Genetic data show that Carcharhinus tilstoni is not confined to the tropics, highlighting the importance of a multifaceted approach to species identification.

This study shows a range extension for the Australian blacktip shark Carcharhinus tilstoni, which was believed to be restricted to Australia's tropical waters, of >1000 km into temperate waters, revealing its vulnerability to a wider commercial fishery.

T cell regulation of p62(dok) (Dok1) association with Crk-L.

In addition to engagement of the T cell receptor-CD3 complex, T lymphocytes can be activated by a variety of cell surface molecules including the approximately 50-kDa surface receptor CD2. While the majority of biochemical signaling elements are triggered by either CD2 or TcR-CD3 receptors, a small number of proteins are engaged by only one receptor. Recently, p62(dok) (Dok1), a member of the Dok family of adapter molecules, has been reported to be activated by CD2 and not by CD3 engagement. Here we have examined the role of p62(dok) in CD2-dependent signaling in Jurkat T cells. As previously reported, we find that ligation of the CD2 molecule by mitogenic pairs of anti-CD2 mAbs led to phosphorylation of p62(dok). While CD2-induced p62(dok) tyrosine phosphorylation was independent of both the p36/38 membrane adapter protein linker of activated T cells (LAT) and the ZAP70/Syk family of kinases, it was dependent upon the Src family of kinases including Lck and Fyn. We find further that CD2 engagement induced the association of tyrosine-phosphorylated p62(dok) to Crk-L. The CD2-dependent association of p62(dok) to Crk-L was independent of expression of the ZAP70/Syk family of kinases. Of note, while T cell receptor-CD3 engagement did not induce either p62(dok) phosphorylation or Crk-L association in Jurkat T cells, it did inhibit CD2-dependent p62(dok)-Crk-L complexes; this TcR-CD3-mediated regulation was dependent upon ZAP70 kinase activity. Our data suggest that phosphorylation of p62(dok) and its interaction with other signaling proteins may depend upon integrated signals emanating from the CD2 receptor, utilizing a ZAP70/LAT-independent pathway, and the TcR-CD3 receptor, which is ZAP70/Syk-dependent.

Regeneration and tolerance factor is expressed during T-lymphocyte activation and plays a role in apoptosis.

Regeneration and tolerance factor (RTF) is a protein cloned from the thymus and expressed on B lymphocytes in normal pregnancy, B lymphocytic leukemia lines, and T and B lymphocytes in individuals with HIV infection. Findings, using the Jurkat T-cell model, revealed that RTF is upregulated after activation and anti-RTF antibody-induced apoptosis. In this article anti-RTF antibody-induced apoptosis of both unstimulated and activated T lymphocytes. RTF expression was examined in human PBMC or purified T lymphocytes after their in vitro activation. Kinetic studies indicated maximal RTF cell surface expression on activated T lymphocytes occurred between expression of the early activation antigen CD69 and the IL-2alpha receptor (CD25) by multiparameter flow cytometry. RTF receptor expression correlated with Fas (CD95) and CD25 receptor expression (r2 = 0.6 and 0.5, respectively). RTF surface expression was dependent on the stimuli used to activate T lymphocytes. T lymphocytes obtained maximal RTF expression when activated through the TCR signal complex using anti-CD3epsilon antibody alone when compared with T lymphocytes activated with costimulation provided by anti-CD28 antibody alone or with anti-CD28 and anti-CD3epsilon antibody. RTF is expressed under conditions of both activation and anergy. The RTFs increased concentration on the surface of anergic T cells may protect these cells from apoptosis because increased RTF concentrations inhibited anti-RTF induced apoptosis. These data further characterize the expression of RTF on activated T lymphocytes and the role of anti-RTF antibody in T-lymphocyte apoptosis.

Regeneration and tolerance factor of the human placenta induces IL-10 production.

Regeneration and tolerance factor (RTF) was originally identified in the placenta of mice and the isolated protein shown to have suppressive effects. In these studies, the gene cloned from thymus tissue was mapped to human chromosome 12. The role of recombinant RTF on cytokines was examined. In addition, we examined the human placenta by immunohistochemistry for RTF expression. RTF was expressed at the peripheral layer of cytotrophoblast in 7-9-week-old placentas. Using the RTF gene sequence, a recombinant protein was prepared and shown to induce IL-10 production. These data indicate that RTF is expressed by the tissues most intimately involved at the maternal-fetal interface, and its biological activity is capable of producing the necessary immune response for initiating and maintaining the maternal-fetal relationship.

