephritis
2. interleukin 10 (il-10)
IL-6 has been shown in several studies to have proliferative The cytokine IL-10 is mainly produced by lymphocytes effects on mesangial cells thereby modulating injury in and monocytes. It also impedes the activation of antigen immunologically generated nephritis. Two studies demonstrated presenting cells (APCs) and down-regulates the expression of that mesangial proliferation in mesangial proliferative co-stimulatory molecules such as major histocompatibility glomerulonephritis correlated well with the urinary IL-6 levels complex class II (MHC II) and B7 expression [51]. IL-10 also [37, 38]. Further studies demonstrated high urinary excretion of inhibits T cell function by diminishing the expression of other IL-6 in patients with active lupus nephritis. The levels of IL-6 proinflammatory cytokines such as TNFα, IL-1, IL-6, IL-8 were significantly elevated in patients with proliferative lupus and IL-12 [52, 53]. In addition to these inhibitory functions IL- nephritis (World Health Organisation (WHO) Class III and IV) 10 boosts B cell mediated proliferation, thereby increasing with concomitant high titres of anti-dsDNA antibodies [39, 40]. survival, proliferation, differentiation and immunoglobulin class IL-6 levels were also found to be much higher in patients with switching, resulting in increased antibody secretion, which active nephritis as compared to those patients with dormant promotes the inflammation seen in SLE [54].
renal disease [24, 40]. Additionally it was found that there was In particular, the production of IL-10 and TNFα, two mutually enhanced in situ expression of IL-6 in lupus nephritis, mainly associated cytokines, play a complex and opposite role in these along the renal glomeruli and tubles [41-43].
systemic inflammatory responses that has been found to be Interestingly IL-6 has also been shown to have a positive deregulated in SLE patients (Figure 3).
association with the Neuropsychiatric syndromes of systemic All these findings, plus the addition of environmental influences lupus erythematosus (NPSLE). For example elevated levels of are suggestive of a combination between genetic and disease- IL-6 have been reported in the cerebrospinal fluid (CSF) of induced events. IL-10 and TNFα for example, have been linked patients with NPSLE, without subsequent damage to the blood- to SLE and genetic polymorphorisms at the promoter regions of brain barrier [44-46].
both these genes [55] is associated with their over production, To summarise, IL-6 has an important role in mediating local particularly that of IL-10 [56]. However, previous studies of a inflammation and insults of various tissues.
much larger magnitude which included patient family members with increased IL-10 production [57], failed to confirm this 1.3. therapeutic implications of il-6 in slE
association [58].
As previously stated in a number of studies, IL-6 was found to Increased IL-10 production might also explain B cell be elevated in both human and murine lupus [21-24].
hyperactivity and autoantibody production, two of the main IL-6 released from PBMC for example, directly correlated indicators of the immune dysregulation seen in SLE.
with disease activity and the treatment response seen in lupus In line with this; the association between IL-10, disease activity, nephritis patients [47].
immune complexes isolated from the serum of SLE patients Other studies have confirmed that there was an increased as well as monoclonal anti-dsDNA antibodies, induced IL- expression of the IL-6 agonistic receptor gp130 on peripheral 10 production in healthy monocytes [35, 59]. IL-10 might also lymphocytes in SLE patients, and that the levels correlated with regulate dendritic cells (DCs) and T cell function, by promoting overall disease activity [47, 48].
Th2 deviation of the overall immune response (Figure 3) [60].
Taking this into account it has been suggested that gp130 could 2.1. therapeutic implications of il-10 in slE
be a useful biomarker to monitor both the activity of disease and subsequent treatment responses in those patients [48].
Although one of the major factors is still the absence of a Using murine models where the success of IL-6 antagonism is therapeutic agent which is suitable for long-term administration well proven, a phase 1 dose finding study was set up to evaluate in human patients with SLE IL-10 was the first cytokine to be the use of a monoclonal antibody tocilizumab (Anti-IL-6 R blocked [64], which has led to use of anti-IL-10 antibody in the Ab) in human SLE patients [49]. A total of sixteen patients with treatment of this disease [61].
