Pillars article: the CD4 receptor is complexed in detergent lysates to a protein-tyrosine kinase (pp58) from human T lymphocytes. 1988.

The CD4 (T4) antigen is a cell-surface glycoprotein that is expressed predominantly on the surface of helper T cells and has been implicated in the regulation of T-cell activation and in the associative recognition of class II antigens of the major histocompatibility complex. In addition, the CD4 antigen appears to serve as a receptor for the human immunodeficiency virus (HIV). An important question has been whether the CD4 receptor is linked to an intracellular mediator that could regulate the activation of the CD4 subset.

CD molecules 2005: human cell differentiation molecules.

The immune system works through leukocytes interacting with each other, with other cells, with tissue matrices, with infectious agents, and with other antigens. These interactions are mediated by cell-surface glycoproteins and glycolipids. Antibodies against these leukocyte molecules have provided powerful tools for analysis of their structure, function, and distribution.

Siva-1 binds to and inhibits BCL-X(L)-mediated protection against UV radiation-induced apoptosis.

We previously cloned Siva-1 by using the cytoplasmic tail of CD27, a member of the tumor necrosis factor receptor family, as the bait in the yeast two-hybrid system. The Siva gene is organized into four exons that code for the predominant full-length Siva-1 transcript, whereas its alternate splice form, Siva-2, lacks exon 2 coding sequence. Various groups have demonstrated a role for Siva-1 in several apoptotic pathways.

Impaired apoptosis, extended duration of immune responses, and a lupus-like autoimmune disease in IEX-1-transgenic mice.

Susceptibility of activated T cells to apoptosis must be tightly regulated to ensure sufficient T cell progeny for an effective response, while allowing a rapid depletion of them at the end of the immune response. We show here that a previously isolated, NF-kappa B/rel target gene IEX-1 (Immediate Early response gene X-1) is highly expressed in T cells at early stages of activation, but declines with a prolonged period of activation time, coincident with an increased susceptibility of T cells to apoptosis during the late phases of an immune response. Transgenic expression of IEX-1 specifically in lymphocytes impaired apoptosis in activated T cells, extended a duration of an effector-phase of a specific immune response, and increased the accumulation of effector/memory-like T cells and the susceptibility to a lupus-like autoimmune disease.

CD26-mediated signaling for T cell activation occurs in lipid rafts through its association with CD45RO.

CD26 is a T cell activation antigen that contains dipeptidyl peptidase IV activity and is known to bind adenosine deaminase. The mechanism by which CD26 costimulation potentiates T cell receptor-mediated T cell activation, leading to subsequent exertion of T cell effector function, is still not clearly defined. In this article, we demonstrate that CD26 localizes into lipid rafts, and targeting of CD26 to rafts is necessary for signaling events through CD26.

Molecular cloning of Porimin, a novel cell surface receptor mediating oncotic cell death.

Anti-Porimin (Pro-oncosis receptor inducing membrane injury) mAb mediates oncosis-like cell death in Jurkat cells. Porimin cDNA was isolated from a Jurkat cell cDNA library by COS cell-expression cloning. The 3,337-bp cDNA has an ORF of 567 bp, encoding a type I transmembrane protein of 189 amino acids.

B cell co-receptors regulating T cell-dependent antibody production in common variable immunodeficiency: CD27 pathway defects identify subsets of severely immuno-compromised patients.

CD27 and CD134 ligand (CD134L) are two B cell co-receptors for T(h) cell activation-induced ligands (i.e. CD70 and CD134) that promote differentiation of B cells into plasma cells and high-rate antibody production respectively.

Monoclonal antibodies derived from BALB/c mice immunized with apoptotic Jurkat T cells recognize known autoantigens.

It has been postulated that post-translational modifications and relocalization of proteins during apoptosis may lead to presentation of these molecules to the immune system in such a way that normal mechanisms of tolerance are bypassed. In the present study, Jurkat cells were induced to undergo apoptosis by treatment with the chemotherapeutic agent Ara-C. BALB/c mice were then immunized with the apoptotic cells and hybridomas were generated.

Defective surface expression of attractin on T cells in patients with common variable immunodeficiency (CVID).

The proliferative responses of T lymphocytes of a subset of patients with CVID are abnormally low. This may be due to abnormalities in extracellular interactions or signalling defects downstream from membrane-associated receptors. Demonstrating that the T cell receptor signalling was normal, we observed no abnormal pattern of activation-induced tyrosine phosphorylation in cells from CVID patients.

CD134L engagement enhances human B cell Ig production: CD154/CD40, CD70/CD27, and CD134/CD134L interactions coordinately regulate T cell-dependent B cell responses.

CD134 is a member of the TNFR family expressed on activated T cells, whose ligand, CD134L, is found preferentially on activated B cells. We have previously reported that the CD70/CD27 interaction may be more important in the induction of plasma cell differentiation after the expansion phase induced by the CD154/CD40 interaction has occurred. When CD134-transfected cells were added to PBMCs stimulated with pokeweed mitogen, IgG production was enhanced in a dose-dependent fashion.

A biochemical function for attractin in agouti-induced pigmentation and obesity.

Agouti protein, a paracrine signaling molecule normally limited to skin, is ectopically expressed in lethal yellow (A(y)) mice, and causes obesity by mimicking agouti-related protein (Agrp), found primarily in the hypothalamus. Mouse attractin (Atrn) is a widely expressed transmembrane protein whose loss of function in mahogany (Atrn(mg-3J)/ Atrn(mg-3J)) mutant mice blocks the pleiotropic effects of A(y). Here we demonstrate in transgenic, biochemical and genetic-interaction experiments that attractin is a low-affinity receptor for agouti protein, but not Agrp, in vitro and in vivo.

