RESUMO
Transient myeloproliferative disorder (TMD) of the newborn and acute megakaryoblastic leukaemia (AMKL) in children with Down syndrome (DS) represent paradigmatic models of leukaemogenesis. Chromosome 21 gene dosage effects and truncating mutations of the X-chromosomal transcription factor GATA1 synergize to trigger TMD and AMKL in most patients. Here, we report the occurrence of TMD, which spontaneously remitted and later progressed to AMKL in a patient without DS but with a distinct dysmorphic syndrome. Genetic analysis of the leukaemic clone revealed somatic trisomy 21 and a truncating GATA1 mutation. The analysis of the patient's normal blood cell DNA on a genomic single nucleotide polymorphism (SNP) array revealed a de novo germ line 2·58 Mb 15q24 microdeletion including 41 known genes encompassing the tumour suppressor PML. Genomic context analysis of proteins encoded by genes that are included in the microdeletion, chromosome 21-encoded proteins and GATA1 suggests that the microdeletion may trigger leukaemogenesis by disturbing the balance of a hypothetical regulatory network of normal megakaryopoiesis involving PML, SUMO3 and GATA1. The 15q24 microdeletion may thus represent the first genetic hit to initiate leukaemogenesis and implicates PML and SUMO3 as novel components of the leukaemogenic network in TMD/AMKL.
Assuntos
Cromossomos Humanos Par 15/genética , Síndrome de Down/genética , Leucemia Megacarioblástica Aguda/genética , Transtornos Mieloproliferativos/genética , Proteínas Nucleares/genética , Deleção de Sequência , Fatores de Transcrição/genética , Proteínas Supressoras de Tumor/genética , Ubiquitinas/genética , Criança , Pré-Escolar , Síndrome de Down/patologia , Fator de Transcrição GATA1/genética , Humanos , Lactente , Leucemia Megacarioblástica Aguda/tratamento farmacológico , Leucemia Megacarioblástica Aguda/patologia , Masculino , Transtornos Mieloproliferativos/tratamento farmacológico , Transtornos Mieloproliferativos/patologia , Proteína da Leucemia PromielocíticaRESUMO
BACKGROUND: Endothelial progenitor cells (EPC) home to sites of vascular repair and therefore have potential implications in allogenic transplantation settings and in various vascular diseases. This study was performed to investigate the antigen-presenting capacity of peripheral blood mononuclear cells-derived EPC and their T-cell co-stimulatory capacity compared with human vascular endothelial cells (HUVEC) or monocytes. METHODS: EPC were isolated from peripheral blood mononuclear cells by adhesion to fibronectin. Antigen presentation and co-culture assays of EPC, HUVEC, monocytes, and dendritic cells with allogenic CD4 T cells were quantified by thymidine incorporation (cpm) and by quantitative reverse-transcriptase polymerase chain reaction (LightCycler) for cytokine production. RESULTS: Flow cytometric analyses revealed an expression of endothelial antigens (e.g., KDR) as well as monocytic antigens (e.g., CD14) in EPC. EPC effectively presented Mycobacterium tuberculosis antigen MTB 85B to DB3 hybridoma, a cell line specifically recognizing MTB 85B presented by means of human leukocyte antigen-DR3. In phytohemaglutinin-based CD4 T-cell co-stimulation assays, EPC-induced proliferation and cytokine production was comparable with monocytes and dendritic cells, whereas HUVEC-induced T-cell co-stimulation was markedly weaker. In contrast to HUVEC, EPC as well as monocytes activated naïve CD4/CD45RA T cells. Blocking experiments using CTLA-4-IgG fusion protein identified the CD28/CD80/86 system as a major co-stimulatory pathway for EPC-dependent T-cell activation. CONCLUSIONS: Although EPC exhibit endothelial-like surface markers, functional characteristics place these cells in a monocytic lineage. EPC also display antigen-presenting capacity similar to monocytes and much stronger than human vascular EC. Significant T-cell-activating potential will have to be expected from EPC when potentially used therapeutically, especially in allogenic transplant settings.
Assuntos
Células Dendríticas/imunologia , Células Endoteliais/imunologia , Endotélio Vascular/imunologia , Monócitos/imunologia , Células-Tronco/imunologia , Linfócitos T/imunologia , Animais , Especificidade de Anticorpos , Células Apresentadoras de Antígenos/imunologia , Antígenos/imunologia , Linfócitos T CD4-Positivos/imunologia , Técnicas de Cultura de Células , Citometria de Fluxo , Humanos , Hibridomas/imunologia , Ativação Linfocitária/imunologia , Camundongos , Veias UmbilicaisRESUMO
Effects of IL-10 on endothelium-dependent T cell activation have not been investigated in detail. We confirm expression of the IL-10 receptor and effective signaling via STAT-3 in human umbilical vein endothelial cells (HUVEC). In CD4 T cell cocultures with HUVEC, pretreatment of endothelial cells with IL-10 resulted in significant dose-dependent inhibition of CD4 T cell proliferation, which also occurred when IL-10 was removed after pretreatment before starting cocultures. Th1/Th2 polarization of proliferated T cells, endothelial nitric oxide (NO), or IL-12 production were unchanged. However, IL-10 stimulation resulted in up-regulation of SOCS-3, a negative regulator of cytokine secretion, and induction of the inhibitory surface molecules immunoglobulin-like transcript 3 and 4 (ILT3/ILT4) in EC, potentially involving glucocorticoid-induced leucine zipper (GILZ). Addition of blocking antibodies against ILT3/ILT4 to EC/T cell cocultures resulted in nearly complete reestablishment of T cell proliferation. In contrast, addition of soluble ILT3 or overexpression of ILT3 in cocultures significantly reduced T cell proliferation. No induction of foxp3+ regulatory T cells was seen. In conclusion, the T cell costimulatory potential of human EC is markedly suppressed by IL-10 due to up-regulation of ILT3/ILT4, obviously not involving generation of Treg. This identifies a novel action of IL-10 in EC and a potential therapeutical target for local immunomodulation.
