Biomedical subjects

X Sheng-Tanner

Publications and source records attributed to X Sheng-Tanner.

6 recordsLinked to original sources

PubMed2000

Characterization of graft-versus-host disease in SCID mice and prevention by physicochemical stressors.

BACKGROUND: Graft versus host disease (GVHD) prevents potentially curative allogeneic stem cell transplantation from being offered to cancer patients who lack a suitably matched donor. New methods to prevent GVHD are required to allow successful transplants across major histocompatibility complex barriers. METHODS: A model of GVHD in C.B-17 SCID mice was developed to allow the study of allo-activated donor T cells without confounding effects of host lymphocytes. The abilities of cyclosporin-A, anticytokine antibodies, and oxidative stress to prevent GVHD in this model was studied. RESULTS: T cells from major histocompatibility-mismatched donor mice caused severe GVHD in sublethally irradiated SCID hosts that could be ameliorated by coadministration of donor bone marrow but not by cyclosporine-A or anticytokine antibodies. In contrast, three-log more T cells could be injected without clinical consequences if they had been pretreated with a combination of heat, ultraviolet light, and oxygenation. The effect was not the trivial result of donor T cell destruction because T cell reconstitution, although delayed, recovered to normal levels within 2 weeks. Protection from GVHD required oxygenation and was associated with normalization of the CD4/CD8 donor T cell ratio, recovery of host hematopoiesis, and decreased inflammatory cytokine production. CONCLUSION: Pretreatment of donor T cells with a combination of physicochemical stressors effectively prevents GVHD caused by major major histocompatibility disparities and may facilitate the safe transplantation of patients without HLA-identical donors.

Animals↗

PubMed1999

Long-term persistence of IL-2-unresponsive allogeneic T cells in sublethally irradiated SCID mice.

Donor T cells that are activated by host alloantigens initiate graft versus host disease (GVHD) but their long-term fate is poorly understood. The behavior of alloreactive donor T cells was studied in sublethally irradiated SCID mice. Intravenous injection of 10(6) allogeneic lymphocytes caused a severe form of GVHD, characterized by host hematopoietic atrophy. Fifty-fold fewer donor cells did not induce disease and were not simply rejected by radioresistant host mechanisms. Instead, low numbers of allogeneic T cells expanded 20- to 50-fold and remained for >1 year without causing evidence of GVHD. Persistent non-cycling donor cells with an activated phenotype were mainly found in the spleen. Tolerance was inferred by the recovery of host hematopoiesis, despite the presence of donor allogeneic T cells, and the inability of long-term persisting donor T cells to mediate cellular cytotoxicity or proliferate in response to exogenous IL-2 or antigenic stimulation in vitro. The TCR density of long-term persisting donor T cells was down-regulated. These findings suggest that the development of GVHD depends on the magnitude of the initial anti-host response. Subsequently donor cells differentiate, over several months, into a senescent-like state. This behavior questions the rationale for current treatment approaches to GVHD and is of relevance to any clinical situation where chronic T cell activation takes place in the absence of thymic development.

Animals↗

PubMed1998

Permeabilization and fixation conditions for intracellular flow cytometric detection of the T-cell receptor zeta chain and other intracellular proteins in lymphocyte subpopulations.

Expression of the T-cell receptor (TCR) zeta chain in normal individuals was studied by two-color flow cytometric analysis using digitonin-permeabilized human peripheral blood lymphocytes. Optimal detection of the TCR zeta chain involved fixation of cells in 0.25% paraformaldehyde for 2 min and permeabilization with 500 microg/ml of digitonin at 4 degrees C. Permeabilized lymphocytes and monocytes displayed decreased forward light scatter properties. Neutrophils did not survive this permeabilization/fixation/washing procedure. Permeabilization did not affect the ability of antibodies to CD3, CD4, CD8, CD16, and CD19 to detect CD antigens on lymphocytes, and the percentage of lymphocytes reacting with these antibodies was comparable between untreated and permeabilized cells. Staining of the TCR zeta chain was accomplished by incubating permeabilized cells with unconjugated antibody to the zeta chain, followed by an FITC-conjugated F(ab')2 goat anti-IgG. Following TCR zeta chain staining, cells were blocked with 25 microg/ml of mouse IgG for 20 min to saturate the goat anti-mouse antibody and then incubated with a phycoerythrin-conjugated mouse antibody to a variety of lymphocyte surface antigens. The TCR zeta chain was observed in lymphocytes displaying CD3, CD4, CD8, CD16, or TCRgammadelta markers. This permeabilization/fixation/washing procedure was also validated for detection of another intracellular T-cell protein known as the cytolytic granule-associated protein, recognized by the TIA-1 antibody. Thus the technique can be applied to detection of at least two different intracellular T-cell markers.