moderately active disease [as defined by the Safety of Estrogens An over-production of IL-10 has been demonstrated in murine in Lupus Erythematosus National Assessment (SELENA) and models of SLE [62]. Using continuous early-onset therapy with an Systemic Lupus Erythematosus Disease Activity Index (SLEDAI), anti-IL-10 antibody however, delayed autoimmunity in NZB/W (i.e. a SELENA-SLEDAI score of between 3 and 10 or active mice and improved their overall survival rate from 10 to 80% glomerulonephritis] were given tocilizumab in one of three [63]. In a pilot study using an anti-IL-10 murine monoclonal doses (2 mg/kg in 4 patients, 4 mg/kg in 6 patients, and 8 mg/ antibody (MoAb), which neutralizes human IL-10, Llorente et kg in 6 patients) twice weekly for 12 weeks. Patients were then al. [64] evaluated the clinical efficacy and safety of this antibody monitored for an additional 8 weeks [50].
in a total of six patients with steroid dependent SLE.
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Volume 25 No. 1 June2011 Figure 3: Interactions of IL-10 and TNFα and their role in the development of SLE. This figure represents a simplified model
of the complex relationship between IL-10 and TNFα in lupus disease. Both cytokines are produced by multiple cells types
of the innate and adaptative immune system, in particular DCs, monocytes/macrophages, (Mø) and specific effector T cells.
Th1 cells produce the proinflammatory cytokine TNFα which activates DCs and other antigen presenting cells (APCs), and
induces the production of IL-10. In addition, TNFα promotes inflammation and apoptosis, generating neoantigens that could
result in autoantibody production. On the other hand, IL-10, a Th2 cytokine, antagonise Th1 differentiation and inhibits
APCs and T cells. Conversely, IL-10 is a potent stimulator of B cell proliferation, differentiation and antibody production.
Thus, B cell activation in presence of neo-antigens may lead to autoantibody secretion and immune complexes formation,
thus resulting in tissue damage affecting diverse organs. STAT; signal transducer and activator of transcription.
(reproduced with permission [55])
The treatment consisted of administering 20mg/day of MoAb of transforming growth factor (TGF-β) and other important intravenously for a total of 21 consecutive days. The patients inflammatory cytokines including IL-6, IL-21 and IL-23 [68-70]. were then followed up monthly for a total period of 6 months. The latter also enhances IL-17 production by memory T cells [71].
The therapy was well tolerated in all six patients and although These observations strongly suggest that the presence of an all had significant improvement of their cutaneous lesions inflammatory signal of some sort is required to transform these and/or joint symptoms during MoAb administration, they also naïve CD4 T cells to become pro-inflammatory. The cytokine developed antibodies against it. IL-21 for example, was found to influence Th-17 differentiation. This study not only suggests that the use of MoAb may be of Unlike IL-6 it is produced by Th17 cells and the T-follicular benefit in the management of refractory SLE, but that a much helper cells, but not by APCs. Mangan et al [70] claimed that larger, randomized and blinded study using a humanized anti- one of its functions was that of an auto-amplifier of the Th17 IL-10 MoAb is required. Such an agent might soon be available response. IL-17 also upregulates the expression of intercellular adhesion molecule-1 (ICAM-1) through the facilitation of T cell activation and infiltration into tissues [72]. Th17 cells can also 3. interleukin 17 (il-17)
assist as an independent T helper effector cell subset, which IL-17 is an ancient cytokine, and is a type 1 transmembrane promote an inflammatory response through cytokine secretion protein, produced by activated T cells and is intimately related to (i.e. IL-17A, IL-17F, IL-21 and IL-22) (Figure 4) [73]. In regard epithelia, especially those of the intestinal mucosa [65, 66]. IL-17 is to the pathogenesis of SLE, this collection of cytokines can a potent pro-inflammatory cytokine that also plays an important stimulate B lymphocytes, to initiate the local inflammation and role in the immune response against fungi and bacteria [67]. tissue injury often seen in this disease [73].
As stated, IL-17 is produced by activated T lymphocytes, with Recent studies support and confirm the role of IL-17 in SLE the ‘Th17' cells being the most energetic producer. Th17 cells pathogenesis [74, 75].
originate when naïve CD4 T cells are primed in the presence 8 www.smltsa.org.za ISSN 1011 5528

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Volume 25 No. 1 June 2011 Figure 4: Proposed model for the role of T-helper type 17 (Th17) cells and interleukin (IL)-17
in the pathogenesis of systemic lupus erythematosus (SLE) (reproduced with permission [72]).
