Prognostic significance of platelet count in SLE patients

Association of inflammatory biomarkers with overall survival in burn patients: a systematic review and meta-analysis

INTRODUCTION

The inflammatory response to burn injuries can lead to organ dysfunction that ultimately results in increased mortality and morbidity. This meta-analysis was conducted to determine the efficacy of inflammatory biomarkers, including the neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), procalcitonin (PCT), and C-reactive protein (CRP) as predictive tools of mortality among burn patients.

MATERIAL AND METHODS

The biomarker levels of survivors and non-survivors were consolidated according to guidelines for Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Three main databases were searched electronically: PubMed, Web of Science, and Scopus, on December 8, 2022. The Newcastle-Ottawa Quality Assessment Scale (NOS) was used to evaluate and score the methodological quality of the included studies. The standard mean difference (SMD) with a 95% confidence interval (CI) was utilized.

RESULTS

Twenty-four studies were included in our systematic review and meta-analysis, (3636 total burn patients), of whom 2878 survived. We found that deceased burn patients had elevated levels of NLR (SMD = 0.60, 95% CI; 0.19-1.00, P < 0.001), CRP (SMD = 0.80, 95% CI; 0.02-1.58, P = 0.04), and PCT (SMD = 0.85, 95% CI; 0.45-1.24, P < 0.001), compared to survivors. However, we found no association between PLR and mortality among burn patients (SMD = 0.00, 95% CI; -0.14-0.15, P < 0.001). In addition, CRP was significantly higher in non-survivors (SMD = 0.80, 95% CI; 0.02-1.58, P =0.04). Similar results were also found about PCT (SMD = 0.85, 95% CI; 0.45-1.24, P < 0.001). When we analyzed the PCT data, collected in the first 24-48 hours, we found similar results; the PCT level was significantly higher in non-survivors in the immediate postinjury-period (SMD = 0.67, 95% CI; 0.31-1.02, P < 0.001). There was no publication bias among studies on the role of NLR in burn (Egger's test P = 0.91). The based cut-off values for NLR (13), CRP (71), and PCT (1.77) yielded sensitivities of 69.2%, 100%, and 93.33%, and specificities of 76%, 72.22%, and 72.22% respectively.

DISCUSSION/CONCLUSIONS

PCT is a marker of sepsis, therefore its elevated level is presumably associated with a higher incidence and severity of sepsis among non-survivors. In addition, NLR and CRP are promising biomarkers for predicting and guiding prevention against burn deaths in clinical settings.

Serum levels of CXCL5 are decreased and correlate with circulating platelet counts in systemic lupus erythematosus

OBJECTIVE

To identify disease-specific serum chemokine profiles and potential anti-inflammatory chemokines in three rheumatic diseases.

METHODS

The discovery cohort included 18 patients with rheumatoid arthritis (RA), 20 patients with primary Sjögren's syndrome (pSS), 24 patients with systemic lupus erythematosus (SLE) and 28 healthy subjects. Findings from the discovery cohort were validated in two replication cohorts, consisting of 23 patients with SLE matched with 23 healthy subjects and 62 patients with SLE, 16 patients with ANCA-associated vasculitis (AAV), and 32 healthy controls, respectively. Serum levels of chemokines were determined using multiplex assay or ELISA.

RESULTS

In the discovery cohort, serum levels of multiple chemokines were increased in one or more diseases in comparison to healthy subjects, including CCL2, CCL20, CXCL9, CXCL10, and CXCL11 in SLE, CCL2, CCL4, and CXCL11 in pSS, and CCL2, CCL4, and CXCL9 in RA. Notably, serum levels of CCL3 (p = .0003) and CXCL5 (p = .0003) were decreased in SLE. The SLE-specific decrease in CXCL5 serum levels was confirmed in the two replication cohorts, with p = .0034 and p = .0006, respectively. Moreover, a positive correlation between serum levels of CXCL5 and circulating platelet counts (R = .71, p = .00018) in SLE observed in the discovery cohort was confirmed in both replication cohorts (R = .52, p = .011 and R = .49, p = .00005, respectively).

