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X Y Ke

Publications and source records attributed to X Y Ke.

8 recordsLinked to original sources
PubMed1998

[Study on Trichosanthin induced apoptosis of leukemia K562 cells].

Trichosanthin (TCS), an eukaryotic ribosome-inactivating protein isolated from the root tuber of Trichosanthes plant, has various biological activities including abortion induction, antitumor, and anti-HIV. In this study, cultured human leukemia K562 cells treated with trichosanthin were examined. Analysis of the cells by single laser flow cytometry showed the sub-G1 peak. DNA extracted from these cells formed a characteristic "ladder" on agarose gel electrophoresis. Under electromicroscope, typical morphological changes of apoptosis were also observed. From all of these findings, we concluded that trichosanthin was able to induce apoptosis in K562 cells.

Antineoplastic Agents, Phytogenic↗
PubMed1997

Structure-function relationship of trichosanthin.

Trichosanthin (TCS), a 27 kDa ribosome inactivating protein extracted from the root tuber of Trichosanthes plant, was subjected to limited chymotrypsin digestion and three peptide fragments designated TCS-F1 72-247, TCS-F2 100-247, and TCS-F3 133-247 were generated. The RNA-N-glycosidase and cytotoxic activities of the TCS fragments were compared with that of inact TCS. TCS-F1 and TCS-F2 were biologically active, while TCS-F3 was completely inactive. Dose-dependent studies showed that TCS-F1 and TCS-F2 were less potent in their trophoblast cytotoxicity than intact TCS, however, full biological effect could still be obtained with a higher dosage. Based on the known three-dimensional structure of TCS, we postulate that the putative active site of TCS is located at amino acid residues 110 to 174.

Chymotrypsin↗
PubMed1996

Complete blockade of B7 family-mediated costimulation is necessary to induce human alloantigen-specific anergy: a method to ameliorate graft-versus-host disease and extend the donor pool.

Graft-versus-host disease (GVHD) is initiated by adoptively transferred donor T cells that recognize host alloantigens. Whereas the absence of donor T-cell proliferation to host alloantigens in a mixed-leukocyte reaction does not predict freedom from GVHD, the frequency of alloreactive precursor helper T lymphocytes (pHTL) is predictive. Complete blockade of 87 family-mediated costimulation, but not of major histocompatibility complex recognition or adhesion, induces host alloantigenic-specific energy by reducing cytokine production below threshold levels necessary for common gamma chain signaling. The associated reduction of alloreactive pHTL frequency below that predictive for GVHD, without depletion of either nonallospecific T cells or hematopoietic progenitors, has led us to embark upon human clinical trials of haplomismatched allogeneic bone marrow transplantation.

Abatacept↗
PubMed1995

B7-1 and B7-2 do not deliver identical costimulatory signals, since B7-2 but not B7-1 preferentially costimulates the initial production of IL-4.

The functional necessity for two CD28 counterreceptors (B7-1 and B7-2) is presently unknown. B7-1 and B7-2 equivalently costimulate IL-2 and interferon-gamma (IFN gamma) production and IL-2 receptor alpha and gamma chain expression. B7-2 induces significantly more IL-4 production than B7-1, with the greatest difference seen in naive T cells. Repetitive costimulation of CD4+ CD45RA+ T cells with B7-2 results in moderate levels of both IL-4 and IL-2, whereas repetitive costimulation with B7-1 results in high levels of IL-2 and low levels of IL-4. Therefore, B7-1 and B7-2 costimulation mediate distinct outcomes, since B7-2 provides an initial signal to induce naive T cells to become IL-4 producers, thereby directing the immune response more towards Th0/Th2, whereas B7-1 is a more neutral differentiative signal.

3T3 Cells↗
PubMed1995

Induction of the transcription factors NF-kappa B, AP-1 and NF-AT during B cell stimulation through the CD40 receptor.

To address elements that might uniquely characterize CD40 mediated signaling, the nuclear expression of three transcription factors was evaluated following B cell stimulation by CD40L and by anti-Ig antibody. Cross-linked CD40L was found to induce nuclear expression of NF-kappa B, AP-1 and NF-AT with a time course and intensity similar to that produced by anti-Ig. Examination of NF-kappa B in more detail demonstrated that the CD40 mediated expression of DNA binding complexes correlated with induction of trans-activating activity which again attained similar levels following cross-linking of CD40 and slg. Despite the marked similarity in transcription factor induction triggered through CD40 and slg, differences in the intracellular signaling pathways utilized were apparent in that protein kinase C (PKC) depletion did not affect CD40 mediated induction of NF-kappa B even as induction by anti-Ig was abolished. These results suggest that a 'final common pathway' or convergence of transcription factor induction may exist for two distinct receptors, each of which is individually capable of triggering cell cycle progression, despite the use of separate intracellular signaling pathways that differ at the level of PKC. Although transcription factor induction was similar for CD40L and anti-Ig early on, subtle differences in expressed NF-kappa B and AP-1 nucleoprotein complexes were apparent at 24 h. Such differences may play a role in determining the variant effects on B cells of stimulation through these two receptors.

Animals↗