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Superantigens (SAGs) are a class of immunostimulatory proteins of bacterial or viral origin that activate T cells by binding to the Vβ domain of the T cell antigen receptor (TCR). The three-dimensional structure of the complex between a TCR β chain (mouse Vβ8.2) and the SAG staphylococcal enterotoxin B (SEB) at 2.4 Å resolution reveals why SEB recognizes only certain Vβ families, as well as why only...
GPI-linked proteins coassociate with intracellular tyrosine kinases in “lipid rafts” proposed to function as platforms for signal transduction and cytoskeletal reorganization. TCR activation requires both tyrosine kinase signals and cytoskeletal reorganization. How receptor engagement initiates cytoskeletal changes remains poorly understood. We investigated the consequences of recruiting GPI-linked...
The transcription factor RelB had been shown to be important for dendritic cell (DC) development, but the type of DC involved was not clear. Here, we report that RelB mRNA is expressed strongly in CD8α − DEC-205 − DC but only weakly in CD8α + DEC-205 + DC. In addition, CD8α + DEC-205 + DC are present and functional in RelB null mice, the DC deficiency...
We have identified RORγt, a novel, thymus-specific isoform of the orphan nuclear receptor RORγ that is expressed predominantly in CD4 + CD8 + double-positive thymocytes. Ectopic expression of RORγt protects T cell hybridomas from activation-induced cell death by inhibiting the upregulation of Fas ligand. Following hybridoma stimulation, RORγt also inhibits IL-2 production but does...
The action of adenoviral E1A oncoprotein on host immune-response genes has been attributed to interaction with p300/CBP-type transcriptional coactivators in competition with endogenous transcription factors such as signal transducer and activator of transcription (STAT) proteins. However, we show that mutant forms of E1A that no longer bind p300/CBP can still interact directly with Stat1 (via E1A...
We describe a model system for class switch recombination (CSR) using CH12F3-2 cells transfected with a DNA construct containing two S sequences transcribed by different promoters and separated by a viral thymidine kinase (TK) gene. Recombination observed using this system shares key properties with physiological CSR: deletion of DNA between two S regions, requirement for cytokine stimulation, and...
We have examined binding characteristics for a single TCR interacting with five of its different peptide/MHC ligands using surface plasmon resonance. We find that very small structural changes produce ligands with similar equilibrium binding affinities (K D ) for the TCR, but vastly different potencies for T cell activation. Ligands with similar K D s induce similar amounts of total...
The Notch receptor and its ligands are involved in many developmental processes. They are highly expressed in the thymus and have been implicated in the CD4 versus CD8 lineage decision. We identified the constitutively active intracellular fragment of murine Notch-1 as capable of rendering thymomas resistant to glucocorticoid-induced apoptosis. This effect was confirmed in other T cell lines and in...
Searching for an in vitro model for somatic hypermutation, we have identified an IgM-expressing Burkitt lymphoma line that constitutively diversifies its immunoglobulin V domain at high rate during culture. As in in vivo, the mutations are largely nucleotide substitutions with the pattern of substitutions revealing a component of the human hypermutation program that is preferentially targeted to G/C...
Differentiating cells undergo programmed alterations in their patterns of gene expression, which are often regulated by structural changes in chromatin. Here we demonstrate that T cell differentiation results in long-range changes in the chromatin structure of effector cytokine genes, which persist in resting Th1 and Th2 cells in the absence of further stimulation. Differentiation of naive T helper...
Despite years of investigation, precursor-progeny relationships within the developing lymphoid lineages of the hematopoietic system remain poorly defined. We have characterized the potential of precursors found within a subpopulation of fetal liver defined by AA4.1 and FcγRII/III expression and predominantly restricted to lymphoid and macrophage development. When cultured in methylcellulose with appropriate...
Mammalian serine/threonine-linked oligosaccharides (O-glycans) are commonly synthesized with the Golgi enzyme core 2 β-1,6-N-acetylglucosaminyltransferase (C2 GlcNAcT). Core 2 O-glycans have been hypothesized to be essential for mucin production and selectin ligand biosynthesis. We report that mice lacking C2 GlcNAcT exhibit a restricted phenotype with neutrophilia and a partial deficiency of selectin...
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