Expansion of cytolytic CD8(+) natural killer T cells with limited capacityfor graft-versus-host disease induction due to interferon gamma production

T cells with natural killer cell phenotype and function (NKT cells) have be en described In both human and murine tissues. In this study, culture condi tions were developed that resulted in the expansion of CD8(+) NKT cells fro m bone marrow, thymus, and spleen by the timed addition of interferon-gamma (IFN-gamma), interleukin 2 (IL-2), and anti-CD3 monoclonal antibody. After 14 to 21 days In culture, dramatic expansion of CD3(+), CD8(+), alpha beta T-cell receptor(+) T cells resulted with approximately 20% to 50% of the ce lls also expressing the NK markers NK1.1 and DX5. The CD8(+) NKT cells demo nstrated lytic activity against several tumor target cells with more than 9 0% lysis by day 14 to day 21 of culture. Cytotoxicity was observed against both syngeneic and allogeneic tumor cell targets with the greatest lytic ac tivity by the cells expressing either NK1.1 or DX5. The expanded CD8(+) NKT cells produce T(H)1-type cytokines with high levels of IFN-gamma and tumor necrosis factor oz. Expansion of the CD8(+) NKT cells was independent of C D1d. Ly49 molecules were expressed on only a minority of cells. A single in jection of expanded CD8(+) NKT cells was capable of protecting syngeneic an imals from an otherwise lethal dose of Bcl1 leukemia cells. Expanded CD8(+) NKT cells produced far less graft-versus-host disease (GVHD) than splenocy tes across major histocompatibility barriers, even when 10 times the number of CD8(+) NKT cells as compared to splenocytes were injected. This reducti on in GVHD was related to IFN-gamma production since cells expanded from IF N-gamma knock-out animals caused acute lethal GVHD, whereas cells expanded from animals defective in fas ligand, fas, IL-2, and perforin did not. Thes e data indicate that CD8+ NKT cells expanded in this fashion could be usefu l for preserving graft-versus-leukemia activity without causing GVHD. (Bloo d. 2001;97:2923-2931) (C) 2001 by The American Society of Hematology.