CD4+ cells differentiate into Th1, Th2 and Th17 effector cells as well as double-negative (DN) T
cell subsets. The cytokine milieu characteristic of SLE patients (lack IL-2; high levels of IL-6 and
IL-21) could promote Th17 expansion. Th17 cells serve as an independent T helper effector cell
subset promoting inflammation through cytokine secretion. The signature cytokines include IL-
17A, IL-17F, IL-21 and IL-22. These cytokines have stimulatory effects on B cells and activate local
inflammation and tissue damage leading subsequently to the pathogenesis of SLE [72].
3.1. role of il-17 in human slE
Statins which are used extensively in lowering cholesterol in humans have been shown to have immune-modulatory effects Current evidence suggests that SLE patients have abnormally and have recently emerged as possible therapeutic agents for high levels of IL-17 and IL-23 in their serum [75, 76] and that the autoimmune disease including SLE, although results in animal level of IL-17 correlates with disease activity [75, 77]. In a recent models have been both conflicting and controversial [82, 83]. It study Crispin et al [78] demonstrated that a significant portion was demonstrated that statins could suppress the secretion of of IL-17 in SLE patients was derived from double negative IL-17 by Th17 cells [84] and that they have beneficial effects in (DN) TCR-αβ+CD4-CD8- T cells. DN T cells represent a small improving the rate of progression of chronic kidney disease in subset in healthy individuals, whereas in the peripheral blood human SLE patients with lupus glomerulonephritis [85]. of SLE patients these cells represent a much larger component producing proinflammatory cytokines including: IL-17, IFN-γ 4. interleukin 23 (il-23)
and IL-1β [78] (see Figure 1). These DN T cells and Th17 cells IL-23 plays an important role in the development of pathogenic have also been seen in renal biopsies of patients with lupus Th17 cells and the subsequent production of IL-17 [86-88] (Figure nephritis, adding credence to their pathogenic role in renal IL-23 is a type 1 covalently linked heterodimeric cytokine As well as its direct proinflammatory activities, IL-17's effects comprising of p19 and p40 subunits, which are shared with IL- in other cell types may also contribute to SLE pathogenesis. 12 (Figure 5). IL-23 is produced in the main by both activated Dong et al [79], for example, observed that there was an increased dendritic and phagocytic cells [89, 90] and recent studies suggest production of total IgG, anti-dsDNA IgG and IL-6 by peripheral that rather than IL-12 it is the most important cytokine for the blood mononuclear cells of patients with lupus nephritis. All pathogenesis of autoimmune diseases [91, 92]. IL-23 and IL-12 of these findings indicate that IL-17 may participate in the share a common p40 subunit, which binds to a common IL- activation of B cells in patients with SLE.
12 β1 receptor (Figure 5) [94]. Activated/memory T cells, T-cell This latter finding was verified by the fact that these SLE- clones and natural killer cell lines in humans, preferentially derived B cells when cultured in the presence of IL-17 had an express the IL-23 receptor (IL-23R), which is made up of the IL- increased production of anti-DNA [79]. Evidence in regard to 23 complex, and a common IL-12 receptor β1.
the importance of this pathological mechanism in human SLE Because of its central role in the pathogenesis of various as well as the main question of whether IL-17 blockade (anti- autoimmune diseases including inflammatory bowel disease, IL-17) will be therapeutically useful for SLE patients has still to Duerr et al [95] and ankylosing spondylitis [96, 97], studies focusing be fully elucidated [80, 81]. on its role in SLE have arisen.
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Volume 25 No. 1 June2011 Figure 5: A schematic diagram of the different components making up the IL-12 and IL-23 receptors
and the common STAT4 activation pathway.
IL-12β1 and IL-12β2 each consist of three fibronectin type III and 2 cytokine receptor domains with an
additional immunoglobulin (Ig)-like domain on the latter. IL-23R closely resembles IL-12β2, however
without the fibronectin type III domains. (reproduced with permission [94]).
4.1. role of il-23 in human slE
sample size in different populations, to confirm this association [101].
