Autoantibody to CD40 ligand in systemic lupus erythematosus: association with thrombocytopenia but not thromboembolism

Systemic lupus erythematosus-complicating immune thrombocytopenia: From pathogenesis to treatment

Immune thrombocytopenia (ITP) is a common hematological manifestation of systemic lupus erythematosus (SLE). The heterogeneity of its clinical characteristics and therapeutic responses reflects a complex pathogenesis. A better understanding of its pathophysiological mechanisms and employing an optimal treatment regimen is therefore important to improve the response rate and prognosis, and avoid unwanted outcomes. Besides glucocorticoids, traditional immunosuppressants (i.e. cyclosporine, mycophenolate mofetil) and intravenous immunoglobulins, new therapies are emerging and promising for the treatment of intractable SLE-ITP, such as thrombopoietin receptor agonists (TPO-RAs), platelet desialylation inhibitors(i.e. oseltamivir), B-cell targeting therapy(i.e. rituximab, belimumab), neonatal Fc receptor(FcRn) inhibitor, spleen tyrosine kinase(Syk) inhibitor and Bruton tyrosine kinase(BTK) inhibitor et al., although more rigorous randomized controlled trials are needed to substantiate their efficacy. In this review, we update our current knowledge on the pathogenesis and treatment of SLE-ITP.

Platelets as Key Factors in Inflammation: Focus on CD40L/CD40

Platelets are anucleate cytoplasmic fragments derived from the fragmentation of medullary megakaryocytes. Activated platelets adhere to the damaged endothelium by means of glycoproteins on their surface, forming the platelet plug. Activated platelets can also secrete the contents of their granules, notably the growth factors contained in the α-granules, which are involved in platelet aggregation and maintain endothelial activation, but also contribute to vascular repair and angiogenesis. Platelets also have a major inflammatory and immune function in antibacterial defence, essentially through their Toll-like Receptors (TLRs) and Sialic acid-binding immunoglobulin-type lectin (SIGLEC). Platelet activation also contributes to the extensive release of anti- or pro-inflammatory mediators such as IL-1β, RANTES (Regulated on Activation, Normal T Expressed and Secreted) or CD154, also known as the CD40-ligand. Platelets are involved in the direct activation of immune cells, polynuclear neutrophils (PNNs) and dendritic cells via the CD40L/CD40 complex. As a general rule, all of the studies presented in this review show that platelets are capable of covering most of the stages of inflammation, primarily through the CD40L/CD40 interaction, thus confirming their own role in this pathophysiological condition.

Immune Thrombocytopenia in Antiphospholipid Syndrome: Is It Primary or Secondary?

Antiphospholipid syndrome (APS) is frequently associated with thrombocytopenia, in most cases mild and in the absence of major bleedings. In some patients with a confirmed APS diagnosis, secondary immune thrombocytopenia (ITP) may lead to severe thrombocytopenia with consequent major bleeding. At the same time, the presence of antiphospholipid antibodies (aPL) in patients with a diagnosis of primary ITP has been reported in several studies, although with some specific characteristics especially related to the variety of antigenic targets. Even though it does not enter the APS defining criteria, thrombocytopenia should be regarded as a warning sign of a “high risk” APS and thus thoroughly evaluated. The presence of aPL in patients with ITP should be assessed as well to stratify the risk of paradoxical thrombosis. In detail, besides the high hemorrhagic risk in secondary thrombocytopenia, patients with a co-diagnosis of APS or only antibodies are also at risk of arterial and venous thrombosis. In this narrative review, we discuss the correlation between APS and ITP, the mechanisms behind the above-reported entities, in order to support clinicians to define the most appropriate treatment strategy in these patients, especially when anticoagulant or antiplatelet agents may be needed.