CONCLUSION

In the present study, we demonstrate that serum levels of CXCL5 are decreased in patients with SLE and positively correlated with circulating platelet count. These findings suggest that platelet-associated CXCL5 is presumably involved in the development of SLE.

Functional autoantibodies: Definition, mechanisms, origin and contributions to autoimmune and non-autoimmune disorders

A growing body of evidence underscores the relevance of functional autoantibodies in the development of various pathogenic conditions but also in the regulation of homeostasis. However, the definition of functional autoantibodies varies among studies and a comprehensive overview on this emerging topic is missing. Here, we do not only explain functional autoantibodies but also summarize the mechanisms underlying the effect of such autoantibodies including receptor activation or blockade, induction of receptor internalization, neutralization of ligands or other soluble extracellular antigens, and disruption of protein-protein interactions. In addition, in this review article we discuss potential triggers of production of functional autoantibodies, including infections, immune deficiency and tumor development. Finally, we describe the contribution of functional autoantibodies to autoimmune diseases including autoimmune thyroid diseases, myasthenia gravis, autoimmune pulmonary alveolar proteinosis, autoimmune autonomic ganglionopathy, pure red cell aplasia, autoimmune encephalitis, pemphigus, acquired thrombotic thrombocytopenic purpura, idiopathic dilated cardiomyopathy and systemic sclerosis, as well as non-autoimmune disorders such as allograft rejection, infectious diseases and asthma.

Searching for a prognostic index in lupus nephritis

BACKGROUND

Currently we do not have an ideal biomarker in lupus nephritis (LN) that should help us to identify those patients with SLE at risk of developing LN or to determine those patients at risk of renal progression. We aimed to evaluate the development of a prognostic index for LN, through the evaluation of clinical, analytical and histological factors used in a cohort of lupus. We have proposed to determine which factors, 6 months after the diagnosis of LN, could help us to define which patients will have a worse evolution of the disease and may be, more aggressive treatment and closer follow-up.

METHODS

A retrospective study to identify prognostic factors was carried out. We have included patients over 18 years of age with a clinical diagnosis of systemic lupus erythematosus (SLE) and kidney involvement confirmed by biopsy, who are followed up in our centre during the last 20 years. A multi-step statistical approach will be used in order to obtain a limited set of parameters, optimally selected and weighted, that show a satisfactory ability to discriminate between patients with different levels of prognosis.

RESULTS

We analysed 92 patients with LN, although only 73 have been able to be classified according to whether or not they have presented poor renal evolution. The age of onset (44 vs. 32; p = 0.024), the value of serum creatinine (1.41 vs. 1.04; p = 0.041), greater frequency of thrombocytopenia (30 vs. 7%; p = 0.038), higher score in the renal chronicity index (2.47 vs. 1.04; p = 0.015), proliferative histological type (100%) and higher frequency of interstitial fibrosis (67 vs. 32%; p = 0.017) and tubular atrophy (67 vs. 32%; p = 0.018) was observed between two groups. The multivariate analysis allowed us to select the best predictive model for poor outcome at 6 months based on different adjustment and discrimination parameters.

CONCLUSION

We have developed a prognostic index of poor renal evolution in patients with LN that combines demographic, clinical, analytical and histopathological factors, easy to use in routine clinical practice and that could be an effective tool in the early detection and management.

Treatment of congenital thrombocytopenia and decreased collagen reactivity in G6b-B-deficient mice

