Paola Saracco

Wiskott-Aldrich Syndrome Protein Regulates Lipid Raft Dynamics during Immunological Synapse Formation

Immunological synapse assembly relies on the clustering of lipid rafts and is required for optimal T cell activation. We demonstrate that the Wiskott-Aldrich syndrome protein (WASP) is recruited to lipid rafts immediately after TCR and CD28 triggering and is required for the movements of lipid rafts. T cells from Wiskott-Aldrich syndrome (WAS) patients, lacking WASP, proliferate poorly after TCR/CD28 activation and have impaired capacities to cluster the lipid raft marker GM1 and to upregulate GM1 cell surface expression. T cell proliferation and lipid raft clustering are restored by retroviral transfer of the WASP gene. These results demonstrate that WASP plays a central role in the movements of lipid rafts and identify a potential mechanism underlying the T cell defect affecting WAS patients.

Defective Th1 cytokine gene transcription in CD4+ and CD8+ T cells from Wiskott-Aldrich syndrome patients.

Wiskott-Aldrich syndrome (WAS) protein (WASP) plays a key role in TCR-mediated activation and immunological synapse formation. However, the effects of WASP deficiency on effector functions of human CD4+ and CD8+ T cells remain to be determined. In this study, we report that TCR/CD28-driven proliferation and secretion of IL-2, IFN-γ, and TNF-α are strongly reduced in CD8+ T cells from WAS patients, compared with healthy donor CD8+ T cells. Furthermore, WAS CD4+ T cells secrete low levels of IL-2 and fail to produce IFN-γ and TNF-α, while the production of IL-4, IL-5, and IL-10 is only minimally affected. Defective IL-2 and IFN-γ production persists after culture of naive WAS CD4+ T cells in Th1-polarizing conditions. The defect in Th1 cytokine production by WAS CD4+ and CD8+ T cells is also present at the transcriptional level, as shown by reduced IL-2 and IFN-γ mRNA transcripts after TCR/CD28 triggering. The reduced transcription of Th1 cytokine genes in WAS CD4+ T cells is associated with a defective induction of T-bet mRNA and a reduction in the early nuclear recruitment of NFAT-1, while the defective activation of WAS CD8+ T cells correlates with reduced nuclear recruitment of both NFAT-1 and NFAT-2. Together, our data indicate that WASP regulates the transcriptional activation of T cells and is required specifically for Th1 cytokine production.

Cyclosporin A response and dependence in children with acquired aplastic anaemia: a multicentre retrospective study with long-term observation follow-up.

Immunosuppressive therapy (IST) with antithymocyte globulin and cyclosporin A (CyA) is the standard treatment for children with acquired aplastic anaemia (AAA) lacking a matched donor. Survival rates of more than 80% at 5 years are achieved, but the response is drug‐dependent in 15–25% of cases. This study, of 42 consecutive children with AAA treated with IST, assessed the incidence of CyA‐dependence, CyA and granulocyte colony‐stimulating factor (G‐CSF) tapering schedules and the impact of drug accumulation on progression to myelodysplasia/acute myeloid leukaemia (MDS/AML). Overall survival was 83% at 10 years. CyA‐dependence without a predictive marker was observed in 18% of responders. Probability of discontinuing CyA was 60·5% at 10 years; a slow CyA tapering schedule was performed in 84% of patients; the cumulative incidence of relapse was 16% at 10 years. Relapse risk was significantly associated with rapid CyA discontinuation: 60% compared to 7·6% in the slow tapering group (P = 0·001). Cumulative incidence of MDS/AML was 8% at 10 years, with a significant correlation with both G‐CSF cumulative dose and second IST. This long‐term follow‐up of children with AAA shows that IST with a slow CyA tapering course is an effective treatment with a low‐relapse rate in these cases.

Endothelial activation, inflammation and premature atherosclerosis in children with familial dyslipidemia.

