title: Lethal graft-vs-host disease across major histocompatibility barriers: requirement for leucyl-leucine methyl ester sensitive cytotoxic T cells.
abstract: L-leucyl-L-leucine methyl ester (Leu-Leu-OMe) is selectively toxic for human natural killer (NK) cells and cytotoxic T lymphocytes (CTL) at both the precursor and effector stage of differentiation. The present studies explored the effects of Leu-Leu-OMe on murine spleen cell function. Leu-Leu-OMe exposure removed NK function from murine spleen cells but spared their capacity to proliferate in response to lipopolysaccharide and Con A. The capacity to generate CTL from both L3T4 (+) and Lyt-2 (+) precursors was lost after Leu-Leu-OMe treatment, whereas alloantigen-induced proliferation and interleukin 2 (IL 2) production by L3T4 (+) T helper cells remained intact. Lethal graft vs host disease (GVHD), which developed in irradiated (C57BL/6 X DBA/2)F1 recipients of C57BL/6 bone marrow and spleen cells was completely prevented by Leu-Leu-OMe treatment of donor cells. In contrast depletion of Lyt-2 positive cells from the donor inoculum did not prevent acute GVHD in this fully major histo-compatibility complex (MHC) incompatible strain combination. However, Leu-Leu-OMe treatment of the Lyt-2 depleted inoculum completely prevented lethal GVHD, although the treated cells retained the capacity to proliferate and secrete IL 2 normally after in vitro stimulation with (C57BL/6 X DFA/2)F1 spleen cells. These findings indicate that L3T4 (+) T helper cells alone are unable to initiate lethal GVHD in this H-2 incompatible strain combination. Rather, lethal GVHD requires the transfer of a Leu-Leu-OMe sensitive T cell subset, likely to be thymus educated pre-CTL. Leu-Leu-OMe treatment should provide a useful way to delineate subpopulations of cells involved in the production of lethal GVHD and an approach to preventing this complication of bone marrow transplantation.
mesh_terms: D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte; D000950:Antigens, Ly / Q000032:analysis; D000954:Antigens, Surface / Q000032:analysis; D016026:Bone Marrow Transplantation; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D004151:Dipeptides / Q000494:pharmacology*; D006086:Graft vs Host Disease / Q000276:immunology*; D006183:H-2 Antigens / Q000032:analysis; D007376:Interleukin-2 / Q000096:biosynthesis; D007694:Killer Cells, Natural / Q000276:immunology; D008213:Lymphocyte Activation / Q000187:drug effects; D008285:Major Histocompatibility Complex; D051379:Mice; D013601:T-Lymphocytes / Q000145:classification / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects / Q000276:immunology*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology
chemical_list: D000945:Antigens, Differentiation, T-Lymphocyte; D000950:Antigens, Ly; D000954:Antigens, Surface; D004151:Dipeptides; D006183:H-2 Antigens; D007376:Interleukin-2; C045139:leucyl-leucine-methyl ester