Biochemical and genetic studies of pigment-type switching.

Mutations that affect the balance between the synthesis of eumelanin and pheomelanin provide a powerful set of tools with which to understand general aspects of cell signaling. Previous work from our laboratory has demonstrated that pheomelanin synthesis is triggered by the ability of Agouti protein to inhibit signaling through the Melanocortin 1 receptor (Mc1r). In a bioassay based on the Xenopus Mc1r, Agouti protein has two effects, competitive inhibition of receptor occupancy by alpha-MSH and down-regulation of receptor signaling, which are mediated separately by domains in the amino- and carboxy-terminal regions of Agouti protein, respectively.

Internalization of CD26 by mannose 6-phosphate/insulin-like growth factor II receptor contributes to T cell activation.

CD26 is a T cell activation antigen known to bind adenosine deaminase and have dipeptidyl peptidase IV activity. Cross-linking of CD26 and CD3 with immobilized mAbs can deliver a costimulatory signal that contributes to T cell activation. Our earlier studies revealed that cross-linking of CD26 induces its internalization, the phosphorylation of a number of proteins involved in the signaling pathway, and subsequent T cell proliferation.

Attractin: a cub-family protease involved in T cell-monocyte/macrophage interactions.

Attractin is a rapidly upregulated membrane-associated molecule on activated T cells. It is a member of the CUB family of extracellular guidance and development proteins, sharing with them a protease activity similar to that of Dipeptidyl peptidase IV (DPPIV/CD26). Most remarkably, and in sharp contrast to CD26, it is released from the T cell and is presumed to be a major source of a soluble serum-circulating attractin.

Secreted and membrane attractin result from alternative splicing of the human ATRN gene.

Attractin, initially identified as a soluble human plasma protein with dipeptidyl peptidase IV activity that is expressed and released by activated T lymphocytes, also has been identified as the product of the murine mahogany gene with connections to control of pigmentation and energy metabolism. The mahogany product, however, is a transmembrane protein, raising the possibility of a human membrane attractin in addition to the secreted form. The genomic structure of human attractin reveals that soluble attractin arises from transcription of 25 sequential exons on human chromosome 20p13, where the 3' terminal exon contains sequence from a long interspersed nuclear element-1 (LINE-1) retrotransposon element that includes a stop codon and a polyadenylation signal.

Murine Siva-1 and Siva-2, alternate splice forms of the mouse Siva gene, both bind to CD27 but differentially transduce apoptosis.

CD27, a member of the TNFR family known to provide essential co-stimulatory signals for T cell growth and B cell Ig synthesis, can also mediate cell death. Using the CD27 cytoplasmic tail as the bait in yeast two hybrid assay, we previously cloned human Siva, a pro-apoptotic molecule. Here we report the characterization of the mouse Siva gene as a 4 kb sequence containing 4 exons and 3 introns.

Functional interaction of DFF35 and DFF45 with caspase-activated DNA fragmentation nuclease DFF40.

DNA fragmentation factor (DFF) functions downstream of caspase-3 and directly triggers DNA fragmentation during apoptosis. Here we described the identification and characterization of DFF35, an isoform of DFF45 comprised of 268 amino acids. Functional assays have shown that only DFF45, not DFF35, can assist in the synthesis of highly active DFF40.

CD26/dipeptidyl peptidase IV differentially regulates the chemotaxis of T cells and monocytes toward RANTES: possible mechanism for the switch from innate to acquired immune response.

CD26, a 110 kDa cell surface glycoprotein, exhibits dipeptidyl peptidase IV (DPPIV; EC 3.4.14.

The mouse mahogany locus encodes a transmembrane form of human attractin.

Agouti protein and agouti-related protein are homologous paracrine signalling molecules that normally regulate hair colour and body weight, respectively, by antagonizing signalling through melanocortin receptors. Expression of Agouti is normally limited to the skin, but rare alleles from which Agouti is expressed ubiquitously, such as lethal yellow, have pleiotropic effects that include a yellow coat, obesity, increased linear growth, and immune defects. The mahogany (mg) mutation suppresses the effects of lethal yellow on pigmentation and body weight, and results of our previous genetic studies place mg downstream of transcription of Agouti but upstream of melanocortin receptors.

Immune regulatory loops determine productive interactions within human T lymphocyte-dendritic cell clusters.

Help for the induction of cytolytic T lymphocytes is mediated by dendritic cells (DC) that are conditioned by CD40 signaling. We identified tumor necrosis factor family member CD27L/CD70, which is expressed by cytolytic T lymphocytes on interaction with DC to control CD154 (CD40L) up-regulation on CD45RA+ helper T cells for subsequent DC stimulation. The results show that the initiation of a cytolytic immune response is determined by regulatory circuits, requiring simultaneous activation and differentiation of all cells involved in T lymphocyte-DC cluster formation.

APO2.7 defines a shared apoptotic-necrotic pathway in a breast tumor hypoxia model.

A breast tumor hypoxia model used to simulate conditions which may exist within an enlarging tumor was examined using documented methods for identifying mechanisms of cell death and compared to the mitochondrial membrane-specific APO2.7 antigen expression. Hypoxic conditions were induced by holding cell pellets of MDA-MB-175-VII breast carcinoma cells in tightly capped centrifuge tubes for up to 10 days.