Mice lacking the immunoreceptor tyrosine-based inhibition motif-containing co-inhibitory receptor G6b-B (Mpig6b, G6b knockout, KO) are born with a complex megakaryocyte (MK) per platelet phenotype, characterized by severe macrothrombocytopenia, expansion of the MK population, and focal myelofibrosis in the bone marrow and spleen. Platelets are almost completely devoid of the glycoprotein VI (GPVI)-FcRγ-chain collagen receptor complex, have reduced collagen integrin α2β1, elevated Syk tyrosine kinase activity, and a subset has increased surface immunoglobulins. A similar phenotype was recently reported in patients with null and loss-of-function mutations in MPIG6B. To better understand the cause and treatment of this pathology, we used pharmacological- and genetic-based approaches to rescue platelet counts and function in G6b KO mice. Intravenous immunoglobulin resulted in a transient partial recovery of platelet counts, whereas immune deficiency did not affect platelet counts or receptor expression in G6b KO mice. Syk loss-of-function (R41A) rescued macrothrombocytopenia, GPVI and α2β1 expression in G6b KO mice, whereas treatment with the Syk kinase inhibitor BI1002494 partially rescued platelet count but had no effect on GPVI and α2β1 expression or bleeding. The Src family kinase inhibitor dasatinib was not beneficial in G6b KO mice. In contrast, treatment with the thrombopoietin mimetic romiplostim rescued thrombocytopenia, GPVI expression, and platelet reactivity to collagen, suggesting that it may be a promising therapeutic option for patients lacking functional G6b-B. Intriguingly, GPVI and α2β1 expression were significantly downregulated in romiplostim-treated wild-type mice, whereas GPVI was upregulated in romiplostim-treated G6b KO mice, suggesting a cell intrinsic feedback mechanism that autoregulates platelet reactivity depending on physiological needs.

The Screening of Fixation-Related Infection in Patients Undergoing Conversion Total Hip Arthroplasty after Failed Internal Fixation of Hip Fractures: A Single-Central Retrospective Study

Objective

To evaluate the diagnostic values of preoperative plasma fibrinogen and platelet count for screening fixation‐related infection (FRI) in patients undergoing conversion total hip arthroplasty (cTHA) after failed internal fixation of hip fractures.

Method

This was a single‐center retrospective study. Data were retrospectively analyzed for 435 patients who underwent cTHA in our hospital from January 2008 to September 2020. They were divided into infected (n = 30) and non‐infected groups (n = 405) according to the 2013 International Consensus Meeting (ICM) criteria. The diagnostic sensitivity and specificity of plasma fibrinogen and platelet count were determined using receiver operating characteristic (ROC) curves. Optimal predictive cutoffs of these two markers were determined based on the Youden index. In addition, the diagnostic value of preoperative serum C‐reactive protein (CRP) and erythrocyte sedimentation rate (ESR) for screening FRI were also evaluated based on the cutoffs recommended by the 2013 ICM Criteria. Finally, the diagnostic ability of various combinations of the plasma fibrinogen and platelet count as well as serum CRP and ESR was re‐assessed.

Results

The numbers of patients with and without FRI were 30 (6.9%) and 405 (93.1%), respectively. Areas under the ROC curves were 0.770 for fibrinogen, 0.606 for platelet, 0.844 for CRP and 0.749 for ESR. The optimal predictive cutoff of fibrinogen was 3.73 g/L, which gave sensitivity of 60.0% and specificity of 90.5%. The optimal predictive cutoff for platelet was 241.5 × 10⁹/L, which gave sensitivity of 46.7% and specificity of 83.7%. The CRP gave sensitivity of 66.7% and specificity of 92.5% with the predetermined cutoff of 10 mg/L, while the ESR gave sensitivity of 67.5% and specificity of 72.4% % with the predetermined cutoff of 30 mm/h. The combination of CRP and ESR showed high specificity of 93.2% but low sensitivity of 66.7%, while the corresponding values for CRP with fibrinogen were satisfied both for sensitivity of 80.0% and specificity of 78.7%. The combination of these four biomarkers gave sensitivity of 73.3% and specificity of 85.7%.

Conclusion

Preoperative serum CRP, ESR, plasma fibrinogen and platelet count have low sensitivity on their own for screening FRI in patients, but the combination of CRP with fibrinogen shows promise for that.

Neutrophil to lymphocyte ratio and platelet to lymphocyte ratio reflect disease activity and flares in patients with systemic lupus erythematosus - A prospective study

OBJECTIVES

To determine the association between neutrophil to lymphocyte ratio (NLR) and platelet to lymphocyte ratio (PLR) with disease activity and flares in an inception cohort of patients with systemic lupus erythematosus (SLE) using a prospective study design.