OBJECTIVES Prospective studies demonstrated an increased cardiovascular risk in subjects with high levels of either the endothelial-platelet activation marker P-selectin or high-sensitivity C-reactive protein (hs-CRP). Both children with heterozygous familial hypercholesterolemia (FH) and those with familial combined hyperlipidemia (FCHL) are prone to premature atherosclerosis. Our objective was to investigate in children with either FH or FCHL whether P-selectin and hs-CRP contribute to carotid intima-media thickness (IMT), along with increased plasma lipid levels. METHODS Carotid IMT, serum lipids and soluble P-selectin and hs-CRP levels were measured in 88 children (mean age 10.5+/-4.3 years) including 44 dyslipidemic children (25 with FH and 19 with FCHL) and 44 non-dyslipidemic controls. RESULTS Carotid IMT was significantly higher among dyslipidemic than in control children (0.46+/-0.06mm vs 0.43+/-0.06mm, p=0.003) and serum P-selectin levels as well [129(50-254)ng/mL vs 50(24.5-130)ng/mL, p<0.001]. FH but not FCHL children had higher hs-CRP levels than controls [0.7(0.01-6.9)mg/L vs 0.3(0.1-1.2)mg/L, p=0.006]. In the entire sample of dyslipidemic children, carotid IMT was positively associated with soluble P-selectin levels (rho=0.30, p=0.049), but not with hs-CRP. The association between P-selectin and carotid IMT was independent from confounders, including plasma lipid levels. CONCLUSION Endothelial-platelet activation, more than low-grade systemic inflammation, correlates with premature atherosclerosis among children with familial dyslipidemia, this association being independent from plasma lipid levels.

Adrenal axis function after high-dose steroid therapy for childhood acute lymphoblastic leukemia

Background A 4‐week course of high‐dose glucocorticoids may cause prolonged adrenal suppression even after a 9‐day tapering phase. In this study, adrenal function and signs and symptoms of adrenal insufficiency were prospectively assessed in children with acute lymphoblastic leukemia (ALL) after induction treatment including high‐dose prednisone (PDN) or dexamethasone (DXM). Procedures Sixty‐four children with ALL, treated according to the AIEOP ALL 2000 Study protocol, underwent low dose ACTH (LD‐ACTH) stimulation 24 hr after the last tapered steroid dose. In those with impaired cortisol response, additional LD ACTH tests were performed every 1–2 weeks until cortisol levels normalized. Signs and symptoms of adrenal insufficiency were recorded during the observation period. Results All patients had normal basal cortisol values at diagnosis. Twenty‐four hours after last glucocorticoid dose, morning cortisol was reduced in 40/64 (62.5%) patients. LD‐ACTH testing showed adrenal suppression in 52/64 (81.5%) patients. At the following ACTH test 7–14 days later, morning cortisol values were reduced in 8/52 (15.4%) patients and response to the test was impaired in 12/52 (23%). Adrenal function completely recovered in all patients within 10 weeks. No difference was found between patients treated with PDN or DXM. Almost 35% of children with impaired cortisol values at the first test developed signs or symptoms of adrenal insufficiency. One child developed a severe adrenal crisis during adrenal suppression. Conclusions High‐dose glucocorticoid therapy in ALL children may cause prolonged adrenal suppression and related clinical symptoms. Laboratory monitoring of cortisol levels and steroid coverage during stress episodes may be indicated. Pediatr Blood Cancer 2008;50:537–541.