As stated earlier, cytokine-mediated immunity plays an important role in the pathogenesis of SLE, and implications of 4.2. therapeutic implications of il-23 in slE
this are seen in animal models. Additionally, a number of studies in human SLE have also shown a need to focus on IL-23 and its At present the majority of the data in regard to IL-23 have come receptor. Wong et al [75], confirmed that ex vivo syntheses of IL- from studies using murine models, which may not be wholly 17 by IL-23 or IL-18 produced from co-stimulated lymphocytes relevant for human SLE. There is however growing evidence that was much higher in patients with SLE than the control group in the human model IL-23 plays a role in the development of the and increased levels of IL-12, IL-17 and Interferon-inducible disease and that the use of anti-IL-23 therapy to treat the subset protein-10 (CXCL 10) had both significant and positive of SLE patients that are characterised by high levels of IL-23 is correlations with SLEDAI [75]. It was also shown by Huang et now a distinct possibility [81]. There are two issues that need to be al [96] that in active SLE patients, the mRNA levels of p19, p40 taken cognisance of in this regard. Firstly, both IL-23 and IL-23R of PBMC were significantly higher when compared with levels are critical in mediating antimicrobial defences and in cross- in their inactive counterparts [96]. In another study, Hillyer et al regulating other cell subsets, therefore the risk of infectious [97], reported that in Rheumatoid Arthritis (RA) synovial cultures, complications need to be taken into account. Secondly most of IL-23R blockade resulted in a significant inhibition of TNF-α the data regarding IL-23 have been from murine models.
(57%), IL-1β (51%) and IL-6 (30%) [97]. All of these results Further comprehensive studies are therefore required, especially suggest that IL-23 may have pathogenic activity in a proportion in regard to the therapeutic potential of IL-23 in the treatment of the patients tested that have late-stage RA. In a recent study, Kwan et al [98] examined the urinary sediment of three groups of 5. B-lymphocyte stimulators (Blys)
subjects: those with active SLE, with history of lupus nephritis in remission, those with no history of renal involvement SLE The B-lymphocyte stimulator (BLyS also known as the B cell- and healthy individuals. In each case they quantified the mRNA activating factor belonging to the TNF family, or BAFF) [102] expression of IL-17, IL-23 and other Th 17-related cytokines. was identified as a novel TNF family ligand almost 10 years The results concluded that the urinary expression of Th-17 ago [102-105] where it was found to be the key in both the related genes was increased in the SLE patients when compared selection and survival of B cells. The expression of the BLyS to the control group. The degree of this up-regulation however, protein is confined to myeloid lineage cells (e.g. monocytes, was inversely proportional to the disease activity [98]. macrophages, dendritic cells and activated neutrophils) [106-108]. This pattern was contradictory to previous studies on the urinary Although the levels of BLyS are well established and constant, mRNA expression of Th1- and Th2-related genes [99, 100], which its expression and secretion can be increased by inflammatory showed an up-regulation of Th1-related genes and a down- cytokines, such as IL-2, TNF-α and IFN-γ [107, 109, 110]. BLyS can regulation of Th2-related genes in patients with SLE, with bind to three types of receptors: BLyS receptor 3 (also know the magnitude being proportional to overall disease activity. as BAFFR), transmembrane activator-1 and calcium modulator Although these findings suggest a regulatory role of IL-23 in the and cyclophilin ligand-interactor (TACI) and B cell maturation pathogenesis of SLE, further studies are required using a larger antigen (BCMA). It has been shown that BLyS can bind to all 10 www.smltsa.org.za ISSN 1011 5528
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Volume 25 No. 1 June 2011 these three receptors on B cells, as opposed to a proliferation- In a previous study the results showed no over-expression of inducing ligand (APRIL), which can only engage to TACI and the type I IFN gene in the blood from SLE patients whereas BCMA [111]. The most important receptor amongst the three was an over expression of several other IFN-inducible (IFI) genes found to be BAFFR as it is was the one that mediated most of have since been found [131]. This finding was in agreement with the BLyS effects.
other studies, which demonstrated that peripheral blood from SLE patients had remarkable homogeneous gene expression 5.1. implications for B cells and Blys in human slE
patterns, including an over expression of IFI genes, implying Elevated serum levels of BLyS protein have been observed in IFN involvement in SLE [132-136].
patients with autoimmune disease, including those with SLE Hopefully in the future, genetic mapping may be of assistance in and these levels correlated with their anti-dsDNA levels [112-115]. predicting the development and severity of the disease and that In one survey where the serum BLyS levels and disease activities IFN regulated cytokines may also be used to monitor disease were measured; healthy controls had normal serum BLyS levels activity and subsequent organ damage [137-138].
