Association of Platelet Binding to Lymphocytes with B Cell Abnormalities and Clinical Manifestations in Systemic Lupus Erythematosus

Human B-cells can form Hetero-aggregates with Blood Platelets: A Novel Insight into Adaptive Immunity Regulation in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic autoimmune disease characterized by inflammation and neurodegeneration. Our original study analyzes the interactions between blood platelets and leukocytes in MS, focused on their potential role in modulating immune responses. We demonstrated, for the first time, a significant increase in leukocyte migration towards platelets, indicating their higher chemotactic capabilities in MS. This novel finding is supported by microscopic imaging of platelet-leukocyte hetero-aggregates (PLAs). Our study included platelet activation status and platelet-lymphocyte cross-talk analysis distinguishing lymphocytic subpopulation in patients with relapsing-remitting (RRMS) and secondary progressive MS (SPMS) compared to healthy controls (HC). Flow cytometry method revealed an elevated expression of platelet activation typical markers i.e. PAC-1 and CD62P in both phenotypes of MS, especially in RRMS, and higher GPVI level in SPMS. Detailed immunophenotyping and confocal imaging showed an increased pool of platelet-lymphocyte aggregates (PLAs-Ly), particularly involving B-cells over T-cells across both MS phenotypes. The study also explored the involvement of the CD40-CD40L pathway, discovering significant correlations between platelet CD40L expression and lymphocytic antigen CD40, especially on B-cells in SPMS. This novel finding may indicate the special significance of platelet-B-cell cross-talk in progressive disease phenotype. Our research identified potential platelet-leukocyte interaction pathways that may influence the lymphocyte-mediated immune response in MS, highlighting the unexplored formation of platelet-B cell hetero-aggregates (PLAs-LyB).

Immune thrombocytopenia in patients with systemic lupus erythematosus

Immune thrombocytopenia (ITP) is a common hematological manifestation of systemic lupus erythematosus (SLE). The diversity of its clinical features and treatment responses may reveal the complex pathophysiological mechanisms of the disease. To enhance the therapeutic response rate and improve the prognosis for SLE patients with concurrent ITP, while reducing adverse events during the treatment process, it is crucial to accurately identify and apply clinical parameters to predict patients' responses to treatment. In addition to conventional therapeutic approaches such as glucocorticoids, immunosuppressants, and intravenous immunoglobulin (IVIG), a range of emerging therapies are gradually becoming the focus of research. These innovative therapeutic strategies include thrombopoietin receptor agonists (TPO-RAs), targeted therapies against B-cells, and plasma cell-targeted treatments. With a deepening understanding of the role of platelets in immune and inflammatory responses, novel platelet-targeted therapeutic agents in the field of SLE-ITP treatment may demonstrate significant potential. Despite this, to ensure the clinical efficacy and safety of these therapeutic approaches, we must rely on rigorously designed randomized controlled trials (RCTs) for further validation. This article provides a systematic review of the pathogenesis of systemic lupus erythematosus (SLE) complicated by immune thrombocytopenia (ITP) and conducts a comprehensive overview of current treatment strategies. The article also provides an in-depth exploration of the key biomarkers that may influence the therapeutic response in SLE-ITP patients. This comprehensive analysis aims to elucidate the factors that potentially affect the efficacy of treatments and contribute to a more personalized approach to patient care.

Platelet signaling in immune landscape: comprehensive mechanism and clinical therapy

Platelets are essential for blood clotting and maintaining normal hemostasis. In pathological conditions, platelets are increasingly recognized as crucial regulatory factors in various immune-mediated inflammatory diseases. Resting platelets are induced by various factors such as immune complexes through Fc receptors, platelet-targeting autoantibodies and other platelet-activating stimuli. Platelet activation in immunological processes involves the release of immune activation stimuli, antigen presentation and interaction with immune cells. Platelets participate in both the innate immune system (neutrophils, monocytes/macrophages, dendritic cells (DCs) and Natural Killer (NK) cells and the adaptive immune system (T and B cells). Clinical therapeutic strategies include targeting platelet activation, platelet-immune cell interaction and platelet-endothelial cell interaction, which display positive development prospects. Understanding the mechanisms of platelets in immunity is important, and developing targeted modulations of these mechanisms will pave the way for promising therapeutic strategies.

