Transient expression of thyroid hormone nuclear receptor TRbeta2 sets S opsin patterning during cone photoreceptor genesis.

Cone photoreceptors in the murine retina are patterned by dorsal repression and ventral activation of S opsin. TR beta 2, the nuclear thyroid hormone receptor beta isoform 2, regulates dorsal repression. To determine the molecular mechanism by which TR beta 2 acts, we compared the spatiotemporal expression of TR beta 2 and S opsin from embryonic day (E) 13 through adulthood in C57BL/6 retinae. TR beta 2 and S opsin are expressed in cone photoreceptors only. Both are transcribed by E13, and their levels increase with cone genesis. TR beta 2 is expressed uniformly, but transiently, across the retina. mRNA levels are maximal by E17 at completion of cone genesis and again minimal before P5. S opsin is also transcribed by E13, but only in ventral cones. Repression in dorsal cones is established by E17, consistent with the occurrence of patterning during cone cell genesis. The uniform expression of TR beta 2 suggests that repression of S opsin requires other dorsal-specific factors in addition to TR beta 2. The mechanism by which TR beta 2 functions was probed in transgenic animals with TR beta 2 ablated, TR beta 2 that is DNA binding defective, and TR beta 2 that is ligand binding defective. These studies show that TR beta 2 is necessary for dorsal repression, but not ventral activation of S opsin. TR beta 2 must bind DNA and the ligand T3 (thyroid hormone) to repress S opsin. Once repression is established, T3 no longer regulates dorsal S opsin repression in adult animals. The transient, embryonic action of TR beta 2 is consistent with a role (direct and/or indirect) in chromatin remodeling that leads to permanent gene silencing in terminally differentiated, dorsal cone photoreceptors.     

Inverted Vδ1/Vδ2 ratio within the T cell receptor (TCR)-γδ T cell population in peripheral blood of heart transplant recipients

We investigated the levels of TCR-γδ T cells and their subpopulations Vδ1 and Vδ2 in the peripheral blood lymphocytes (PBL) of 28 heart transplant (HTx) patients. Patients (n = 10) receiving cyclosporin A (CsA) for treatment of a nephrotic syndrome (NS) and 10 healthy individuals served as controls. There was no difference in levels of TCR-γδ T cells between the different groups. However, an elevated proportion of Vδ1⁺γδ T cells was found in the PBL of HTx patients, especially when these cells were present in their graft-infiltrating lymphocyte (GIL) cultures. Vδ1⁺γδ T cells of HTx patients showed normal expression of CD45RO and lacked the activation markers CD25 and HLA-DR. After expanding in IL-2-containing medium, PBL cultures of HTx patients more often were dominated by Vδ1 cells than PBL cultures of controls, in which Vδ2 cells were predominantly grown. The aberrant composition of the TCR-γδ population in HTx patients was not a result of immunosuppressive medication, since the proportion Vδ1⁺γδ T cells was normal in the PBL of the NS patients receiving a similar dose of CsA. It is postulated that long-term antigenic stimulation by the graft, at low level, might be responsible for the altered composition of the γδ pool in the HTx patients. Since no donor HLA-specific γδ T cells have been detected, other ligands, such as heat shock proteins, may be involved.     

丹参提取物对氧自由基引起的化学发光的抑制作用

观察了经调理的酵母多糖（ＯＺ）、Ｎ－ｆｏｒｍｙｌｍｅｔｈｉｏｎｙｌ－Ｌｅｕｃｙｌ－ｐｈｅｎｙｌａｌａｎｉｎｅ（ｆＭＬＰ）Ｃａｌｃｉｕｍ ｉｎｏｐｈｏｒｅ（Ａ２３１８７），等几种白细胞激动剂引起的大鼠腹腔中性粒细胞（ＰＭＮｓ）的化学发光和次黄嘌呤－黄嘌呤氧化酶系统（ＨＯ－ＸＯ）产生的化学发光。观察到了具有抗炎作用的中药单体７６４－３对ＰＭＮ吞噬ＯＺ引起的化学发光及ＨＯ－ＸＯ系统产生的化学发光具有明显     

Regulation of human basophil activation; the role of Na+ and Ca2+ in IL-3-induced potentiation of IgE-mediated histamine release from human basophils.

The release of mediators from human basophils is strongly enhanced by IL-3. However, the signalling pathways of IL-3 are poorly defined in these cells. Since external Ca2+ and Na+ play important regulating roles in histamine release, the possibility that these cations could be involved in the potentiation by IL-3 of the anti-IgE-induced histamine release from human basophils was considered, and it was observed that: (i) IL-3 dramatically decreased the external Ca2+ requirement for IgE-mediated histamine release. However, histamine release from IL-3-treated basophils became only partially independent of external Ca2+, since addition of EGTA in the external medium abolished the effect of IL-3; (ii) decreasing Na+ influx by lowering external Na+ concentration in isosmotic medium inhibited the potentiating effect of IL-3 on IgE-mediated release; (iii) amiloride, an inhibitor of Na+/Ca2+ and Na+/H+ exchanges, and its derivative, benzamil, more specific for Na+/Ca2+ exchanges, inhibited the release potentiated by IL-3. In contrast, the amiloride derivative 5-(N,N-dimethyl)-amiloride, more specific for Na+/H+ exchanges, slightly increased the IL-3-enhanced release. Thus, the decreased requirement for external Ca2+ and the dependence on external Na+, taken with the effect of the Na+/Ca2+ exchange inhibitors, suggest that Na+/Ca2+ exchanges are involved in the IL-3-induced enhancement of IgE-mediated human basophil histamine release.     

