Continuous culture of T cells cytotoxic for autologous human leukaemia cells

Abstract

CYTOTOXIC T lymphocytes (CTLs), capable of lysing autologous and HLA-identical human leukaemia cells, can be generated in vitro by culturing lymphocytes from patients in remission from leukaemia with X-ray irradiated autologous leukaemia cells and irradiated allogeneic normal cells in ‘three-cell’ mixed leukocyte culture (MLC) protocols^1–3. Additionally, T cells cultured with X-ray irradiated normal lymphocytes pooled from 20 unrelated individuals can differentiate into CTLs capable of lysing autologous Epstein-Barr (EB) virus-transformed lymphoblastoid cell lines and autologous human leukaemia cells, but not autologous normal cells^4,5. Because in vitro generated CTLs directed against syngeneic tumour cells can inhibit tumour development in some animal tumour systems^6–9, it is likely that if large numbers of human CTLs cytotoxic for autologous malignant cells could be generated in vitro, these CTLs could be effective in eliminating residual malignant cells in patients who have received chemotherapy. Recent findings that normal human T cells^10,11 and allosensitised mouse¹² and human CTLs^13,14 grow continuously in medium containing T-cell growth factor (TCGF) derived from super-natants of mitogen-stimulated lymphocytes, have raised the possibility that large numbers of in vitro generated CTLs cytotoxic for autologous human malignant cells could be propagated by growing CTLs in TCGF. We report here that in vitro generated CTLs cytotoxic for autologous lymphoblastoid cell lines (LCL) and human leukaemia cells can be increased in number by several millionfold by growth in TCGF and that the continuously growing CTLs are highly cytotoxic for autologous abnormal cells.