Rapid expansion of allospecific cytotoxic T cell clones using nonspecific feeder cell lines without further addition of exogenous IL2.

The availability of large numbers of functionally defined cloned T cells would facilitate biochemical and molecular studies and might be a prerequisite for in vivo immunotherapy with cytotoxic lymphocytes. Exogenous interleukin-2 (IL-2) is generally considered to be the most important medium supplement for the growth of human T cells or cloned T cells. We have studied the role of particular feeder cells or stimulator cells, or both, on the expansion of a panel of cytotoxic and noncytotoxic human T cell clones. By using a combination of peripheral blood lymphocytes (PBL) and Epstein-Barr virus (EBV)-transformed B cell lines (B-LCL) as feeder cells in the presence of lectins, we were able to achieve continuous and rapid expansion of phenotypically different allospecific cytotoxic and noncytotoxic T cell clones even without (further) addition of exogenous IL-2. This culture system allows expansion of cloned cells for up to 60 generations within two months with full retention of cytolytic activity and the original target cell specificity, and without the obligatory addition of the original stimulator cell. It was found that, in principle, all combinations of EBV-transformed B cell lines (or even leukemia-derived B cell lines) and PBL feeder cells could serve the purpose, although some B cell lines gave better results than others. No evidence for HLA restriction between responder and feeder or between feeder cells was found, because cells could also be expanded with autologous feeder cells alone. The system appeared to be suitable for the expansion of various types of cytotoxic and non cytotoxic T cells, including cloned directed against major histocompatibility complex (MHC) class I or MHC class II antigens as well as MHC-nonrestricted activated killer (AK) clones.