Targeting the CD40-CD154 Signaling Pathway for Treatment of Autoimmune Arthritis

Full activation of T lymphocytes requires signals from both T cell receptors and costimulatory molecules. In addition to CD28, several T cell molecules could deliver costimulatory signals, including CD154, which primarily interacts with CD40 on B-cells. CD40 is a critical molecule regulating several B-cell functions, such as antibody production, germinal center formation and cellular proliferation. Upregulated expression of CD40 and CD154 occurs in immune effector cells and non-immune cells in different autoimmune diseases. In addition, therapeutic benefits have been observed by blocking the CD40-CD154 interaction in animals with collagen-induced arthritis. Given the therapeutic success of the biologics abatacept, which blocks CD28 costimulation, and rituximab, which deletes B cells in the treatment of autoimmune arthritis, the inhibition of the CD40-CD154 axis has two advantages, namely, attenuating CD154-mediated T cell costimulation and suppressing CD40-mediated B-cell stimulation. Furthermore, blockade of the CD40-CD154 interaction drives the conversion of CD4+ T cells to regulatory T cells that mediate immunosuppression. Currently, several biological products targeting the CD40-CD154 axis have been developed and are undergoing early phase clinical trials with encouraging success in several autoimmune disorders, including autoimmune arthritis. This review addresses the roles of the CD40-CD154 axis in the pathogenesis of autoimmune arthritis and its potential as a therapeutic target.

Biologics in the Treatment of Lupus Erythematosus: A Critical Literature Review

Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disease affecting multiple organ systems that runs an unpredictable course and may present with a wide variety of clinical manifestations. Advances in treatment over the last decades, such as use of corticosteroids and conventional immunosuppressive drugs, have improved life expectancy of SLE sufferers. Unfortunately, in many cases effective management of SLE is still related to severe drug-induced toxicity and contributes to organ function deterioration and infective complications, particularly among patients with refractory disease and/or lupus nephritis. Consequently, there is an unmet need for drugs with a better efficacy and safety profile. A range of different biologic agents have been proposed and subjected to clinical trials, particularly dedicated to this subset of patients whose disease is inadequately controlled by conventional treatment regimes. Unfortunately, most of these trials have given unsatisfactory results, with belimumab being the only targeted therapy approved for the treatment of SLE so far. Despite these pitfalls, several novel biologic agents targeting B cells, T cells, or cytokines are constantly being evaluated in clinical trials. It seems that they may enhance the therapeutic efficacy when combined with standard therapies. These efforts raise the hope that novel drugs for patients with refractory SLE may be available in the near future. This article reviews the current biological therapies being tested in the treatment of SLE.

Update on clinical trials in systemic lupus erythematosus

PURPOSE OF REVIEW

With advancement in our understanding of pathogenic mechanisms in systemic lupus erythematosus (SLE), there is tremendous enthusiasm in examining drugs, old and new, to improve outcomes. This review highlights recent trials' successes and impasses that have come to fore.

RECENT FINDINGS

Among B-cell therapies, belimumab continues its run of successes with sustained safety and tolerability documented in a long-term extension as well as the likely approval of a subcutaneous formulation in the near future. With greater antibody-dependent cytotoxicity and less immunogenicity, there is hope for obinituzumab to succeed where its anti-CD 20 predecessors have failed. Drugs targeting type I interferons - sifalimumab and anifrolumab - have been efficacious albeit with an increase in incidence of Herpes zoster infections. There is also renewed interest in evaluating the efficacy of calcineurin inhibitors, specifically tacrolimus in the induction and maintenance of lupus nephritis. Introspection into clinical trial designs have highlighted the effects of entry criteria, end points, background medications and geographical differences on study outcomes.

SUMMARY

There are at least 50 drugs and targets being evaluated in SLE. In addition to developing new drugs to treat lupus, future trials have to focus on more effective study designs to improve chances of trial success.

Lupus thrombocytopenia: pathogenesis and therapeutic implications

Systemic Lupus Erythematosus (SLE) is frequently complicated by cytopenias. Thrombocytopenia is usually non severe and its frequency ranges from 20% to 40%. It is mostly an autoimmune process caused by autoantibodies against platelet surface glycoproteins and it is associated with worse prognosis in SLE. It can also be a result of SLE treatment with azathioprine, methotrexate and rarely hydroxychloroquine or thrombotic microangiopathy or macrophage activation syndrome. If thrombocytopenia is mild (>50×10⁹/L) and there is no other evidence of disease there is no need of therapy. Severe thrombocytopenia is less frequent and needs therapeutic management. Corticosteroids are the cornerstone of therapy. Continuous high dose oral prednisolone or pulse high dose methylprednisolone (MP) with or without intravenous immune globulin are used in the acute phase. Second line agents (hydroxychloroquine, danazol, azathioprine, cyclosporine, mycophenolate mofetil, cyclophosphamide, rituximab) are usually needed. Splenectomy is indicated for recurrent or resistant cases. There are no evidence-based guidelines to facilitate selection of one drug over another but certainly the co-existence of other systemic SLE manifestations must be taken into account. Newer therapies are emerging although there is no consensus on the treatment of refractory lupus thrombocytopenia due to the absence of controlled randomized trials.