Regeneration and tolerance factor's potential role in T-cell activation and apoptosis.

Regeneration and tolerance factor (RTF) is a novel membrane protein that has a diverse expression pattern and immunoregulatory properties. RTF is expressed in vivo on the surface of individuals with B cell chronic lymphocytic leukemia and on activated T lymphocytes of HIV infected individuals as determined by their coexpression with CD38 and HLA-DR. The unique expression patterns of this protein in vivo lead us to investigate its expression in vitro. The activation of human PBMCs through the TCR, using anti-CD3 antibody and PMA, upregulated cell surface expression of RTF from 2. 3% to 91.2% (mean channel fluorescence [MCF] increased threefold). The activation of Jurkat T cells through the TCR upregulated surface expression of RTF from 8.3% (MCF-1.3) to 58.7% (MCF-13.1). The Jurkat T-cell line was used as a model system to explore RTF's role in cellular activation. Using the Jurkat T-cell model, we found anti-RTF antibody induces apoptosis. The addition of anti-RTF antibody increased annexin V binding by threefold compared with the IgG1 kappa isotype control antibody (p < 0.00002) and activated caspase 3. These data indicate that RTF is expressed during T-cell activation and may be associated with apoptosis.

Expression of regeneration and tolerance factor correlates directly with human immunodeficiency virus infection and inversely with hepatitis C virus infection.

Hepatitis C virus (HCV) and human immunodeficiency virus (HIV) cause two of the most prevalent debilitating viral infections. HIV appears to induce a skewing toward a Th2 response, while in HCV infection a Th1 response appears to dominate. Regeneration and tolerance factor (RTF) may participate in driving or sustaining a Th2 cytokine response. The expression of RTF on CD3(+) T cells of HIV-seropositive (HIV(+)) individuals is increased. The purpose of this study was to compare the expression of RTF during HIV infections with that during HCV infections. Three-color flow-cytometric analysis of peripheral blood collected from HIV(+) HCV-seropositive (HCV(+)), HIV- and HCV-seropositive (HIV(+) HCV(+)), and HIV- and HCV-seronegative (HIV(-) HCV(-)) individuals was performed. Levels of RTF expression on T-lymphocyte subsets from these groups were compared, as were levels of RTF expression on activated T cells expressing CD38 and HLA-DR, to determine the relationship of RTF expression to these infections. We demonstrated that the expression of RTF on surfaces of T cells from HIV(+) individuals is upregulated and that its expression on T cells from HCV(+) individuals is downregulated. A twofold increase in the mean channel fluorescence of RTF on CD3(+) T cells was seen in both HIV(+) and HIV(+) HCV(+) individuals compared to HIV(-) HCV(-) individuals. HCV(+) individuals had lower levels of RTF expression than HIV(-) HCV(-) individuals (P < 0.005 for CD4(+); P < 0.0005 for CD8(+)). In terms of percentages of T cells expressing RTF, the groups were ranked as follows: HIV(+) > HIV(+) HCV(+) > HIV(-) HCV(-) > HCV(+). The results indicate that RTF expression correlates with HIV-associated immune activation and may be associated with Th2-type responses.

Regeneration and tolerance factor: a correlate of human immunodeficiency virus-associated T-cell activation.