over time, compared to SLE patients who had escalating levels. The effect of a single dose of anti-IFN monoclonal antibody in Results displayed a persistent elevation in 25% of patients tested SLE patients was evaluated in a phase I dose-escalation study and an intermittent elevation in another 25% of patients [116]. [139]. The results noted a reduction in disease activity where the These findings suggest that BLyS may figure significantly in the over expression of IFN-inducible genes were neutralised in a development of autoimmune disease and in particular SLE, thus dose-dependent manner. In addition, a number of doses had making it an ideal target for SLE therapy.
clinical benefit in terms of SLEDAI. Currently there are two phase 2 trials taking place to evaluate the effects of anti-IFN 5.2. therapeutic implications of Blys in slE
monoclonal antibody in SLE patients [140, 141].
There are many conflicting reports regarding BLyS-targeted 7. tumour necrosis factor-a (tnf-α)
therapy using belimumab, a fully human monoclonal antibody (IgG1) that binds to BLyS and inhibits its biological activity. In a Tumour necrosis factor- alpha (TNF-α) is a proinflammatory phase I randomised controlled clinical trial [117], the safety and as well as an immunoregulatory cytokine. It is expressed as efficacy of belimumab in SLE patients was studied. Although a homotrimer on the cell surface in a soluble form after the there was a reduction in CD20+ B cells in this dose-ranging activation of macrophages and dendritic cells, (Figure 3) with study as compared to the placebo, there was no significant divergent effects on the immune system in SLE [142, 143].
improvement in disease activity as assessed by the SELENA-SLEDAI score. In a phase II dose-ranging study [118], three 7.1 role of tnf-α in human slE
different doses of bilimumab were evaluated in SLE patients who The significance of TNF-α in the pathogenesis of SLE remains were randomised over a 52 week period and again there was no controversial as one might argue that it is beneficial and that significant difference between the combined bilimumab group TNF blockade would be unfavourable. However, the in vivo versus the placebo group. A total of 71.5% of the patients were antinuclear antibody (ANA) positive and interestingly in the data ascertained from a number of SLE patients suggests the subgroup that were ANA positive the SLEDAI score was reduced by 29% at week 52. This trial was later continued as an open- The levels of TNF-α are actually increased in the serum of SLE label extension study and a four-year safety and efficacy for patients and are closely correlated with overall disease activity, [144, 145] some 237 patients has also recently been published [119] where where an abundant TNF-α expression was demonstrated serologically active patients had sustained improvement in their in lupus nephritic kidneys [146, 47].
flares over time. There was also a decline in multiple pathogenic The beneficial effects of TNF-α blocking therapy have been antibodies, including anti-dsDNA and anticardiolipin.
shown in a series of studies in patients with other autoimmune Multi-centre phase 3 trials, of Benlysta™ (belimumab) (BLISS-52 diseases, but the results were conflicting in that these patients and BLISS-76) in seropositive patients with SLE are currently developed antinuclear factors, anti-ds DNA and anticardiolipin being evaluated in two large randomised, double-blind, antibodies as well as a lupus-like syndrome [147, 148]. All symptoms placebo-controlled studies [120]. The results of these two pivotal and autoantibodies disappeared when TNF-α blocking therapy phase 3 trials, suggest that belimumab can reduce SLE disease was discontinued.
activity and that it may be the long-awaited new effective Nevertheless, the findings of elevated serum TNF-α in active therapy for this disease.
SLE and the over expression of TNF-α in active lupus nephritis [47, 149] provided the rationale for using TNF-α antagonism in SLE 6. type i interferons (type i ifn)
patients [145, 150, 151].
Although type I and type II IFNs have both been implicated Unfortunately, long term treatment using TNF-α blocking in the pathogenesis of human SLE [121-125], the type I IFNs therapy was associated with high rates of serious adverse are regarded as the most important. For example the initial reactions [152-155]. For example in two randomised trials [156, 157] symptoms in many patients with active SLE are often flu-like, that were designed to evaluate the efficacy and safety of the TNF where they exhibit symptoms such as fever and fatigue, both of inhibitors; infliximab and etanercept in SLE patients, both had which reflect high serum type I IFN levels, which is also relevant to be terminated prematurely.
to overall disease activity and severity [126-128 ].