Prospective study of hemostatic alterations in children with acute lymphoblastic leukemia

In a group of newly diagnosed acute lymphocytic leukemia (ALL) children we evaluated a number of hemostatic and inflammatory markers at diagnosis and at different time points during chemotherapy for the remission induction to identify alterations in the plasma levels of prothrombotic markers before and during the course of chemotherapy. The following plasma markers were evaluated: thrombin‐antithrombin complex (TAT), D‐Dimer, plasminogen activator inhibitor 1 (PAI‐1), antithrombin, fibrinogen, von Willebrand factor (VWF) antigen and high molecular weight VWF (HMW‐VWF) multimers, P‐selectin, tumor necrosis factor alpha (TNF‐α), and interleukin 6 (IL‐6). Plasma samples were collected at the following time points: at T0 (baseline) and T1 (+24 days of therapy), T2 (+36 days therapy), and T3 (+64 days therapy). The results show that, at diagnosis, ALL children presented with laboratory signs of increased thrombin generation and fibrin formation (i.e. high TAT and D‐dimer levels), fibrinolysis inhibition (i.e. high PAI‐1 level), endothelial activation (i.e., high HMW‐VWF and soluble P‐selectin levels) and inflammation (i.e. high TNF‐alpha and IL‐6 levels). After starting induction therapy, the thrombin generation markers and inflammatory cytokines significantly decreased. To the opposite, PAI‐1 and P‐selectin significantly increased, suggesting an insult by chemotherapy on the vascular endothelium. These effects were more evident during steroid administration. Symptomatic venous thromboembolism (VTE) episodes developed in two cases during induction therapy, which did not allow the evaluation of the predictive value for VTE of laboratory markers. Am. J. Hematol., 2010.

Hematological Studies in Children with Down Syndrome

Previous studies have reported erythrocyte macrocytosis in adults and children with Down syndrome (DS), the significance of which remains unclear. We compared hematological parameters of 50 DS children aged 2 to 15 years, divided into three age groups, with those of 68 aged-matched healthy children. Patients with DS had a significantly increased mean corpuscular volume (MCV) and hemoglobin in all groups when compared with the controls. Erythrocyte creatine content, hexokinase (Hk) activity, erythrocyte and serum folates, vitamin B12, haptoglobin, serum iron, and ferritin were tested. All of these parameters were not significantly different from those of the control group. We conclude that macrocytosis may not be an expression of reduced red cell survival but rather of an altered folate remethylation pathway, secondary to enhanced cystathionine beta-synthase (CBS) activity, the gene for which is present on chromosome 21.

Cell adhesion molecule expression in cord blood CD34+ cells.

Self‐renewal, proliferation, differentiation, homing, and mobilization of hematopoietic progenitor cells (HPCs) are regulated by a complex mechanism that involves the bone marrow (BM) microenvironment. Cell adhesion molecules (CAMs) expressed on HPCs and on endothelial and stromal cells play a pivotal role in this process. In this study, we have used three‐color cytofluorometric analysis to compare CAM expression in the subsets of cord blood (CB) and BM HPCs and examined the effect of a short exposure to various cytokines on L‐selectin expression. The study was carried out on unseparated samples to avoid any possible bias from positive CD34 selection. CAMs were highly expressed in both CB and BM CD34+CD38+ cells. In this population, L‐selectin, H‐CAM, and LFA‐1 were significantly more expressed in BM than in CB.

Management and investigation of neonatal thromboembolic events: Genetic and acquired risk factors

Newborns comprise the largest group of children developing thromoboembolic events (TE(S)), due to the peculiarities of their developmental hemostatic system. Moreover, in the sick newborn, especially preterm, numerous acquired perinatal and iatrogenic conditions might result in a disturbance between coagulation and fibrinolysis, leading to thrombus formation. Nevertheless, the contribution of acquired prothrombotic disorders in the pathogenesis of thromboembolic disease in newborns remains poorly defined. Few data are currently available regarding the influence of maternal or fetal genes on thrombotic risk in the fetus and neonate. Ongoing National and International registries are partially answering these questions. The purpose of this review is to evaluate the current knowledge about the role of inherited, acquired perinatal and maternal prothrombotic risk factors in neonatal cerebral nervous system (CNS) thrombotic events and non-CNS thrombotic events.

Risk factors of central venous lines-related thrombosis in children with acute lymphoblastic leukemia during induction therapy: a prospective study

Risk factors of central venous lines-related thrombosis in children with acute lymphoblastic leukemia during induction therapy: a prospective study