Bone Marrow Megakaryocytes May Predict Therapeutic Response of Severe Thrombocytopenia in Patients with Systemic Lupus Erythematosus

Objective.

To analyze the predictive value of megakaryocyte counts in bone marrow (BM-MK) for determining the therapeutic response of severe thrombocytopenia (TP) in patients with systemic lupus erythematosus (SLE).

Methods.

Thirty-five patients with SLE with severe TP (platelet count ≤ 50 × 109/l) from the Peking Union Medical College Hospital admitted between 2007 and 2014 with appreciable bone marrow aspiration results were analyzed retrospectively. The associations between therapeutic response and clinical manifestations, laboratory findings including BM-MK counts, were evaluated.

Results.

Seventeen (49%) and 8 (23%) patients achieved a complete response (CR) and a partial response (PR), respectively, and 10 had no response (NR). The BM-MK counts in each group were 102 ± 25 (0–322), 136 ± 48 (2–419), and 28 ± 12 (0–105) per slide, respectively. Significant differences were observed in the counts of BM-MK between patients who achieved a clinical response (CR + PR) and those who did not (NR; p = 0.007). Patients in the NR group exhibited fewer BM-MK compared with those in the CR and PR groups (p = 0.017 and p = 0.006, respectively). A receiver-operation characteristic analysis identified that a cutoff value of BM-MK counts at 20 performed pretty well in discriminating patients with differential responses to immunotherapy, with sensitivity and specificity and area under the curve of 88%, 70%, and 0.798, respectively.

Conclusion.

BM-MK count may serve as a good predicting factor for immunotherapeutic response in patients with SLE with severe TP. Patients with BM-MK counts < 20 per slide tend to exhibit poor clinical response.

The significance and management of thrombocytopenia in antiphospholipid syndrome

The association between antiphospholipid antibodies (aPL) and clinical problems goes beyond what is stated in the antiphospholipid syndrome (APS) classification criteria, namely thrombosis and pregnancy morbidity, and thrombocytopenia is the most common non-criteria hematologic manifestation of aPL with a frequency ranging from 20 to 50 %. Thrombocytopenia is rarely severe, and hemorrhage is far less common than thrombosis. However, when anticoagulation is considered, it may constitute a clinical problem with increased bleeding risk. Furthermore, thrombocytopenia represents a risk factor for thrombosis in aPL-positive patients. Therefore, it is important to understand the pathogenesis and the clinical associations of thrombocytopenia to build the right medical approach in aPL-positive patients. In this paper, we review the literature on aPL/APS-associated thrombocytopenia and briefly discuss the other conditions that can result in thrombocytopenia as they have commonalities with APS and their recognition is important to establish the most appropriate treatment strategy.

The CD40/CD40L system: a new therapeutic target for disease

The role of CD40/CD40 ligand (CD40L) interactions in atherothrombosis, in the response of the immune system to pathogens and in thrombosis is now widely accepted. A role for CD40-CD40L interactions has been identified in atherosclerosis (AS), and such interactions are known to destabilize atherosclerotic plaques by inducing the expression of cytokines, chemokines, growth factors, matrix metalloproteinases and pro-coagulant factors. CD40/CD40L interactions have also been implicated in immune system disorders. Recent studies have suggested that CD40/CD40L interactions regulate oxidative stress and affect various signaling pathways in both the immunological and the cardiovascular systems. Here, we discuss the current drugs that target the CD40/CD40L system, as understanding the roles and regulations of CD40/CD40L-mediated signal pathways by these drugs could facilitate the development of therapeutics that target diverse diseases.

Immunosuppressive monoclonal antibodies: current and next generation

Monoclonal antibodies (mAbs) are well-established therapeutics, as evidenced by the large number of Food and Drug Administration-approved mAbs for the treatment of cancers, and inflammatory or autoimmune diseases, and for the prevention and treatment of solid organ transplant rejection. Although, in many cases, mAbs have improved patient survival, they are also associated with an increased incidence of opportunistic infections. We review here the current and next generation of mAbs and the risks that infectious disease specialists should be aware of.

