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Biomedical subjects

J J Tong

Publications and source records attributed to J J Tong.

5 recordsLinked to original sources
PubMed2001

Human gammadelta(+) T lymphocytes have in vitro graft vs leukemia activity in the absence of an allogeneic response.

Refractory acute lymphoblastic leukemia (ALL) is often incurable, and relapse rates following allogeneic bone marrow transplantation (BMT) remain high. We have reported that patients who develop increased numbers of gammadelta(+) T cells soon after BMT are significantly less likely to relapse. We now show in seven donor/recipient pairs that donor-derived Vdelta1(+)CD4(-)CD8(-)gammadelta(+) T cells are activated and proliferate in response to recipient primary ALL blasts. In addition, these cells have been shown to bind and lyse the recipient ALL blasts. Separately, gammadelta(+) T cells proliferate poorly or not at all in mixed lymphocyte culture against HLA-mismatched unrelated stimulator cells. These observations suggest that allogeneic gammadelta(+) T cells could be an effective immunotherapeutic strategy against refractory disease without the risk of graft-versus-host disease.

Cytotoxicity, Immunologic↗
PubMed1999

Co-ordinate expression of the pre-T-cell receptor complex and a novel immature thymocyte-specific antigen, IMT-1, during thymocyte development.

Previously we described a monoclonal antibody (mAb) that reacted with a cell-surface antigen, immature thymocyte antigen-1 (IMT-1), which is expressed on thymocytes of late CD4- CD8- (double negative) to early CD4+ CD8+ (double positive) differentiation stages. In this study, we investigated the expression of IMT-1 on various cell lineages in thymus as well as in peripheral lymphoid organs. We found that IMT-1 is expressed on T-cell receptor (TCR)-betalo and TCR-deltalo thymocytes, but not on TCR-betahi, TCR-deltahi or natural killer (NK)1.1+ thymocytes, or on peripheral alpha beta or gamma delta T cells. We also investigated the kinetics of expression of IMT-1 during fetal thymocyte development and compared it with the expression of the pre-TCR complex, comprising CD3, pre-TCR-alpha (pTalpha) and TCR-beta. We found that expression of both was similar, starting at day 14.5 of gestation, peaking on day 16.5 and gradually decreasing thereafter. Furthermore, the expression of both IMT-1 and pTalpha was drastically reduced when DN thymocytes in recombination activating gene (RAG)-2-/- mice were challenged in vivo with anti-CD3 mAb. These results indicate that IMT-1 is expressed on not only immature thymocytes of alpha beta T-cell lineage but also on those of gamma delta T-cell lineage, and that the expression of IMT-1 and the pre-TCR complex is co-ordinately regulated during the alpha beta lineage thymocyte development.

Animals↗
PubMed1998

Immature thymocyte antigen-1: a novel thymocyte marker discriminating pre- and post-selected thymocytes.

Previously, we described a mAb (1-23) reacting with a novel cell surface antigen expressed on thymocytes at late CD4-CD8- [(double negative (DN)] to early CD4+CD8+ [(double positive (DP)] differentiation stage. Since the expression of this molecule was restricted to immature thymocytes, we designated it as immature thymocyte antigen-1 (IMT-1). In this study, we have investigated the relevance of IMT-1 expression to thymocyte selection using TCR transgenic mice, scid mice or RAG-2-/- mice. The IMT-1+ population in DP thymocytes was decreased in the thymuses of MHC class I-restricted or class II-restricted TCR transgenic mice with a positively selecting MHC background when compared with that of the mice with a non-selecting MHC background. IMT-1+ DP thymocytes were also decreased in TCR transgenic mice in which negative selection occurs. When DP thymocytes in H-Y TCR transgenic mice were stimulated with CD3epsilon mAb in vitro as well as in vivo, the expression of IMT-1 on DP thymocytes was decreased. Furthermore, the expression of IMT-1 on DN thymocytes from RAG-2-/- mice was drastically reduced when CD3epsilon mAb was challenged in vivo. These results suggest that the expression of IMT-1 on DP or DN thymocytes is down-regulated by stimulation through TCR as well as pre-TCR. Taken together, these results show that IMT-1 is a unique surface marker which exquisitely separates pre-selected thymocytes from post-selected thymocytes.

Animals↗
PubMed1996

Wrist joint motion simulator.

A computer controlled wrist joint motion simulator has been developed that actively moves forearms from cadavers through cyclic planar flexion-extension motions, planar radial-ulnar deviation motions, and combined motions such as circumduction. Hybrid position-force feedback control algorithms are used to determine the wrist flexor and extensor tendon forces necessary to achieve the desired motions. The simulator was used in a series of 12 fresh cadaver forearms to produce both flexion-extension and radial-ulnar deviation motions and was found to cause repeatable, physiological movements. In these experiments, the extensor tendon forces were greater than those of the flexors, typically by a factor of two.

Biomechanical Phenomena↗
PubMedDate not supplied

A murine monoclonal antibody (928) recognizing a new epitope formed with a combination of HLA-DPA1*0201 and DPB1*0301 gene products.

A murine monoclonal antibody (mAb), 928, that recognizes a cell surface antigen (928 Ag) on a human Epstein-Barr virus-transformed fetal liver-derived lymphoid progenitor cell line (FL4.4) was generated. The 928 mAb reacted with only FL4.4; it did not react with any other 57 cell lines tested. Two color flowcytometry analysis of peripheral blood mononuclear cells (PBMC) revealed that the 928 mAb reacted with B cell and monocyte fractions from only two individuals out of 63 unrelated donors. Biochemical analyses showed that the 928 Ag composes of two molecules (33 and 34 Kd) and forms a SDS-resistant, noncovalently linked dimer conformation, the feature being similar to that of peptide-bound MHC class II molecules. Treatment of FL4.4 cells with the 928 mAb significantly facilitated homotypic cell aggregation. In addition, treatment of PBMC of the 928 Ag+ donor with recombinant IL-4 augmented the expression of the 928 Ag on CD64+ monocytes. Typing of HLA-DRB1, DPA1 and DPB1 alleles of the 928 Ag expressing and nonexpressing cells revealed that the 928 Ag is expressed only on PBMC of HLA-DPA1*0201 and DPB1*0301 positive donors. Finally, anti-DP antibody precleared 928 Ag from the cell lysate. These results demonstrate that the 928 mAb recognizes a polymorphic determinant of HLA-DPA1*0201-DPB1*0301 gene products. The possibility that amino acids in the groove of the peptide-binding site of HLA-DP molecules are critical for the 928 epitope is discussed.

Animals↗