METHODS

Consecutive adult patients (age≥21) who fulfilled the 1997 American College of Rheumatology (ACR) or the 2012 Systemic Lupus International Collaboration Clinic Classification (SLICC) Criteria for SLE were followed every 3 months, with SLE disease activity assessed by using SLEDAI-2K, and disease flares defined and captured by the SELENA-SLEDAI Flare Index (SFI). NLR and PLR were computed from the automated machine-counted blood count differentials. Linear mixed model and generalized estimating equation model were constructed to analyze the associations between NLR/PLR and SLEDAI-2K and disease flares, with multivariate adjustments.

RESULTS

Of 290 patients recruited, the median (IQR) duration of follow-up and baseline SLEDAI-2K were 4.7 (3.2-6.1) years and 2 (0.5-3.5), respectively. On multivariable analyses, NLR was shown to be positively and significantly associated with SLEDAI-2K (estimate of coefficient (β)=0.05, P<0.01) and severe disease flares (odds ratio [OR] 1.05, P<0.05), but not with overall disease flares [OR 1.02, non-significant]. While PLR was shown to be positively associated with SLEDAI-2K [β=0.09, P<0.05], no statistically significant association between PLR and overall or severe disease flares was found [OR 1.00 and OR 1.06 respectively, non-significant].

CONCLUSION

Derived readily from automated blood count differentials, the NLR potentially serves as a surrogate prospective marker of disease activity and severe disease flares in SLE patients.

Platelet Activation Mechanisms and Consequences of Immune Thrombocytopenia

Autoimmune disorders are often associated with low platelet count or thrombocytopenia. In immune-induced thrombocytopenia (IIT), a common mechanism is increased platelet activity, which can have an increased risk of thrombosis. In addition, or alternatively, auto-antibodies suppress platelet formation or augment platelet clearance. Effects of the auto-antibodies are linked to the unique structural and functional characteristics of platelets. Conversely, prior platelet activation may contribute to the innate and adaptive immune responses. Extensive interplay between platelets, coagulation and complement activation processes may aggravate the pathology. Here, we present an overview of the reported molecular causes and consequences of IIT in the most common forms of autoimmune disorders. These include idiopathic thrombocytopenic purpura (ITP), systemic lupus erythematosus (SLE), antiphospholipid syndrome (APS), drug-induced thrombocytopenia (DITP), heparin-induced thrombocytopenia (HIT), COVID-19 vaccine-induced thrombosis with thrombocytopenia (VITT), thrombotic thrombocytopenia purpura (TTP), and hemolysis, the elevated liver enzymes and low platelet (HELLP) syndrome. We focus on the platelet receptors that bind auto-antibodies, the immune complexes, damage-associated molecular patterns (DAMPs) and complement factors. In addition, we review how circulating platelets serve as a reservoir of immunomodulatory molecules. By this update on the molecular mechanisms and the roles of platelets in the pathogenesis of autoimmune diseases, we highlight platelet-based pathways that can predispose for thrombocytopenia and are linked thrombotic or bleeding events.

Pathogenic mechanisms contributing to thrombocytopenia in patients with systemic lupus erythematosus

SummarySystemic lupus erythematosus (SLE) is an autoimmune condition developing thrombocytopenia in about 10-15% of cases, however, mechanisms leading to low platelet count were not deeply investigated in this illness. Here we studied possible causes of thrombocytopenia, including different mechanisms of platelet clearance and impairment in platelet production. Twenty-five SLE patients with and without thrombocytopenia were included. Platelet apoptosis, assessed by measurement of loss of mitochondrial membrane potential, active caspase 3 and phosphatidylserine exposure, was found to increase in thrombocytopenic patients. Plasma from 67% SLE patients (thrombocytopenic and non-thrombocytopenic) induced loss of sialic acid (Ricinus communis agglutinin I and/or Peanut agglutinin binding) from normal platelet glycoproteins. Concerning platelet production, SLE plasma increased megakaryopoiesis (evaluated using normal human cord blood CD34+ hematopoietic progenitors), but inhibited thrombopoiesis (proplatelet count). Anti-platelet autoantibody depletion from SLE plasma reverted this inhibition. Overall, abnormalities were more frequently observed in thrombocytopenic than non-thrombocytopenic SLE patients and in those with active disease (SLEDAI≥5). In conclusion, platelet clearance due to apoptosis and desialylation, and impaired platelet production mainly due to inhibition of thrombopoiesis, could be relevant mechanisms leading to thrombocytopenia in SLE. These findings could provide a rational basis for the choice of proper therapies to correct platelet counts in these patients.[Figure: see text].

