Phorbol myristate acetate-stimulated production of interleukin 2 by T-cell lymphoma and constitutive production by derived hybridomas

Abstract

To isolate a stable tumor cell line source of IL-2 (TCGF), 19 murine T-cell lines and their derivatives were screened for both constitutive and mitogen-stimulated IL-2 production. The cloned subline of a mouse thymic lymphoma EL-4 designated as EL-4TF could be stimulated with PMA to produce 80 U/ml of IL-2. A TK- EL-4TFR mutant line has been selected from the EL-4TF cell population by treatment with 5-BrdUrd. The EL-4-TFR cells were stimulated with PMA and fused with the cells of thymic lymphoma BW5147. The resulting BH3 hybrid cell population was repeatedly cloned and tested for constitutive IL-2 production: two of the BH3 hybridoma clones were found to produce IL-2 constitutively. The IL-2 of EL-4TF origin was found to support permanent in vitro growth of IL-2 dependent, tumor-specific T killer cell line CTLL when present in culture medium at a concentration of at least 0.1 U/ml. Since the EL-4TF-derived IL-2 preparations were contaminated with PMA, it was of interest whether PMA alone has a growth-promoting activity in CTLL cell cultures. Permanent cultivation of CTLL cells in an IL-2-free medium containing PMA was not possible. However, both mitogenic and co-mitogenic effects of PMA on CTLL cells were observed.