Platelet's plea to Immunologists: Please do not forget me

Platelets are non-nucleated mammalian cells originating from the cytoplasmic expulsion of the megakaryocytes. Megakaryocytes develop during hematopoiesis through megakaryopoiesis, whereas platelets develop from megakaryocytes through thrombopoiesis. Since their first discovery, platelets have been studied as critical cells controlling hemostasis or blood coagulation. However, coagulation and innate immune response are evolutionarily linked processes. Therefore, it has become critical to investigate the immunological functions of platelets to maintain immune homeostasis. Advances in immunology and platelet biology research have explored different critical roles of platelets, including phagocytosis, release of different immune mediators, and controlling functions of different immune cells by direct interaction and immune mediators. The current article discusses platelet's development and their critical role as innate immune cells, which express different pattern recognition receptors (PRRs), recognizing different pathogen or microbe-associated molecular patterns (PAMPs or MAMPs) and death/damage-associated molecular patterns (DAMPs) and their direct interactions with innate and adaptive immune cells to maintain immune homeostasis.

Diagnostic value of contrast-enhanced ultrasound combined with serum procalcitonin in tuberculous lymph nodes and metastatic lymph nodes

OBJECTIVE

To investigate the value of Contrast-Enhanced Ultrasound (CEUS) combined with Procalcitonin (PCT) in differentiating Tuberculous Lymph Nodes (TLN) from Metastatic Lymph Nodes (MLN).

METHODS

This prospective cohort study included 207 consecutive patients diagnosed with CTL. All patients underwent routine ultrasound and CEUS prior to pathology or laboratory confirmation. Serum indicators were measured by Enzyme-Linked Immunosorbent Assay (ELISA). Predictive modeling was performed by multifactorial logistic regression. Evaluate the diagnostic and calibration performance of the predictive model by drawing Receiver Operating Characteristic (ROC) curves and calibration curves, and using Area Under the Curve (AUC) and Hosmer-Lemeshow (H-L) tests.

RESULTS

The diagnosis of MLN was confirmed pathologically or laboratory in 102 of 207 patients (49.27 %), and 50.8 % were confirmed to be TLN. According to imaging findings of CEUS, TLN was more commonly associated with enhanced concentric performance in the arterial phase (67.65 % vs. 40.95 %) and heterogeneous enhancement pattern in lymph nodes (70.59 % vs. 52.38 %). Peak Intensity (PI) of lesions was higher in patients with MLN. Increased age-enhanced concentric performance in the arterial phase, increased PI, and serum PCT greater than 5.39 ng/mL were independent risk factors for MLN. The prediction model of serum PCT combined with CEUS had a higher diagnostic value for MLN. The H-L test indicated a satisfactory model fit (all p > 0.05), and the calibration curve closely approximates the ideal diagonal.

CONCLUSION

CEUS combined with serum PCT has better clinical application value in the differential diagnosis of TLN and MLN.

The role of platelets and megakaryocytes in sepsis and ARDS

Since the global COVID-19 pandemic, there has been a renewed focus on lung injury during infection. Systemic inflammatory responses such as acute respiratory distress syndrome (ARDS) and sepsis are a leading cause of morbidity and mortality for both adults and children. Improvements in clinical care have improved outcomes but mortality remains ∼40% and significant morbidity persists for those patients with severe disease. Mechanistic studies of the underlying biological processes remain essential to identifying therapeutic targets. Furthermore, methods for identifying the underlying drivers of organ failure are key to treating and preventing tissue injury. In this review, we discuss the contribution of megakaryocytes (MKs) and platelets to the pathogenesis of systemic inflammatory syndromes. We explore the role of MKs and the new identification of extramedullary MKs during sepsis. We describe the alterations in the platelet transcriptome during sepsis. Lastly, we explore platelet function as defined by aggregation, activation and the formation of heterotypic aggregates. Much more work is necessary to explore the contribution of platelets to these heterogenous syndromes, but the foundation of platelets as key contributors to inflammation has been laid.