Blood Count-derived Immunoinflammatory Markers in Thyroidassociated Ophthalmopathy

Purpose

To investigate the diagnostic and prognostic significance of the blood-count derived systemic immunoinflammatory parameters in patients with thyroid-associated ophthalmopathy (TAO).

Methods

In this retrospective case-control study, the blood-count parameters and neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio, and systemic immune-inflammatory index (SII), thyroid peroxidase antibody, and anti-thyroglobulin antibody were evaluated in 46 patients with TAO and 46 matched controls. The associations of the immunoinflammatory parameters with clinical outcomes were analyzed among TAO patients.

Results

Significant differences were found in NLR, PLR, SII, and lymphocyte count between the controls and the TAO group (p < 0.05 for all). In logistic regression analysis, these inflammatory parameters did not have any prognostic effect on the clinical outcomes of the TAO (p > 0.05 for all). The patients, who needed systemic treatment due to any ocular involvement of TAO during the follow-up period, had significantly lower platelet count (p = 0.001) and PLR (p = 0.02) at the time of initial diagnosis when compared to the no treatment-needed group of the TAO patients. The initial platelet count was significantly associated with the subsequent steroid need due to TAO during the follow-up period (β = −0.02, p = 0.03).

Conclusions

NLR, PLR, and SII may serve as potential inflammatory markers in the identification of the TAO, although they have no evident prognostic significance in TAO. However, the relatively lower platelet count at initial diagnosis may be associated with the need for systemic therapy during the follow-up in patients with TAO.

FcγRIIA expression accelerates nephritis and increases platelet activation in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune inflammatory disease characterized by deposits of immune complexes (ICs) in organs and tissues. The expression of FcγRIIA by human platelets, which is their unique receptor for immunoglobulin G antibodies, positions them to ideally respond to circulating ICs. Whereas chronic platelet activation and thrombosis are well-recognized features of human SLE, the exact mechanisms underlying platelet activation in SLE remain unknown. Here, we evaluated the involvement of FcγRIIA in the course of SLE and platelet activation. In patients with SLE, levels of ICs are associated with platelet activation. Because FcγRIIA is absent in mice, and murine platelets do not respond to ICs in any existing mouse model of SLE, we introduced the FcγRIIA (FCGR2A) transgene into the NZB/NZWF1 mouse model of SLE. In mice, FcγRIIA expression by bone marrow cells severely aggravated lupus nephritis and accelerated death. Lupus onset initiated major changes to the platelet transcriptome, both in FcγRIIA-expressing and nonexpressing mice, but enrichment for type I interferon response gene changes was specifically observed in the FcγRIIA mice. Moreover, circulating platelets were degranulated and were found to interact with neutrophils in FcγRIIA-expressing lupus mice. FcγRIIA expression in lupus mice also led to thrombosis in lungs and kidneys. The model recapitulates hallmarks of human SLE and can be used to identify contributions of different cellular lineages in the manifestations of SLE. The study further reveals a role for FcγRIIA in nephritis and in platelet activation in SLE.

Plasma Fibrinogen and Platelet Count Are Referable Tools for Diagnosing Periprosthetic Joint Infection: A Single-Center Retrospective Cohort Study

BACKGROUND

Although the MusculoSkeletal Infection Society has suggested a series of markers to diagnose periprosthetic joint infection (PJI), no single marker can accurately identify infection before revision hip or knee arthroplasty, and exploring promising markers to easily and reliably diagnose PJI is ongoing. The aim of this study was to evaluate the diagnostic value of plasma fibrinogen and platelet count for diagnosing PJI.