Antibodies, Monoclonal↗

PubMed1998

An oxidative stress-mediated death pathway in irradiated human leukemia cells mapped using multilaser flow cytometry.

OCI/AML-2 acute myeloid leukemia cells were found to undergo apoptosis after treatment with y rays from a 137Cs source. Multilaser flow cytometry techniques using probes for live cell function were used to monitor the biochemical changes that occurred prior to the loss of surface membrane integrity. These showed increases in the generation of reactive oxygen species (ROS) and in the glutathione (GSH) content of irradiated cells. An additional population of cells that showed a further increase in ROS and depletion of GSH was seen in irradiated cells but not in controls. This population showed loss of mitochondrial membrane potential (deltapsim), indicative of the mitochondrial permeability transition, and exposure of phosphatidylserine on the cell surface. Increases in intracellular calcium were observed in a proportion of these low-deltapsi(m)/high-ROS cells. Similar findings were seen using the antileukemia drug cytosine arabinoside (ara-C), although cell cycle analysis showed that the loss of deltapsi(m) occurred mainly in G1 phase with ara-C treatment, and mainly in G2 phase with irradiation. Furthermore, the protective effect of overexpression of BCL2 was more pronounced after ara-C treatment than with radiation. Cells of the TP53 (formerly known as p53)-null human AML line OCI M2 showed growth arrest in G2 phase after radiation treatment, with no loss of deltapsi(m) or morphological changes indicative of apoptosis. The flavine-dependent oxidoreductase inhibitor diphenylene iodonium failed to inhibit generation of ROS in irradiated OCI/AML-2 cells, indicating that the mechanism is unlikely to involve the TP53-induced gene PIG3. These results show that oxidative stress can occur in irradiated human leukemia "blasts", and may play a direct role in radiation-induced apoptosis.

Antimetabolites, Antineoplastic↗

PubMed1992

Correlation between lymphocyte-induced donor-specific tolerance and donor cell recirculation.

Intravenous infusion of mice with major histocompatibility complex (MHC) incompatible lymphocytes can inhibit the response of recipient T cells capable of recognizing the injected cells, and can enhance survival of grafts sharing MHC with the injected cells. However, neither T cell inactivation nor graft survival enhancement is always achieved. This is particularly true for donor cells that are fully allogeneic (as compared to semiallogeneic) to the recipient. We show here that both donor-specific induced response reduction and graft survival enhancement are directly correlated with the ability of the injected lymphoid cells to persist in the recirculating lymphocyte pool of the host. Whether donor cells persist correlates inversely with the level of natural killer cell (NK) activity in the host. Fully allogeneic cells can only persist in hosts with low NK activity and can then induce response reduction. Both persistence and response reduction are abrogated by injection of the host with poly-I:C, a treatment that boosts host NK activity. The same treatment also destroys the ability of semiallogeneic injected cells to persist, to induce response reduction, and to enhance skin graft survival.

Animals↗

PubMed1992

Rapid and long-term changes to host cytotoxic T lymphocyte precursors reactive to donor antigens caused by intravenous injection of histoincompatible lymphocytes.

It has been shown previously that a single intravenous injection of mouse F1 LNC into either parent results in a rapid reduction in the ability of the recipient to generate CTL reactive against donor antigens in an in vitro MLR. The underlying mechanism appears to be the inactivation of host CTL precursors that can recognize donor lymphocytes that have entered the recirculating pool. The donor lymphocytes may be acting as functionally deleting APC, or veto cells. Here, we have injected C57BL/6 (B6) mice with (C57BL/6 x DBA/2) F1 (F1) LNC. The CTL response against donor LNC was maximally reduced by 2 days and stayed reduced for at least 6 weeks, but ultimately recovered to normal levels. The response reduction mechanism remained operative during the period when the response was reduced: Fresh FITC-labeled B6 LNC introduced into B6 recipients of an earlier injection of F1 LNC were as effectively deleted of F1-reactive CTLp as the original host B6 LNC population, the fresh FITC-labelled B6 LNC being separated from host B6 LNC by cell sorting before testing. When B6 mice injected with F1 LNC ultimately recovered their response against F1 donor antigens, reinjection of F1 LNC did not induce a new response reduction. Instead of entering the recirculating pool, the injected F1 cells were rapidly removed by a specific immune process.

Animals↗