The ITP syndrome: pathogenic and clinical diversity

Immune thrombocytopenia (ITP) is mediated by platelet autoantibodies that accelerate platelet destruction and inhibit their production. Most cases are considered idiopathic, whereas others are secondary to coexisting conditions. Insights from secondary forms suggest that the proclivity to develop platelet-reactive antibodies arises through diverse mechanisms. Variability in natural history and response to therapy suggests that primary ITP is also heterogeneous. Certain cases may be secondary to persistent, sometimes inapparent, infections, accompanied by coexisting antibodies that influence outcome. Alternatively, underlying immune deficiencies may emerge. In addition, environmental and genetic factors may impact platelet turnover, propensity to bleed, and response to ITP-directed therapy. We review the pathophysiology of several common secondary forms of ITP. We suggest that primary ITP is also best thought of as an autoimmune syndrome. Better understanding of pathogenesis and tolerance checkpoint defects leading to autoantibody formation may facilitate patient-specific approaches to diagnosis and management.

A CD40-CD154 interaction in tissue fibrosis

OBJECTIVE

To examine the role of an interaction between fibroblasts and mononuclear infiltrates through CD40-CD154 engagement in the development of tissue fibrosis.

METHODS

Cultured dermal fibroblasts derived from healthy skin were induced to express CD40 by adenoviral gene transfer, stimulated with soluble CD154, and evaluated for proliferation, gene expression, and protein expression in vitro. The skin of mice with bleomycin-induced skin sclerosis, a model for systemic sclerosis (SSc), was assessed for CD40 and CD154 expression, in vivo fibroblast proliferation, and the expression of specific genes. The effects of an anti-CD154 monoclonal antibody on bleomycin-induced skin sclerosis were also examined.

RESULTS

Upon stimulation with soluble CD154, cultured fibroblasts induced to express CD40 by adenoviral gene transfer proliferated and showed up-regulation of the genes for intercellular adhesion molecule 1, interleukin-6 (IL-6), IL-8, monocyte chemoattractant protein 1 (MCP-1), and RANTES, as well as up-regulation of their proteins. In the skin from bleomycin-treated mice, dermal fibroblasts expressed CD40, and mast cells and CD4+ T cells expressed CD154. Electron microscopic analysis revealed fibroblasts attached to mast cells and T cells with primitive contacts. The proliferation of fibroblasts and the up-regulated MCP-1 gene expression preceded thickening of the dermis. Finally, the anti-CD154 antibody inhibited the bleomycin-induced skin sclerosis by suppressing fibroblast proliferation and down-regulating MCP-1 expression.

CONCLUSION

The interaction between fibroblasts and mast cells or T cells through CD40-CD154 signaling is critical for fibroblast activation early in the course of fibrosis. Blockade of the CD40-CD154 signal may be a novel therapeutic strategy for human fibrotic diseases, such as SSc.

T-cell costimulation and coinhibition in atherosclerosis

Evidence from many human and rodent studies has established that T lymphocytes enhance inflammation in atherosclerotic plaques and contribute to lesion progression and remodeling. Recent work also indicates that regulatory T cells are important in limiting proatherogenic T-cell responses. Given the important role of T cells in atherosclerosis, there is a need to fully understand how proatherogenic T cells are activated and regulated. Antigen-dependent activation of naïve T cells, leading to clonal expansion and effector T-cell differentiation, and effector and memory T cells, is enhanced by signals provided by costimulatory molecules expressed by antigen presenting cells, which bind to receptors on the T cells. In addition, T-cell responses to antigen are negatively regulated by coinhibitory molecules expressed by antigen-presenting cells, which bind to receptors on T cells. Two major families of costimulatory molecules include the B7 and the tumor necrosis factor (TNF) families. These molecules bind to receptors on T cells belonging to the CD28 or TNF receptor families, respectively. The best-defined coinhibitors and their receptors belong to the B7 and CD28 families. Recent work has begun to define how these T-cell costimulatory and coinhibitory pathways influence atherosclerosis, largely in mouse models of the disease. Profound effects are attributable to molecules in both the B7/CD28 (B7-1/2, ICOS, and PDL-1/2) and the TNF/TNF receptor (CD40, OX40, and CD137) families. One emerging theme is that both pathogenic effector T-cell responses and regulatory T cells are influenced by overlapping sets of costimulators and coinhibitors. These complexities must be considered as immunotherapeutic approaches for atherosclerotic disease are developed.

