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Diagnosis of blastic plasmacytoid dendritic cell neoplasm (BPDCN) or plasmacytoid dendritic cell leukemia (pDCL) is mainly based on immunophenotypical characterization of leukemic cells in blood or bone marrow samples. We tested by flow cytometry intracellular expression of the proto-oncogene T-cell leukemia 1 (TCL1), as well as membrane and intracellular expression of immunoglobulin-like transcript 7 (ILT7) in 21 pDCL samples and 61 non-pDC acute leukemia samples [i.e., 14 B-acute lymphoblastic leukemia (B-ALL), 9 T-ALL and 38 acute myeloid leukemia (AML)]. TCL1 is highly expressed in all pDCL samples while at a statistically lower level in all B-ALL and 34% of AML. Statistical analysis shows that intensity of TCL1 expression is a good marker for differential diagnosis of pDCL versus other acute leukemia (area under the receiver-operating characteristic curve, [AUC]: 0.96). By contrast, ILT7 positivity is limited to few pDCL samples and cannot be useful for diagnosis purpose. In conclusion, high intracellular intensity of TCL1 expression is currently the best marker for pDC lineage assignment by flow cytometry, which is particularly useful to distinguish pDCL from CD4(+) CD56(+/-) undifferentiated or monoblastic acute leukemia. Thus, intracellular TCL1 detection should be included in acute leukemia diagnosis panels used in hematology laboratories. © 2012 International Society for Advancement of Cytometry., (Copyright © 2012 International Society for Advancement of Cytometry.)

The VLA-4 integrin supports static cell-cell, cell-matrix adhesion, and dynamic interactions with VCAM-1. Although functions for well-conserved beta(1) integrin cytoplasmic domains in regulating static cell adhesion has been established, the molecular basis for beta(1) integrin-dependent arrest on VCAM-1 under flow conditions remains poorly understood. We have transfected the beta(1) integrin-deficient A1 Jurkat T cell line with beta(1) cDNA constructs with deletions of the NPXY motifs and specific mutations of tyrosine residues. Deletion of either NPXY motif impaired static adhesion induced by CD2 or CD47 triggering or direct beta(1) integrin stimulation. In contrast, PMA-induced adhesion to VCAM-1 was unaffected by deletion of the NPIY motif and only slightly impaired by deletion of NPKY. Moreover, deletion of the NPIY motif resulted in enhanced rolling and reduced arrest on VCAM-1 under shear flow conditions. In contrast, deletion of the NPKY motif did not alter arrest under flow. Although tyrosine to phenylalanine substitutions within two NPXY motifs did not alter static adhesion to VCAM-1, these mutations enhanced arrest on VCAM-1 under flow conditions. Furthermore, although deletion of the C'-terminal 5 AA of the beta(1) cytoplasmic domain dramatically impaired activation-dependent static adhesion, it did not impair arrest on VCAM-1 under flow conditions. Thus, our results demonstrate distinct structural requirements for VLA-4 function under static and shear flow conditions. This may be relevant for VLA-4 activity regulation in different anatomic compartments, such as when circulating cells arrest on inflamed endothelium under shear flow and when resident cells in bone marrow interact with VCAM-1- positive stromal cells.