Modulating Immune Responses: The Double-Edged Sword of Platelet CD40L

The CD40-CD40L receptor ligand pair plays a fundamental role in the modulation of the innate as well as the adaptive immune response, regulating monocyte, T and B cell activation, and antibody isotype switching. Although the expression and function of the CD40-CD40L dyad is mainly attributed to the classical immune cells, the majority of CD40L is expressed by activated platelets, either in a membrane-bound form or shed as soluble molecules in the circulation. Platelet-derived CD40L is involved in the communication with different immune cell subpopulations and regulates their functions effectively. Thus, platelet CD40L contributes to the containment and clearance of bacterial and viral infections, and additionally guides leukocytes to sites of infection. However, platelet CD40L promotes inflammatory cellular responses also in a pathophysiological context. For example, in HIV infections, platelet CD40L is supportive of neuronal inflammation, damage, and finally HIV-related dementia. In sepsis, platelet CD40L can induce extensive endothelial and epithelial damage resulting in barrier dysfunction of the gut, whereby the translocation of microbiota into the circulation further aggravates the uncontrolled systemic inflammation. Nevertheless, a distinct platelet subpopulation expressing CD40L under septic conditions can attenuate systemic inflammation and reduce mortality in mice. This review focuses on recent findings in the field of platelet CD40L biology and its physiological and pathophysiological implications, and thereby highlights platelets as vital immune cells that are essential for a proper immune surveillance. In this context, platelet CD40L proves to be an interesting target for various inflammatory diseases. However, either an agonism or a blockade of CD40L needs to be well balanced since both the approaches can cause severe adverse events, ranging from hyperinflammation to immune deficiency. Thus, an interference in CD40L activities should be likely done in a context-dependent and timely restricted manner.

Interplay of leucocyte-platelet complexes and clinical response to eltrombopag in immune thrombocytopenia patients

Eltrombopag (ELT) is a thrombopoietin-receptor agonist that stimulates platelet (PLT) production in patients with primary immune thrombocytopenia (ITP). One potential mechanism of ELT is modulating the inflammatory response by increasing PLTs binding to leucocytes. This study examined the effect of ELT on leucocyte-PLTs complexes in 38 ITP patients. Patients, predominantly females with a mean age of 59 years, underwent treatments like corticosteroids, intravenous immunoglobulin and splenectomy. Compared to healthy donors, ITP patients exhibited lower percentages of lymphocyte with bound PLTs, but similar monocyte- or neutrophil with bound PLTs. ELT treatment increased PLTs counts and all types of leucocyte with bound PLTs. Network analysis showed dynamic changes in leucocyte with bound PLTs relationships due to ELT. Machine learning indicated that higher percentages of monocytes with bound PLTs were linked to a better clinical response to ELT. A possible mechanism was an increased IL-10 production in monocytes with bound PLTs from responder patients. This study provides insights into the immunological changes in ITP patients undergoing ELT and suggests potential predictive biomarkers for treatment response and disease monitoring.

B Cell Lymphocytes as a Potential Source of Breast Carcinoma Marker Candidates

Despite advances in the genomic classification of breast cancer, current clinical tests and treatment decisions are commonly based on protein-level information. Nowadays breast cancer clinical treatment selection is based on the immunohistochemical (IHC) determination of four protein biomarkers: Estrogen Receptor 1 (ESR1), Progesterone Receptor (PGR), Human Epidermal Growth Factor Receptor 2 (HER2), and proliferation marker Ki-67. The prognostic correlation of tumor-infiltrating T cells has been widely studied in breast cancer, but tumor-infiltrating B cells have not received so much attention. We aimed to find a correlation between immunohistochemical results and a proteomic approach in measuring the expression of proteins isolated from B-cell lymphocytes in peripheral blood samples. Shotgun proteomic analysis was chosen for its key advantage over other proteomic methods, which is its comprehensive and untargeted approach to analyzing proteins. This approach facilitates better characterization of disease-associated changes at the protein level. We identified 18 proteins in B cell lymphocytes with a significant fold change of more than 2, which have promising potential to serve as breast cancer biomarkers in the future.

