Platelet antibodies, activated platelets and serum leptin in childhood immune thrombocytopenic purpura

Role of Long non Coding RNAs, NEAT1 and Lnc-DC Expression in Pediatric Immune Thrombocytopenic Purpura

Background

Pediatric immune thrombocytopenic purpura (ITP) is an autoimmune disease; whose etiology is unknown. lncRNAs are regulators of numerous actions, which participate in the development of autoimmune diseases. We evaluated the expression ofNEAT1 and Lnc-RNA in dendritic cell (Lnc-DC) in pediatric ITP.

Methods

Sixty ITP patients and 60 healthy subjects were enrolled in the present study; Real-time PCR was performed to assess the expression levels of NEAT1 and Lnc-DC in sera of children with ITP as well as healthy children.

Results

Both lncRNAs, NEAT1 and Lnc-DC were significantly upregulated in ITP patients in comparison to controls (p <0.0001 and P= 0.001 respectively). Furthermore, significant upregulation of the expression levels of NEAT1 and Lnc-DC were observed in the non-chronic compared with chronic ITP patients. Also, there was significant negative correlation between each of NEAT1 and Lnc-DC and platelet counts before treatment (r= -0.38; P= 0.003 and r= -0.461; P< 0.0001, respectively).

Conclusions

serum lncRNAs, NEAT1 and Lnc-DC could be used as potential biomarkers in differentiating childhood ITP patients and healthy controls in addition to differentiating non-chronic from chronic ITP which may provide a theoretical basis for the mechanism and treatment of immune thrombocytopenia.

The Role of Leptin in Childhood Immune Thrombocytopenia (ITP): An Anti-Inflammatory Agent?

To investigate the effect of leptin in childhood ITP, we measured plasma leptin in 39 children with acute ITP, after treatment and in remission, and in 33 healthy age/BMI-matched controls. We also cultured ITP and control peripheral blood mononuclear cells (PBMCs) with recombinant leptin to assess its direct effect on pro/anti-inflammatory cytokine gene expression. A significant increase in leptin was observed in children with active disease compared to controls. A significant inverse correlation of leptin with platelet count was also observed in children with acute ITP. Leptin remained high after treatment with IVIg, whereas steroid treatment lowered leptin below control levels. In remission, leptin was in the control range. Cytokine gene expression was significantly increased in children with acute ITP compared with controls, with highest expression for IFN-γ and IL-10. IVIg/steroid treatment significantly decreased IFN-γ and IL-10 expression. In remission, IFN-γ and IL-10 expression remained low. Addition of leptin to PBMCs isolated from patients in remission resulted in a significant increase in IL-10 gene expression compared to controls. Further experiments with purified T-cells and monocytes identified monocytes as the source of leptin-induced IL-10. We suggest that leptin acts as an active anti-inflammatory agent in childhood ITP by promoting IL-10 secretion by monocytes.

CD4+ T cell phenotypes in the pathogenesis of immune thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune disorder characterized by low platelet counts due to enhanced platelet clearance and compromised production. Traditionally, ITP was regarded a B cell mediated disorder as anti-platelet antibodies are detected in most patients. The very nature of self-antigens, evident processes of isotype switching and the affinity maturation of anti-platelet antibodies indicate that B cells in order to mount anti-platelet immune response require assistance of auto-reactive CD4⁺ T cells. For a long time, ITP pathogenesis has been exclusively reviewed through the prism of the disturbed balance between Th1 and Th2 subsets of CD4⁺ T cells, however, more recently new subsets of these cells have been described including Th17, Th9, Th22, T follicular helper and regulatory T cells. In this paper, we review the current understanding of the role and immunological mechanisms by which CD4⁺ T cells contribute to the pathogenesis of ITP.

Platelet activation and neutrophil extracellular trap (NET) formation in immune thrombocytopenia: is there an association?

No biological predictors for the increased risk of thrombosis in patients with immune thrombocytopenia (ITP) have been identified. The aim of the study was to investigate platelet and neutrophil activation as well neutrophil extracellular trap (NET) formation in 63 ITP patients and 30 healthy volunteers. Platelet and neutrophil activation was assessed during steady state using flow cytometry analysis, and NETs were evaluated by quantitation of cell free DNA (cfDNA), and citrullinated histone-3-DNA (CitH3-DNA). Patient platelets and neutrophils showed increased CD62 and CD11b expression compared to controls (p = .038, and p = .022, respectively). In patients, platelet activation inversely correlated with platelet count and platelet size (p < .001), and positively correlated with neutrophil degranulation (p = .024). More NET formation, both CitH3-DNA (p = .025) and cfDNA(p < .001), were present in ITP patients compared to controls. CitH3-DNA inversely correlated with CD62 expression on platelets (p = .042), but higher levels of cfDNA were observed in individuals with classical cardiovascular risk factors for thrombosis, and in those with a previous history of thrombotic events. In this disease, the increased platelet activation and plasma NET levels seem to be separable processes that associate (either positively or inversely in the case of CitH3-DNA or platelet degranulation, respectively) to platelet mass.

Flow cytometric measurement of platelet-associated immunoglobulin in children with newly diagnosed Immune Thrombocytopenia

OBJECTIVE

To explore the clinical utility of measuring platelet-associated immunoglobulin (PAIG) at the time of diagnosis in children with immune thrombocytopenia (ITP).

METHODS

PAIG was measured by flow cytometry using fluorescent murine anti-IgG and anti-IgM. In a cohort of 88 children with ITP, the assay was performed within 15 days of diagnosis and before any treatment in 68 cases. We reviewed the results and examined the relation of isotype profile and degree of elevation to clinical manifestations and course of disease.

RESULTS

PAIG was elevated in 74%, with raised IgM being more frequent than IgG (63% vs. 44%, P = 0.04) and with isotype profile depending on symptom onset. Platelet counts at presentation were similar in all subgroups, but mucosal bleeding was less frequent in PAIG-negative patients compared to the positive groups (5.5% vs. 34%, P = 0.03). Duration of thrombocytopenia was similar in negative and positive cases, but during follow-up, significant bleeding events occurred less frequently in PAIG-negative patients (0% vs. 14%, P = 0.18).

CONCLUSION

Approximately one-quarter of children are PAIG-negative, and these children have milder bleeding tendency at diagnosis and lower morbidity during follow-up. Raised PAIG possibly may cause some degree of platelet dysfunction.