title: T-cell subsets mediate graft-versus-myeloid leukemia responses via different cytotoxic mechanisms.
abstract: Analysis of the cytotoxic effector mechanisms by which T-cell subsets mediate graft-versus-leukemia (GVL) activity is complicated by systems that use unfractionated T cells and leukemias that express alloantigens in addition to tumor-specific antigens. In this study, we used MMB1.10, a myeloid leukemia of C57Bl/6 (B6) origin, to examine the cytolytic pathways employed by syngeneic GVL-mediating, and therefore tumor antigen-specific, T-cell subsets. Wright-Giemsa staining and flow cytometric analysis indicated that MMB1.10 cells exhibited the morphology and markers most consistent with a monocytic-myeloid origin. Although reverse transcription-polymerase chain reaction analysis revealed that MMB1.10 cells expressed tumor necrosis factor (TNF) receptor types I and H, in vitro assays suggested that these cells were resistant to TNF-alpha-mediated cytotoxicity. For study of in vivo GVL responses, mice were challenged with MMBl.10 cells, lethally irradiated, and administered anti-Thy-1-treated (T-cell-depleted) bone marrow (ATBM) either alone or in combination with T-cell subsets from MMB1.10-presensitized mice. In regard to CD4+ donor T cells, 4 x 10(6) MMB1.10-presensitized wild-type (wt) cells exhibited increased GVL responses and survival values relative to tumor-challenged recipients of ATBM only. CD4 T cells from either perforin-deficient (pfp0) or Fas ligand (FasL)-deficient (gld) mice exhibited a lower level of GVL activity but did not produce any long-term survivors. Recipients of 5 x 10(6) wt B6 CD8+ T cells had significantly improved survival relative to tumor-challenged mice that received ATBM only. The same dose of gld CD8+ T cells exhibited a reduced but significant level of GVL activity, whereas cells from mice that were perforin-deficient or cytotoxicity doubly deficient (cdd) (ie, lacking perforin and FasL) exhibited no discernable GVL activity. Doubling the gld CD8+ T-cell dose to 10(7) cells resulted in further improved survival of recipients. We conclude that GVL effects mediated by CD4+ T cells can depend on either perforin- or FasL-mediated mechanisms, whereas the CD8+ T-cell subset is heavily dependent on perforin-mediated cytotoxicity.
authors.affiliation: Kimmel Cancer Institute, Jefferson Medical College, Philadelphia, Pennsylvania 19107, USA.
authors.forename: M H
authors.initials: MH
authors.lastname: Hsieh
authors.forename: A E
authors.initials: AE
authors.lastname: Patterson
authors.forename: R
authors.initials: R
authors.lastname: Korngold
mesh_terms: D000818:Animals; D016026:Bone Marrow Transplantation; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D003602:Cytotoxicity, Immunologic; D053222:Fas Ligand Protein; D016259:Genes, myc; D020544:Graft vs Leukemia Effect / Q000276:immunology*; D007951:Leukemia, Myeloid / Q000276:immunology* / Q000628:therapy; D008562:Membrane Glycoproteins / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D009368:Neoplasm Transplantation; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D014181:Transplantation Immunology; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology
chemical_list: D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D014409:Tumor Necrosis Factor-alpha; D054353:Perforin