METHODS

We retrospectively included 439 patients who underwent revision arthroplasty from January 2008 to December 2018; 79 patients with coagulation-related comorbidities were evaluated separately. The remaining 360 patients constituted 153 PJI and 207 non-PJI patients. Receiver operating characteristic curves were used to evaluate the maximum sensitivity and specificity of the tested markers.

RESULTS

The receiver operating characteristic curves showed that the areas under the curve for plasma fibrinogen, platelet count, and serum C-reactive protein and erythrocyte sedimentation rate were 0.834, 0.746, 0.887, and 0.842, respectively. Based on Youden's index, the optimal predictive cutoffs for fibrinogen and platelet count were 3.57 g/L and 221 × 10⁹/L, respectively. The sensitivity and specificity, respectively, were 68.6% and 86.0% (fibrinogen) and 57.5% and 83.1% (platelet count) for diagnosing PJI. The sensitivity and specificity, respectively, were 76.7% and 72.2% (fibrinogen) and 48.8% and 63.9% (platelet count) for diagnosing PJI in patients with coagulation-related comorbidities.

CONCLUSION

Plasma fibrinogen performed well for diagnosing PJI before revision arthroplasty, and its value neared that of traditional inflammatory markers. Although the diagnostic value of the platelet count was inferior to traditional markers, its diagnostic value was fair for diagnosing PJI. Fibrinogen also may be useful for diagnosing PJI in patients with coagulation-related comorbidities.

In systemic lupus erythematosus anti-dsDNA antibodies can promote thrombosis through direct platelet activation

Systemic lupus erythematosus (SLE) is associated with a high risk of venous and arterial thrombosis, not necessarily associated with prothrombotic antiphospholipid antibodies (Abs). Alternatively, thrombosis may be due to an increased titer of anti-dsDNA Abs that presumably promote thrombosis via direct platelet activation. Here, we investigated effects of purified anti-dsDNA Abs from the blood of SLE patients, alone or in a complex with dsDNA, on isolated normal human platelets. We showed that anti-dsDNA Abs and anti-dsDNA Ab/dsDNA complexes induced strong platelet activation assessed by enhanced P-selectin expression and dramatic morphological and ultrastructural changes. Electron microscopy revealed a significantly higher percentage of platelets that lost their discoid shape, formed multiple filopodia and had a shrunken body when treated with anti-dsDNA Abs or anti-dsDNA Ab/dsDNA complexes compared with control samples. In addition, these platelets activated with anti-dsDNA Ab/dsDNA complexes typically contained a reduced number of secretory α-granules that grouped in the middle and often merged into a solid electron dense area. Many activated platelets released plasma membrane-derived microvesicles and/or fell apart into subcellular cytoplasmic fragments. Confocal microscopy revealed that platelets treated with anti-dsDNA Ab/dsDNA complex had a heterogeneous distribution of septin2 compared with the homogeneous distribution in control platelets. Structural perturbations were concomitant with mitochondrial depolarization and a decreased content of platelet ATP, indicating energetic exhaustion. Most of the biochemical and morphological changes in platelets induced by anti-dsDNA Abs and anti-dsDNA Ab/dsDNA complexes were prevented by pre-treatment with a monoclonal mAb against FcγRIIA. The aggregate of data indicates that anti-dsDNA Abs alone or in a complex with dsDNA strongly affect platelets via the FcγRIIA receptor. The immune activation of platelets with antinuclear Abs may comprise a prothrombotic mechanism underlying a high risk of thrombotic complications in patients with SLE.

Clinical aspects and risk factors of lupus nephritis: a retrospective study of 156 adult patients

Objective

To analyze the clinical manifestations, laboratory indexes, disease activity, and pathological types of lupus nephritis (LN) in adult patients.

Methods

We retrospectively analyzed the clinical manifestations, laboratory indexes, and pathological classifications of 156 adult patients first diagnosed with LN between July 2013 and November 2017. Patients were categorized according to the following criteria: active or inactive LN, LN with or without renal damage, and mild or severe LN.

