Age-related thymic involution is characterized by a decrease in thymic epithelial cell (TEC) number and function parallel to a disruption in their spatial organization, resulting in defective thymocyte development and proliferation as well as peripheral T cell dysfunction. Deficiency of , an antiaging gene and modifier of fibroblast growth factor signaling, causes premature aging. To investigate the role of in accelerated age-dependent thymic involution, we conducted a comprehensive analysis of thymopoiesis and peripheral T cell homeostasis using -deficient () mice.
View Article and Find Full Text PDFMyeloid-derived suppressor cells (MDSCs) are a well-defined population of cells that accumulate in the tissue of tumor-bearing animals and are known to inhibit immune responses. Within 4 days, bone marrow cells cultured in granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor resulted in the generation of CD11b(+)Ly6G(lo)Ly6C(+) MDSCs, the majority of which are interleukin-4Rα (IL-4Rα(+)) and F4/80(+). Such MDSCs potently inhibited in vitro allogeneic T-cell responses.
View Article and Find Full Text PDFRas plays an important role in B cell development. However, the stage at which Ras governs B cell development remains unclear. Moreover, the upstream receptors and downstream effectors of Ras that govern B cell differentiation remain undefined.
View Article and Find Full Text PDFThe NF-kappaB signaling pathway plays a critical role in regulating innate and adaptive immunity. This is clearly evident as mouse models deficient for numerous NF-kappaB subunits and upstream activators exhibit defects in the immune system ranging from impaired development of lymphocytes to defective adaptive immune responses. In this review, we focus on the role that NF-kappaB plays in the germinal center (GC) reaction.
View Article and Find Full Text PDFChronic myelogenous leukemia is a malignant disease of the hematopoietic stem cell compartment, which is characterized by expression of the BCR-ABL fusion protein. Expression of BCR-ABL allows myeloid cells to grow in the absence of the growth factors interleukin-3 and granulocyte-macrophage colony-stimulating factor. The tyrosine kinase activity of BCR-ABL constitutively activates signaling pathways associated with Ras and its downstream effectors and with the Jak/STAT pathway.
View Article and Find Full Text PDFAllelic exclusion prevents pre-B cells from generating more than one functional H chain, thereby ensuring the formation of a unique pre-BCR. The signaling processes underlying allelic exclusion are not clearly understood. IL-7R-dependent signals have been clearly shown to regulate the accessibility of the Ig H chain locus.
View Article and Find Full Text PDFThe molecular mechanisms regulating lymphocyte lineage commitment remain poorly characterized. To explore the role of the IL7R in this process, we generated transgenic mice that express a constitutively active form of STAT5 (STAT5b-CA), a key downstream IL7R effector, throughout lymphocyte development. STAT5b-CA mice exhibit a 40-fold increase in pro-B cells in the thymus.
View Article and Find Full Text PDFSignals initiated by the IL7R are required for B cell development. However, the roles that distinct IL7R-induced signaling pathways play in this process remains unclear. To identify the function of the Raf and STAT5 pathways in IL7R-dependent B cell development, we used transgenic mice that express constitutively active forms of Raf (Raf-CAAX) or STAT5 (STAT5b-CA) throughout lymphocyte development.
View Article and Find Full Text PDFUsing transgenic mice that express a constitutively active version of STAT5b, we demonstrate that STAT5 plays a key role in governing B cell development and T cell homeostasis. STAT5 activation leads to a 10-fold increase in pro-B, but not pro-T, cells. Conversely, STAT5 signaling promotes the expansion of mature alphabeta T cells (6-fold increase) and gammadelta and NK T cells (3- to 4-fold increase), but not of mature B cells.
View Article and Find Full Text PDFActivation of the serine/threonine kinase c-Raf-1 requires membrane localization, phosphorylation, and oligomerization. To study these mechanisms of Raf activation more precisely, we have used a membrane-localized fusion protein, myr-Raf-GyrB, which can be activated by coumermycin-induced oligomerization in NIH3T3 transfectants. By introducing a series of point mutations into the myr-Raf-GyrB kinase domain (S338A, S338A/Y341F, Y340F/Y341F, and T491A/S494A) we can separately study the role that membrane localization, phosphorylation, and oligomerization play in the process of Raf activation.
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