Background: mutations in SH2D1A/DSHP/SAP gene are responsible for the onset of X-linked lymphoproliferative disease type 1 (XLP1) that have increased risk for B-ceil lymphoma development. In XLP1 patients SAP deficient NK, NKT and CD8+ cytotoxic T cells are inefficient in eliminating EBV-infected proliferating B cells that may partially contribute to the lymphoma development. However, little is known about impairment of B cell characteristics in XLPI. Aim: to analyze the cell surface phenotype and functional characteristics of EBV-transformed B-lymphoblastoid cell lines from XLPI patients (XLP B-LCLs) in comparison with conventional B-lymphoblastoid cell lines (B-LCLs). Studies were performed on SAP-negative B-LCLs T5-1, 6.16, RPMI1788; SAP-positive B-LCLMP-1 and XLP B-LCLs IARC 739, XLP-D, XLP-8005. Cell surface immunophenotyping was performed using flow cytometry analysis. The level of apoptotic cells (Annexin V-binding), cell viability (MTT assay), and cell proliferation (trypan blue exclusion test) were evaluated in response to ligation of CD40, CD95, CD150 and IgM cell surface receptors. A cell surface phenotype and functional features that distinguish XLP B-LCLs from conventional B-LCLs were revealed. XLP B-LCLs showed the upregulated level of CD20, CD38 and CD86 cell surface expression and down-regulation of CD40, CD80 and CD150 expression. The major functional differences of XLP B-LCLs from conventional B-LCLs concern the modulation of CD95 apoptosis via CD40 and CD150 receptors and unresponsiveness to proliferative signals triggered by CD40 or colligation of BCR with CD150. Conclusion: the data suggest that the B-LCL from XLPI patients have an intrinsic defect that affects cell activation, apoptosis, and proliferation.Background: X-linked lymphoproHfcrativc disease type 1 (XLP1) belongs to genetically determined primary immunodericiency syndromes with mutations in SH2DlA/DSHP/SAPgene. The dramatic increase of the risk or B-cell lymphoma development in XLP1 patients is linked not only to SAP deficiency of NK, NKT and T cells, but probably to the impairment of B cell differentiation. Aim - to analyze the receptor-mediated Akt/PKB and ERK1/2 phosphorylation and expression of transcription factors that are involved in B cell maturation in EBV-transformed B-lymphoblastoid cell lines (B-LCLs) from XLP1 patients (XLP B-LCLs) in comparison with conventional B-LCLs. Studies were performed on EBV-transformed XLP B-LCLs 1ARC 739, SC-XLP and RP-XLP in comparison with SAP-negative B-LCLT5-1 and SAP-positive B-LCL MP-1. Western blot analysis was used for evaluation of Akt (Ser473) and ERK1/2 (Thr202/Tyr204) phosphorylation in response to ligation of CD150, CD40, and IgM cell surface receptors. The expression levels of transcription factors IRF4, IRF8, BCL6, BLIMP1, SPIB, PU.l and MITF were assessed using quantitative RT-PCR. It was shown that SAP deficiency in XLP B-LCL did not abrogate CD150-mediated Akt and ERK1/2 phos-phorylation. At the same time, ligation of CD150 or IgM affects kinetics and amplitude or ERK1/2 activation. In XLP B-LCL the CD150 signaling with IgM coligation play the dominant role in both Akt and ERK1/2 phosphorylation. We found that significantly reduced IRF4, 1RK8 and PU.l expression levels are the key features of XLP B-LCLs. Conclusion: XLP B-LCLs and conventional B-LCLs have differences in kinetics and amplitude of Akt and ERK1/2 phosphorylation. Analysis of transcription factors profile revealed the distinguishing features of XLP B-LCLs with SAP deficiency that may impair B cell differentiation.

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