Human immunodeficiency virus (HIV) infection causes extensive phenotypic alterations in lymphocytes. Cellular markers that are normally absent or expressed at low levels on quiescent cells are upregulated throughout the disease course. The transmembrane form of regeneration and tolerance factor (RTF) is expressed at negligible levels on resting T cells but is quickly upregulated following in vitro stimulation and activation. Recently, we reported that expression of RTF was significantly higher in cells from HIV-seropositive (HIV(+)) individuals than in cells from HIV-seronegative (HIV(-)) individuals. Because T cells from HIV(+) individuals express markers reflecting chronic activation, we hypothesized that these in vivo-activated cells would coexpress RTF. Flow cytometry was used to assess RTF expression on activated (CD38(+) and HLA-DR(+)) CD4(+) and CD8(+) T cells. HIV(+) individuals had higher percentages of RTF(+) CD38(+) (P < 0.0001) or RTF(+) HLA-DR(+) (P = 0.0001) CD4(+) T cells than HIV(-) individuals. In HIV(+) individuals, increased percentages of CD4(+) T cells that were RTF(+), RTF(+) CD38(+), and RTF(+) HLA-DR(+) correlated inversely with the absolute number and percentage of CD4(+) T cells and correlated positively with plasma beta(2)-microglobulin concentrations. HIV(+) individuals had higher percentages of CD8(+) T cells that were RTF(+) CD38(+) (P = 0.0001) or RTF(+) HLA-DR(+) (P = 0.0010). In HIV(+) individuals, increased percentages of CD8(+) T cells that were RTF(+) HLA-DR(+) correlated inversely with the percentage of CD4(+) T cells, and high percentages of CD8(+) T cells that were RTF(+) CD38(+) correlated positively with plasma beta(2)-microglobulin levels. These findings strongly suggest that increased RTF expression is a correlate of HIV-associated immune system activation.

Synthesis of acid-labile diplasmenyl lipids for drug and gene delivery applications.

The low pH environments characteristic of endosomal compartments and ischemic tissues provide an intrinsic pathway for triggering site-specific contents release from appropriately designed delivery vehicles. Accordingly, research in this group has focused on the design, synthesis and application of novel acid-sensitive lipids that will undergo facile lamellar (L alpha) to hexagonal (HII) phase transitions within these acidic sites. Previously, it has been demonstrated that plasmenylcholine-type lipids have excellent acid hydrolysis and contents release kinetics (Gerasimov et al., Biochim. Biophys. Acta. 1324 (1997) 200-214; Rui et al., J. Am. Chem. Soc. 120 (1998) 11213-11218). This paper describes the synthesis of three new acid sensitive lipids, based on a chiral 1,2-di-O-(1Z',9Z'-octadecadienyl)-sn-glycerol (6) platform, displaying phosphocholine (7), poly(ethyleneoxide) (8), and O-carbamoyl-N-diethylen-etriamine (10) headgroups. Intermediate 6 was obtained in 28% overall yield via a six step synthesis from (S)-(+)-2,2-dimethyl-1,2-dioxolane-4-methanol. Subsequent conversion to the final products was acheived in moderate (7 and 10) to excellent yields (8).

Expression of regeneration and tolerance factor on B cell chronic lymphocytic leukemias: a possible mechanism for escaping immune surveillance.

Regeneration and tolerance factor (RTF) is a protein expressed on developing tissue such as the thymus and the placenta. RTF has been reported to down-regulate cell-mediated immune responses. To examine the potential role of tumor-derived RTF to suppressing antitumor responses, we analyzed a panel of seven B cell tumor lines for the membrane RTF using a fluorescein isothiocyanate (FITC) conjugated monoclonal antibody, which reacts with membrane RTF. All the B cell tumor lines we examined express RTF on the cell surface. We also tested conditioned media from these B cell lines for their ability to suppress IL-2R expression on activated cells. Conditioned media from each B cell line suppressed IL-2R expression on activated Jurkat T cells and activated peripheral blood mononuclear cells. A monoclonal antibody to the biologically active portion of RTF reversed this suppressive activity. Finally, the tumor cell population from patients with chronic lymphocytic leukemia was found to express cell surface RTF. Thus, RTF expression could be a new mechanism used by tumor cells to escape immune surveillance.

Performance of three severely mentally retarded adults on vocational response chains during extinction.

The intrachain performance patterns of three severely retarded adults were analyzed under continuous reinforcement and extinction schedules. The three subjects performed a nine-step operant chain that required the placement of eight electrical components in a circuit board blank. The time to perform the entire chain and the time taken at each step of the chain were electronically monitored. A combined multiple-baseline, ABA reversal design was used. Reinforcers were delivered following completion of the chain during A phases and withheld during the B phase. Data indicated that overall chain performance was slower during extinction, and this effect was due primarily to reduced response speed on the early steps in the chain. Implications of these data for vocational habilitation of retarded adults were discussed.