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The NF-AT family of transcription factors activates early immune response genes such as cytokines. In the adult, NF-ATc is expressed exclusively in the lymphoid system and is induced upon lymphocyte activation. NF-ATc null mutant mice die in utero of cardiac failure, precluding analysis of the role of NF-ATc in lymphocyte activation. By using RAG-2-deficient blastocyst complementation, we now demonstrate...
The origin of hematopoietic stem cells (HSCs) and their growth factor requirement are poorly understood. Here we describe a new in vitro culture system of the aorta-gonad-mesonephros (AGM) region, where long-term repopulating HSCs first arise. We demonstrate that oncostatin M (OSM) is expressed in the AGM and is absolutely required for the expansion of multipotential hematopoietic progenitors in vitro...
It is known that T cells engage antigen-presenting cells (APCs) in a stable interaction that results in sustained TCR signaling. We show here that the duration of this process is critical in determining whether T cellswill be activated or deleted. Whereas naive T cells require approximately 20 hr of sustained signaling to be committed to proliferation, effector T cells become committed after only...
NF-Atc1 is a member of a family of genes that encodes the cytoplasmic component of the nuclear factor of activated T cells (NF-AT). In activated T cells, nuclear NF-AT binds to the promoter regions of multiple cytokine genes and induces their transcription. The role of NF-Atc1 was investigated in recombination activating gene-1 (RAG-1)-deficient blastocyst complementation assays using homozygous NF-Atc1-/-...
Deletion of antigen-activated T cells after an immune response and during peripheral negative selection after strong T cell receptor (TCR) engagement of cycling T cells occurs by an apoptotic process termed TCR antigen-induced cell death (AID). By analyzing the timing of death, cell cycle markers, BrdU-labeled S phase cells, and phase-specific centrifugally elutriated cultures from stimulated Jurkat...
Herpes simplex virus (HSV) 1 and 2 infect activated T lymphocytes by attachment of the HSV envelope glycoprotein D (gD) to the cellular herpesvirus entry mediator (HVEM), an orphan member of the tumor necrosis factor receptor superfamily. Here, we demonstrate that HVEM binds two cellular ligands, secreted lymphotoxin α (LTα) and LIGHT, a new member of the TNF superfamily. LIGHT is a 29 kDa type II...
Expression of the avian chT1 thymocyte antigen persists on a subpopulation of peripheral T cells enriched in the DNA deletion circles created by αβ and γδ TCR gene rearrangements. The chT1 + cells are evenly distributed among all of the peripheral T lymphocyte compartments. The levels of chT1 + T cells in the periphery gradually decline in parallel with age-related thymic involution,...
Lymphoid enhancer factor 1 (LEF-1) and T cell factor 1 (TCF-1) are closely related transcription factors that are both expressed during murine T cell differentiation and that regulate the T cell receptor α (TCRα) enhancer in transfection assays. Targeted gene disruption of either the Tcf1 or Lef1 gene in mice did not affect TCRα gene expression and resulted in an incomplete defect or no defect in...
A cDNA clone encoding the human homolog of rat Jagged1 was isolated from normal human marrow. Analyses of human stromal cell lines indicate that this gene, designated hJagged1, is expressed by marrow stromal cells typified by the cell line HS-27a, which supports the long-term maintenance of hematopoietic progenitor cells. G-CSF-induced differentiation of 32D cells expressing Notch1 was inhibited by...
Thymus-derived glucocorticoids antagonize T cell receptor (TCR)-induced thymocyte apoptosis, allowing the survival (positive selection) of cells bearing TCRs that recognize self antigens with low-to-moderate avidity. Here we demonstrate that expression of an antisense glucocorticoid receptortransgene in thymocytes of spontaneously autoimmune MRL-Ipr/Ipr mice causes the loss of specific TCR Vβ-bearing...
Type 2 nitric oxide synthase (NOS2) is required for the Th1-dependent healing of infections with intracellular microbes, including Leishmania major. Here, we demonstrate the expression and define the function of NOS2 during the innate response to L. major. At day 1 of infection, genetic deletion or functional inactivation of NOS2 abolished the IFNγ and natural killer cell response, increased the expression...
The MAP kinase (MAPK) JNK but not ERK is synergistically activated during costimulation of T cells. We examined how protein tyrosine kinases (PTKs) and GTPases differentially regulate JNK and ERK in T cells. While PTKs are not selective, small GTPases display distinct MAPK-activating functions. Whereas Ras activates ERK, Rac activates JNK. Rac cooperates with a Syk-generated signal to enhance JNK...
During LCMV infection, CD8 + T cells expand greatly. Bystander activation has been thought to play a role because few cells score as LCMV specific in limiting dilution analysis. In contrast, we find that at least a quarter of the CD8 + cells secrete IFNγ specifically in response to LCMV peptides at the peak of the response. Moreover, by analyzing the expansion of adoptively transferred...
Anti-Sm and anti-ssDNA transgenic (Tg) mice were generated using the V H -D-J H rearrangement of an anti-Sm hybridoma of MRL/Mp-Ipr/Ipr origin. B cells of each specificity account for 15%-35% of the splenic repertoire, but no circulating anti-Sm or anti-ssDNA antibodies are detected. Most autoreactive cells exhibit an immature B cell phenotype and have short half-lives equivalent to...
HLA-DM catalyzes the release of MHC class Il-associated invariant chain-derived peptides (CLIP) from class II molecules. Recent evidence has suggested that HLA-DO is a negative regulator of HLA-DM in B cells, but the physiological function of HLA-DO remains unclear. Analysis of antigen presentation by B cells from mice lacking H2-O (the mouse equivalent of HLA-DO), together with biochemical analysis...
Within the pools of μH chain-producing precursor and mature B cells from normal and λ5-defective mice, the frequency of cells in which both H chain alleles were productively V H DJ H rearranged was determined. An equally high percentage (2%-4%) of cells carrying two productively V H DJ H -rearranged H chain loci was found in precursor and mature B cell pools of both...
Although IL-4 induces expulsion of the gastrointestinal nematode parasite, Nippostrongylus brasiliensis, from immunodeficient mice, this parasite is expelled normally by IL-4-deficient mice. This apparent paradox is explained by observations that IL-4 receptor α chain (IL-4Rα)-deficient mice and Stat6-deficient mice fail to expel N. brasiliensis, and a specific antagonist for IL-13, another activator...
CIITA is the mediator of MHC class II gene induction byinterferon-γ (IFNγ). The CIITA gene is itself selectively activated via one of its four promoters (PIV). We show here that three cis-acting elements, the GAS, the E box, and the IRF-1-binding site, as well as the trans-acting factors Stat1 and IRF-1, are essential for activation of CIITA promoter IV by IFNγ. Stat1 binds to the GAS site only in...
We have examined the role of Fas and Bcl-2 in T cell survival and responses to antigen in vivo using T cells that express a transgenic antigen receptor specific for hen egg lysozyme (HEL) and that either lack functional Fas or Fas ligand (FasL) or overexpress Bcl-2 as a transgene. HEL-specific, Bcl-2-transgenic T cells showed prolonged responses to immunization with cognate peptide but were eliminated...
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