Platelets and inter-cellular communication in immune responses: Dialogue with both professional and non-professional immune cells

Platelets, derived from bone marrow megakaryocytes, are essential for vascular integrity and play multifaceted roles in both physiological and pathological processes within the vasculature. Despite their small size and absence of a nucleus, platelets are increasingly recognized for their diverse immune functions. Recent research highlights their pivotal role in interactions with various immune cells, including professional cells like macrophages, dendritic cells, natural killer cells, T cells, and B cells, influencing host immune responses. Platelets also engage with non-professional immune cells, contributing to immune responses and structural maintenance, particularly in conditions like inflammation and atherosclerosis. This review underscores the emerging significance of platelets as potent immune cells, elucidating their interactions with the immune system. We explore the mechanisms of platelet activation, leading to diverse functions, such as aggregation, immunity, activation of other immune cells, and pathogen clearance. Platelets have become the predominant immune cells in circulation, involved in chronic inflammation, responses to infections, and autoimmune disorders. Their immunological attributes, including bioactive granule molecules and immune receptors, contribute to their role in immune responses. Unlike professional antigen-presenting cells, platelets process and present antigens through an MHC-I-dependent pathway, initiating T-cell immune responses. This review illuminates the unique features of platelets and their central role in modulating host immune responses in health and disease.

Platelets are a major player and represent a therapeutic opportunity in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by immune dysregulation and organ injury with a premature mortality due to cardiovascular diseases. Platelets, that are primarily known for their role in hemostasis, have been shown to play an active role in the pathogenesis and in the progression of immune-mediated inflammatory diseases. Here we summarize the evidence of their roles in SLE pathogenesis which supports the development of targeted treatments. Platelets and their precursors, the megakaryocytes, are intrinsically different in SLE patients compared with healthy controls. Different triggers related to innate and adaptive immunity activate platelets which release extracellular vesicles, soluble factors and interact with immune cells, thereby perpetuating inflammation. Platelets are involved in organ damage in SLE, especially in lupus nephritis and participate in the heightened cardiovascular mortality. They also play a clear role in antiphospholipid syndrome which can be associated with both thrombocytopenia and thrombosis. To tackle platelet activation and their interactions with immune cells now constitute promising therapeutic strategies in SLE.

The role of platelets in immune-mediated inflammatory diseases

Immune-mediated inflammatory diseases (IMIDs) are characterized by excessive and uncontrolled inflammation and thrombosis, both of which are responsible for organ damage, morbidity and death. Platelets have long been known for their role in primary haemostasis, but they are now also considered to be components of the immune system and to have a central role in the pathogenesis of IMIDs. In patients with IMIDs, platelets are activated by disease-specific factors, and their activation often reflects disease activity. Here we summarize the evidence showing that activated platelets have an active role in the pathogenesis and the progression of IMIDs. Activated platelets produce soluble factors and directly interact with immune cells, thereby promoting an inflammatory phenotype. Furthermore, platelets participate in tissue injury and promote abnormal tissue healing, leading to fibrosis. Targeting platelet activation and targeting the interaction of platelets with the immune system are novel and promising therapeutic strategies in IMIDs.

Phenotypic and Functional Consequences of PLT Binding to Monocytes and Its Association with Clinical Features in SLE

Platelets (PLTs) can modulate the immune system through the release of soluble mediators or through interaction with immune cells. Monocytes are the main immune cells that bind with PLTs, and this interaction is increased in several inflammatory and autoimmune conditions, including systemic lupus erythematosus (SLE). Our aim was to characterize the phenotypic and functional consequences of PLT binding to monocytes in healthy donors (HD) and in SLE and to relate it to the pathogenesis of SLE. We analyzed the phenotypic and functional features of monocytes with non-activated and activated bound PLTs by flow cytometry. We observed that monocytes with bound PLTs and especially those with activated PLTs have an up-regulated HLA-DR, CD86, CD54, CD16 and CD64 expression. Monocytes with bound PLTs also have an increased capacity for phagocytosis, though not for efferocytosis. In addition, monocytes with bound PLTs have increased IL-10, but not TNF-α, secretion. The altered phenotypic and functional features are comparable in SLE and HD monocytes and in bound PLTs. However, the percentages of monocytes with bound PLTs are significantly higher in SLE patients and are associated with undetectable levels of anti-dsDNA antibodies and hematuria, and with normal C3 and albumin/creatinine levels. Our results suggest that PLTs have a modulatory influence on monocytes and that this effect may be highlighted by an increased binding of PLTs to monocytes in autoimmune conditions.