Results

Immunoglobulin G and A levels, 24-hour proteinuria, and anti-dsDNA, anti-Sm, and anti-ribosomal P protein antibody positivity rates were all significantly increased in patients with active LN compared with inactive LN. Anti-dsDNA antibody positivity and 24-hour proteinuria were significantly increased, whereas hemoglobin, serum albumin, and C3 and C4 levels were significantly decreased in patients with LN and renal damage compared with those without renal damage. Anti-dsDNA and anti-Sm antibody positivity rates and 24-hour proteinuria were significantly increased, while hemoglobin, serum albumin, C3 and C4 levels, and estimated glomerular filtration rate were significantly decreased in patients with severe LN compared with patients with mild LN.

Conclusions

LN can display various clinical manifestations, laboratory indexes, levels of disease activity, and pathological types in adult patients.

The non-haemostatic role of platelets in systemic lupus erythematosus

Dysregulation of lymphocyte function, accumulation of autoantibodies and defective clearance of circulating immune complexes and apoptotic cells are hallmarks of systemic lupus erythematosus (SLE). Moreover, it is now evident that an intricate interplay between the adaptive and innate immune systems contributes to the pathogenesis of SLE, ultimately resulting in chronic inflammation and organ damage. Platelets circulate in the blood and are chiefly recognized for their role in the prevention of bleeding and promotion of haemostasis; however, accumulating evidence points to a role for platelets in both adaptive and innate immunity. Through a broad repertoire of receptors, platelets respond promptly to immune complexes, complement and damage-associated molecular patterns, and represent a major reservoir of immunomodulatory molecules in the circulation. Furthermore, evidence suggests that platelets are activated in patients with SLE, and that they could contribute to the circulatory autoantigenic load through the release of microparticles and mitochondrial antigens. Herein, we highlight how platelets contribute to the immune response and review evidence implicating platelets in the pathogenesis of SLE.

The Platelet-to-Lymphocyte Ratio as an Inflammatory Marker in Rheumatic Diseases

The platelet-to-lymphocyte ratio (PLR) has emerged as an informative marker revealing shifts in platelet and lymphocyte counts due to acute inflammatory and prothrombotic states. PLR has been extensively examined in neoplastic diseases accompanied by immune suppression and thrombosis, which can be predicted by combined blood cell counts and their ratios. Several large observational studies have demonstrated the value of shifts in PLR in evaluating the severity of systemic inflammation and predicting infections and other comorbidities, in inflammatory rheumatic diseases. The value of PLR as an inflammatory marker increases when its fluctuations are interpreted along with other complementary hematologic indices, particularly the neutrophil-to-lymphocyte ratio (NLR), which provides additional information about the disease activity, presence of neutrophilic inflammation, infectious complications, and severe organ damage in systemic lupus erythematosus. PLR and NLR have high predictive value in rheumatic diseases with predominantly neutrophilic inflammation (e.g., Behçet disease and familial Mediterranean fever). High PLR, along with elevated platelet count, is potentially useful in diagnosing some systemic vasculitides, particularly giant-cell arteritis. A few longitudinal studies on rheumatic diseases have demonstrated a decrease in PLR in response to anti-inflammatory therapies. The main limitations of PLR studies are preanalytical faults, inadequate standardization of laboratory measurements, and inappropriate subject selection. Nonetheless, accumulating evidence suggests that PLR can provide valuable information to clinicians who encounter multisystem manifestations of rheumatic diseases, which are reflected in shifts in platelet, lymphocyte, neutrophil, or monocyte counts. Interpretation of PLR combined with complementary hematologic indices is advisable to more accurately diagnose inflammatory rheumatic diseases and predict related comorbidities.

Systemic Lupus Erythematosus for Primary Care

Systemic lupus erythematosus is a chronic autoimmune condition with variable organ system involvement; manifestations can range from mild to potentially life threatening. Early diagnosis is important, as progression of disease can be halted. Diagnosis is made by review of signs and symptoms, imaging, and serology.