Production of a monoclonal antibody with specificity for deoxynivalenol, 3‐acetyldeoxynivalenol and 15‐acetyldeoxynivalenol

Monoclonal antibodies reactive with deoxynivalenol were generated following the immunization of mice with a deoxynivalenol‐mouse serum albumin conjugate. One of the anti‐deoxynivalenol monoclonal antibodies, designated C6–1, exhibited cross‐reactivity with 3‐acetyldeoxynivalenol and 15‐acetyldeoxynivalenol but not with nivalenol, T‐2 tetraol or scirpentriol. An indirect competitive ELISA based on this monoclonal antibody gave 50% inhibition values of 0–6 μg ml^‐1 for deoxynivalenol, 0–2 μg ml^‐1 for 15‐acetyldeoxynivalenol and 10 μg ml^‐1 for 3‐acetyldeoxynivalenol.     

ICAM-3, the third LFA-1 counterreceptor,is a co-stimulatory molecule for both resting and activated T lymphocytes

Optimal activation of human T cells mediated by ligation of CD3/T cell receptor (TcR) complex requires co-stimulatory signals. These can be provided by the adhesive interaction between receptor molecules on T cells and their counter-receptors on antigen-presenting cells. Soluble ICAM-3, anti-ICAM-3 and anti-CD3 mAb were utilized to address the role of the ICAM-3/LFA-1 pathway in TcR/CD3-dependent or -independent T cell activation. Immunoaffinity-purified ICAM-3 co-immobilized with suboptimal concentrations of anti-CD3 monoclonal antibody (mAb) stimulated T lymphocytes as monitored by the expression of the lymphocyte activation antigens CD25 and CD69. The mechanism underlaying this activation appear to involve the interaction of ICAM-3 with a β2 integrin, likely to be LFA-1, since mAb to the CD18 chain completely inhibited T cell activation. Similar experiments demonstrated that anti-ICAM-3 mAb were able to co-stimulate both resting (cord blood) and activated (T cell clones) T lymphocytes. On the contrary, anti-ICAM-1 mAb were only co-stimulatory for CD25 expression on activated but not on resting T cells. In addition, we have found that some γδ T cell clones bearing the Vδ1 segment were activated by direct mAb engagement of ICAM-3 in the absence of TcR/CD3 occupancy. Furthermore, immobilized anti-ICAM-3 mAb also induced development of dentritic processes. In conclusion, our data suggest that ICAM-3 on the surface of both T cells and antigen-presenting cells plays an essential role in the initiation of the immune response.     

Assessment of chemical carcinogen-induced transforming activity using BALB/c-3T3 cells

Summary The BALB/c-3T3 cell transformation assay evaluates the morphologic transforming potential of test chemicals using cultured mammalian cells as targets. The assay is semiquantitative and employs a contact-inhibited clone of cells derived from the original BALB/c-3T3 mouse cell line. Transforming activity, or a focus, is recognized as a dense layer of morphologically altered cells superimposed on a monolayer of the normal cell phenotype. The induction of transforming activity in a standard assay has been reported to correlate well with the carcinogenicity of many test chemicals in rodent bioassay; however, the standard assay does not detect carcinogens of all chemical classes. This report describes an operational protocol for the standard BALB/c-3T3 cell transformation assay. In addition, it provides assay acceptance criteria and a discussion of a method to evaluate transforming activity data.     

Down-regulation of LFA-1-mediated T cell adhesion induced by the HIV envelope glycoprotein gp160 requires phosphatidylinositol-3-kinase activity

Human immunodeficiency virus binds to CD4⁺ T lymphocyte by the interaction, in part, between its gp120 envelope glycoprotein and the CD4 molecule. We and others have reported that the lipid kinase phosphatidylinositol-3-kinase (PI3-kinase) is associated with the CD4-p56^lck complex and can be activated by various CD4 ligands. In a previous report we showed that the gp160 envelope down-regulates lymphocyte function-associated antigen-1 (LFA-1)-dependent adhesion between CD4⁺ T cells and B cells. This down-regulation was shown to be p56^lck-dependent. Here we investigate the role of PI3-kinase in the inhibition of adhesion induced by gp160 binding to CD4. We found that gp160 activates the PI3-kinase of HUT78 CD4⁺ T cell lines in a way dependent on CD4-p56^lck association, since no activation was detected when the interaction between CD4 and p56^lck was disrupted. It was also shown, using different inhibitors of the PI3-kinase (wortmannin, Ly294002 and antisense oligonucleotides), that this lipid kinase was necessary for the down-regulation of LFA-1-mediated adhesion induced by gp160. These results strongly suggest that PI3-kinase activation induced by gp160 leads to down-regulation of LFA-1-mediated T cell adhesion to B cells. Inhibition by gp160 of cytoskeleton rearrangement-dependent, anti-CD3-mediated T cell adhesion to B cells was blocked by neutralization of PI3-kinase activity, while inhibition of cytoskeleton rearrangement-independent, Mg²⁺-induced T cell adhesion was not. These results emphasize the role of PI3-kinase in the regulation of cytoskeleton structure. It is proposed that gp160 activates both p56^lck and PI3-kinase which lead to a cytoskeleton organization unfavorable for LFA-1 function.