The Dual Role of Platelets in the Cardiovascular Risk of Chronic Inflammation

Patients with chronic inflammatory diseases often exhibit cardiovascular risk. This risk is associated with the systemic inflammation that persists in these patients, causing a sustained endothelial activation. Different mechanisms have been considered responsible for this systemic inflammation, among which activated platelets have been regarded as a major player. However, in recent years, the role of platelets has become controversial. Not only can this subcellular component release pro- and anti-inflammatory mediators, but it can also bind to different subsets of circulating lymphocytes, monocytes and neutrophils modulating their function in either direction. How platelets exert this dual role is not yet fully understood.

Moving toward targeting the right phenotype with the right platelet-rich plasma (PRP) formulation for knee osteoarthritis

Intra-articular injections of platelet-rich plasma (PRP) and other novel blood-derived products developed specifically for osteoarthritis (OA) can provide pain relief and potential benefits in disease progression. Meta-analyses show the clinical superiority of PRP compared with other intra-articular injections, but results are modest and the effect sizes are small. PRP injections in knee OA are performed indiscriminately, but the clinical response varies enormously between patients because of an array of mixed OA phenotypes. Subgroup analyses are scarce; some studies stratify patients according to radiographic severity and found better results in early OA, without consensus for more advanced stages of the condition. Parallel identification of soluble and imaging biomarkers is essential to personalise and leverage PRP therapies. The inflammatory phenotype is most interesting from the PRP perspective because PRPs modulate inflammation by releasing a large pool of chemokines and cytokines, which interact with synovial fibroblasts and macrophages; in addition, they can modulate the innate immune response. No soluble biomarkers have been discovered that have implications for OA research and PRP interventions. Clinical examination of patients based on their inflammatory phenotype and imaging identification of pain sources and structural alterations could help discern who will respond to PRP. Synovial inflammation and bone marrow lesions are sources of pain, and intra-articular injections of PRP combined with subchondral bone injection can enhance clinical outcomes. Further refining ultrasound phenotypes may aid in personalising PRP therapies. Intra-articular delivery combined with injections in altered ligamentous structures, medial and coronal ligaments or premeniscal pes anserinus showed positive clinical outcomes. Although the evidence supporting these approaches are weak, they merit further consideration to refine PRP protocols and target the right OA phenotypes.

The Immune Nature of Platelets Revisited

Platelets are the primary cellular mediators of hemostasis and this function firmly acquaints them with a variety of inflammatory processes. For example, platelets can act as circulating sentinels by expressing Toll-like receptors (TLR) that bind pathogens and this allows platelets to effectively kill them or present them to cells of the immune system. Furthermore, activated platelets secrete and express many pro- and anti-inflammatory molecules that attract and capture circulating leukocytes and direct them to inflamed tissues. In addition, platelets can directly influence adaptive immune responses via secretion of, for example, CD40 and CD40L molecules. Platelets are also the source of most of the microvesicles in the circulation and these miniscule elements further enhance the platelet’s ability to communicate with the immune system. More recently, it has been demonstrated that platelets and their parent cells, the megakaryocytes (MK), can also uptake, process and present both foreign and self-antigens to CD8+ T-cells conferring on them the ability to directly alter adaptive immune responses. This review will highlight several of the non-hemostatic attributes of platelets that clearly and rightfully place them as integral players in immune reactions.

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Platelets can act as circulating sentinels by expressing pathogen-associated molecular pattern receptors that bind pathogens and induce their killing and elimination.

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Activated platelets secrete and express a multitude of pro- and anti-inflammatory molecules that attract and capture circulating leukocytes and direct them to inflamed tissues.

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Platelets express and secrete many critical immunoregulatory molecules that significantly affect both innate and adaptive immune responses.

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Platelets are the primary source of microparticles in the circulation and these augment the platelet’s ability to communicate with the immune system.

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Platelets and megakaryocytes can act as antigen presenting cells and present both foreign- and self-peptides to T-cells.