Taking all of this recent information into consideration it is The classical triggers of type I interferon are viral DNA and RNA highly unlikely that TNF inhibition will be used routinely in the with signals being mediated via the Toll-like receptors (TLR) treatment of SLE.
or the retinoic acid inducible gene I (RIG-I) like receptors [129]. 8. concluding remarks
Although type I IFNs are manufactured by all leucocytes, the major producer is the cell subset; plasmacytoid dendritic cells This review has discussed a vast amount of information in (PDC) in response to TLR7 or TLR9 activation [130].
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Volume 25 No. 1 June2011 and SLE (Figure 6) as well as new approaches that target in achieving rapid disease control and minimise corticosteroid the pro-inflammatory cytokine pathways which lead to the use. The role of these agents in the maintenance phase of SLE amelioration of clinical disease in human SLE. However, the still remains undefined, and whether the interference of these elicited inflammatory response characterised by both the influx events becomes an important therapeutic target will depend of various cell populations mediated to a large extent by the on the results of ongoing and continuing clinical trials. Given generation of these proinflammatory cytokines still needs to the safety concerns regarding the long-term use of such agents be fully elucidated. Most of the recent trials have dealt with especially in SLE, where complications of infection and the use of agents that target the cytokines involved in this malignancy may arise, the major challenge for the future will inflammatory chain of events in the induction phase of severe be to define which one of these targets will actually be useful in disease, or in symptoms refractory to conventional treatment the management of this disease.
such as corticosteroids. They may therefore offer an advantage Figure 6: Simplified schematic diagram showing the complex interactions between various immune cells and cytokines
which lead to the pathogenesis of SLE. (reproduced with permission [9])
Holers VM. (2003). Complement receptors. In Smolen JS, Arbuckle MR, Mc Clain MT, Rubertone MV, et al. (2003). Lipsky PE eds. Targeted therapies in rheumatology. London, Development of autoantibodies before the clinical onset of New York: Martin Dunitz: 167-180.
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INTERACTION BETWEEN NK CELLS AND HLA-G1 AT THE PLACENTAL
INTERFACE OF HIV-1 INFECTED PREGNANT WOMEN: ADDITIONAL
RISK FACTORS OR PHYSIOLOGICAL ASSOCIATION?
s Moodley (phd)
Department of Biomedical Sciences, Mangosuthu University of Technology, South Africa
Grants: Support for the study was received from The National Research Funding- Thuthuka Programme and Mangosuthu University of
Technology Research Grant.
Corresponding author: Shamala Moodley email: [email protected] tel: +27 (0)31 907 7450 fax: +27 (0)31 907 7451
ABSTRACTBackground: Human Leucocyte Antigen-G (HLA-G) molecules are involved in the inhibition of cell-mediated immune responses and could promote the propagation of HIV-1 infection across the placental interface thus increasing the risk of vertical transmission. Therefore, the objective of this study was to assess whether the Major Histocompatibility Complex (MHC) - coded molecule HLA-G inhibits Natural Killer (NK) cell activity thereby, assisting viral penetration across the placental barrier in HIV-1 positive pregnant women.
Study Design & Methods: Natural Killer (CD56+) cell activity and placental HLA-G1 expression was assessed using immunohisto-chemistry and real-time polymerase chain reaction (RT-PCR) techniques, respectively. Studies were performed on a total of fifty five placental samples obtained from HIV-1 infected mothers at birth. Results: Low numbers of NK cells increased risk of vertical transmission [OR = 3.424 (95%CI 0.65-17.89)]. The risk of babies becoming infected increased by 1.3 with every 1 unit increase in HLA-G1 expression. A positive correlation was observed between mothers' log viral load and transmission of infection to the baby (p = 0.047; 95%CI 1.029-11.499). Conclusion: Low NK cell activity at the placental interface increased the risk of vertical transmission. Maternal viral load remained a strong predictor of viral transmission. KEYWORDSNatural Killer cells (CD56+), Human Leucocyte Antigen-G1, vertical transmission, viral load, up regulation.
Natural Killer (NK) cells are a population of low-density, large against certain microbial, viral and parasitic infections [1, 2]. In granular lymphocytes, which mainly develop and differenti- response to proinflammatory stimuli, which may be induced by ate in bone marrow and then enter into the circulation. These a viral infection, NK cells migrate to various tissues and organs cells comprise approximately 5-20% of peripheral blood of the body. In the mucosal decidual tissues of the maternal lymphocytes and are involved in the innate immune response uterus, NK cells are the most abundant class of lymphocyte, ISSN 1011 5528 www.smltsa.org.za 17

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