Modulating co-stimulation

The modulation of co-stimulatory pathways represents a novel therapeutic strategy to regulate autoimmune diseases. Auto-reactive CD4+ T cells play a critical role in initiating the immune response leading to inflammation and autoimmune diseases. Blocking co-stimulatory signals prevents T-cell activation, thus diminishing autoimmune responses and possibly preventing the progression of autoimmune disease. Blockade of several co-stimulatory pathways has been investigated in animal models and has led to clinical trials testing specific blocking agents in humans. In this review we will describe the role of co-stimulatory pathways, primarily the CD28-B7 pathway, in autoimmune diseases, and we will present in vivo and in vitro studies supporting the efficacy of co-stimulation blockade in animal models of autoimmune disease. Finally, we will discuss the clinical therapeutic efficacy of blocking monoclonal antibodies in preventing or reducing auto-antigen driven T-cell activation in humans with particular attention to the CD28/B7 pathway. Inhibiting co-stimulatory molecule interactions by using monoclonal antibodies seems to be an original approach to regulate autoimmune diseases in humans.

Excessive exposure to anionic surfaces maintains autoantibody response to beta(2)-glycoprotein I in patients with antiphospholipid syndrome

Antiphospholipid syndrome (APS) is an autoimmune prothrombotic disorder associated with autoantibodies to phospholipid (PL)-binding proteins, such as beta(2)-glycoprotein I (beta(2)GPI). We have recently reported that binding of beta(2)GPI to anionic PL facilitates processing and presentation of the cryptic beta(2)GPI epitope that activates pathogenic autoreactive T cells. To clarify mechanisms that induce sustained presentation of the dominant antigenic beta(2)GPI determinant in patients with APS, T-cell proliferation induced by beta(2)GPI-treated phosphatidylserine liposome (beta(2)GPI/PS) was evaluated in bulk peripheral blood mononuclear cell cultures. T cells from patients with APS responded to beta(2)GPI/PS in the presence of immunoglobulin G (IgG) anti-beta(2)GPI antibodies derived from APS plasma, and this response was completely inhibited either by the depletion of monocytes or by the addition of anti-FcgammaRI antibody. These findings indicate that efficient presentation of the cryptic determinants can be achieved by monocytes undergoing FcgammaRI-mediated uptake of beta(2)GPI-bound anionic surfaces in the presence of IgG anti-beta(2)GPI antibodies. Finally, beta(2)GPI-bound oxidized LDL or activated platelets also induced the specific T-cell response. Continuous exposure to these anionic surfaces may play a critical role in maintaining the pathogenic anti-beta(2)GPI antibody response in patients with APS.

Notes on the kidney and its diseases for the neurologist

To save their patients from dialysis and transplantation, neurologists need simply remain alert to the possibility of renal failure, particularly in the context of systemic disease, diabetes, sepsis and drugs. Of the numerous territories shared by our respective specialities, we outline a pragmatic approach to the diagnosis and treatment of the vasculitides, underpinned by knowing which questions to ask, equally importantly when to ask them, and in the art of obtaining a tissue diagnosis. We consider the current evolving trial evidence that directs the usage of a growing arsenal of therapies in the induction and maintenance stages of vasculitis treatment, and extend this consideration to Lupus and Sjogren's.

Prevalence of secondary hematologic disorders in the antiphospholipid syndrome: impact on coagulation risk

Hematologic abnormalities may occur in antiphospholipid antibody syndrome. The most common of these abnormalities is thrombocytopenia. The mechanism by which low platelet counts occur is not known but studies continue to elucidate the potential role of autoantibodies and cell surface markers. The risk for thrombosis in patients with thrombocytopenia does not appear to be related to the presence of thrombocytopenia itself. Innovative treatment with anti-CD20 antibodies may be of benefit in reversing thrombocytopenia and treatment with splenectomy does not appear to increase the risk for subsequent thrombosis. Hemolytic anemia is associated with antiphospholipid antibodies as well, but the risk for thrombosis in patients with hemolytic anemia is not clearly elevated. Diagnostic features of disseminated intravascular coagulation may co-occur with the antiphospholipid syndrome and may be associated with a catastrophic clinical presentation.