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Transcriptional pathways controlling the development of [CD44.sup.hi] memory phenotype (MP) T cells with 'innate-like' functions are not well understood. Here we show that the BTB (bric-a-brac, tramtrack, broad complex) domain-containing protein promyelocytic leukemia zinc finger (PLZF) is expressed in [CD44.sup.hi], but not in [CD44.sup.lo], [CD4.sup.+] T cells. Transgenic expression of PLZF during T cell development and in [CD4.sup.+] and [CD8.sup.+] T cells induced a T cell intrinsic program leading to an increase in peripheral [CD44.sup.hi] MP [CD4.sup.+] and [CD8.sup.+] T cells and a corresponding decrease of naive [CD44.sup.lo] T cells. The MP [CD4.sup.+] and [CD8.sup.+] T cells produced IFN[gamma] upon PMA/ionomycin stimulation, thus showing innate-like function. Changes in the naive versus memory-like subset distribution were already evident in single-positive thymocytes, indicating PLZF-induced T cell developmental alterations. In addition, CDld-restricted natural killer T cells in PLZF transgenic mice showed impaired development and were severely reduced in the periphery. Finally, after anti-CD3/ CD28 stimulation, [CD4.sup.+] transgenic T cells showed reduced IL-2 and IFN[gamma], production but increased IL-4 secretion as a result of enhanced IL-4 production of the [CD44.sup.hi][CD62L.sup.+] subset. Our data indicate that PLZF is a novel regulator of the development of [CD44.sup.hi] MP T cells with a characteristic partial innate-like phenotype. innate-like lymphocytes | T cell development | transgenics

Dasatinib is a small-molecule kinase inhibitor used for the treatment of imatinib-resistant chronic myelogenous leukemia (CML). We have analyzed the kinases targeted by dasatinib by using an unbiased chemical proteomics approach to detect binding proteins directly from lysates of CML cells. Besides Abl and Src kinases, we have identified the Tec kinases Btk and Tec, but not Itk, as major binders of dasatinib. The kinase activity of Btk and Tec, but not of Itk, was inhibited by nanomolar concentrations of dasatinib in vitro and in cultured cells. We identified the gatekeeper residue as the critical determinant of dasatinib susceptibility. Mutation of Thr-474 in Btk to lie and Thr-442 in Tec to lie conferred resistance to dasatinib, whereas mutation of the corresponding residue in Itk (Phe-435) to Thr sensitized the otherwise insensitive Itk to dasatinib. The configuration of this residue may be a predictor for dasatinib sensitivity across the kinome. Analysis of mast cells derived from Btk-deficient mice suggested that inhibition of Btk by dasatinib may be responsible for the observed reduction in histamine release upon dasatinib treatment. Furthermore, dasatinib inhibited histamine release in primary human basophils and secretion of proinflammatory cytokines in immune cells. The observed inhibition of Tec kinases by dasatinib predicts immunosuppressive (side) effects of this drug and may offer therapeutic opportunities for inflammatory and immunological disorders. kinase inhibitor | leukemia | Tec kinases

Cd8a and Cd8b1 coreceptor gene (Cd8) expression is tightly controlled during T-cell development by the activity of five Cd8 enhancers (E8I-E8V). Here we demonstrate a unique transcriptional program regulating CD8 expression during CD8+ effector T-cell differentiation. The Cd8 enhancer E8I and Runx/core-binding factor-β (CBFβ) complexes were required for the establishment of this regulatory circuit, because E8I-, Runx3-, or CBFβ-deficient CD8+ T cells down-regulated CD8α expression during activation. This finding correlated with enhanced repressive histone marks at the Cd8a promoter in the absence of E8I, and the down-regulation of CD8α expression could be blocked by treating E8I-, Runx3-, or CBFβ-deficient CD8+ T cells with the histone deacetylase inhibitor trichostatin A. Moreover, Runx/CBFβ complexes bound the Cd8ab gene cluster in activated CD8+ T cells, suggesting direct control of the Cd8a locus. However, CD8+ effector T cells maintained high levels of CD8α when CBFβ was conditionally deleted after activation. Thus, our data suggest an E8I- and Runx3/CBFβ-dependent epigenetic programming of the Cd8a locus during T-cell activation, leading to Runx/CBFβ complex-independent maintenance of CD8α expression in effector T cells. [ABSTRACT FROM AUTHOR]

Cd8a and Cd8b1 coreceptor gene (Cd8) expression is tightly controlled during T-cell development by the activity of five Cd8 enhancers (E8(I)-E8(V)). Here we demonstrate a unique transcriptional program regulating CD8 expression during CD8(+) effector T-cell differentiation. The Cd8 enhancer E8(I) and Runx/core-binding factor-β (CBFβ) complexes were required for the establishment of this regulatory circuit, because E8(I)-, Runx3-, or CBFβ-deficient CD8(+) T cells down-regulated CD8α expression during activation. This finding correlated with enhanced repressive histone marks at the Cd8a promoter in the absence of E8(I), and the down-regulation of CD8α expression could be blocked by treating E8(I)-, Runx3-, or CBFβ-deficient CD8(+) T cells with the histone deacetylase inhibitor trichostatin A. Moreover, Runx/CBFβ complexes bound the Cd8ab gene cluster in activated CD8(+) T cells, suggesting direct control of the Cd8a locus. However, CD8(+) effector T cells maintained high levels of CD8α when CBFβ was conditionally deleted after activation. Thus, our data suggest an E8(I)- and Runx3/CBFβ-dependent epigenetic programming of the Cd8a locus during T-cell activation, leading to Runx/CBFβ complex-independent maintenance of CD8α expression in effector T cells.