Retrospective analysis of the risk of hemorrhage associated with moderate and severe thrombocytopenia of 173 patients with systemic lupus erythematosus

The aim of the study was to observe the risk of hemorrhage from moderate and severe thrombocytopenia in systemic lupus erythematosus (SLE).A retrospective analysis was undertaken of cases admitted to Qilu Hospital, China. Blood platelet counts (BPCs) of ≤20 × 10/L represent severe thrombocytopenia, and a BPC of 21 to 50 × 10/L indicates moderate thrombocytopenia. A comparison was made from the perspective of severity with a view to determine the influence of thrombocytopenia on the risk of hemorrhage and the results.Moderate and severe thrombocytopenia occurred in 173 cases, accounting for 15.2% of the total hospitalized patients with SLE with a male to female ratio of 1:23.7. The average age of those patients was 34.8 ± 14.6 years. In the group of severe thrombocytopenia, patients without visceral involvement had a mean age of onset of 31.4 ± 14.2 years with a median of 28.0 years compared with 37.8 ± 14.8 years with a median of 38.5 years for patients with visceral involvement; this difference was statistically significant (P = .034). Seventy-one (76.3%) of 93 patients with severe thrombocytopenia and 20 (25.0%) of 80 patients with moderate thrombocytopenia developed hemorrhagic conditions of various grades, the difference between both were markedly statistically significant. Twenty-three patients with SLE died. Nine deaths were due to a hemorrhage caused by thrombocytopenia, while more were caused by infection.Severe thrombocytopenia is a significant adverse prognostic factor of SLE. SLE with the main manifestation of thrombocytopenia tends to make younger visceral organ owners suffer.

New Insights on Platelets and Platelet-Derived Microparticles in Systemic Lupus Erythematosus

PURPOSE OF REVIEW

Current knowledge on the role of platelets and platelet-derived microparticles (PMPs) on the immune system has been fast-growing. Systemic lupus erythematosus (SLE) is a systemic auto-immune disorder characterized by a loss of tolerance toward nuclear auto-antigens. Although recent studies allowed a better understanding of SLE pathogenesis, there is an urgent need for the development of new treatments and the identification of new biomarkers to assess the disease activity. We describe here the state-of-the-art knowledge linking platelets and PMPs to SLE.

RECENT FINDINGS

Platelet system activation is a key event in the pathogenesis of SLE. Circulating immune complexes, anti-phospholipid antibodies, and infectious agents such as virus are the main activators of platelets in SLE. Platelet activation can be monitored through different ways such as P-selectin expression, mean platelet volume, or circulating PMP levels, suggesting their potential use as biomarkers. Upon activation, platelets promote type I interferon production, NETosis, dendritic cell activation, and T and B lymphocyte activation, all essential events contributing to the development of SLE. Of interest, platelets also play a fundamental role in SLE organ disease such as the development of cardiovascular, thrombotic, and renal diseases. Finally, we review current knowledge on drugs targeting platelet activation and their potential impact on SLE pathogenesis. Platelets play a major role in SLE pathogenesis and organ disease and represent a great potential for novel biomarkers and drug development.

Systemic lupus erythematosus and systemic sclerosis: All roads lead to platelets

Systemic lupus erythematosus (SLE) and systemic sclerosis (SSc) are two phenotypically distincts inflammatory systemic diseases. However, SLE and SSc share pathogenic features such as interferon signature, loss of tolerance against self-nuclear antigens and increased tissue damage such as fibrosis. Recently, platelets have emerged as a major actor in immunity including auto-immune diseases. Both SLE and SSc are characterized by strong platelet system activation, which is likely to be both the witness and culprit in their pathogenesis. Platelet activation pathways are multiple and sometimes redundant. They include immune complexes, Toll-like receptors activation, antiphospholipid antibodies and ischemia-reperfusion associated with Raynaud phenomenon. Once activated, platelet promote immune dysregulation by priming interferon production by immune cells, providing CD40L supporting B lymphocyte functions and providing a source of autoantigens. Platelets are actively implicated in SLE and SSc end-organ damage such as cardiovascular and renal disease and in the promotion of tissue fibrosis. Finally, after understanding the main pathogenic implications of platelet activation in both diseases, we discuss potential therapeutics targeting platelets.