Constitutive interleukin 2 production by the JURKAT human leukemic T cell line

Interleukin 2 (IL2) is a lymphokine produced from phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear cells and characterized biologically by its ability to maintain the in vitro proliferation of activated T cells. In a search for a convenient alternative source of biologically active human IL2, cells from the five established T cell lines, MOLT4, HSB2, CCRF-CEM, RPMI1301 and JURKAT were cultured at high concentrations for 18-36 h (induction cultures), and their cell-free supernatants thereafter screened on IL2-dependent cultured human and mouse T cells. MOLT4, HSB2, RPMI1301, and CCRF-CEM all failed to produce detectable levels of IL2. Of the three JURKAT cell lines obtained from different sources, one, designated JMN, produced high levels of IL2 activity. A second, JM, failed to produce any IL2, while the third, JHAN, produced intermediate levels. Stimulation of the IL2-producing JMN or JHAN variants with PHA, the phorbol diester 12-0-tetradecanoyl-phorbol-13-acetate (TPA), or both PHA and TPA together, resulted in an apparent increase of IL2 activity in the culture supernatant when assayed by a short-term tritiated thymidine incorporation test. However, both PHA and TPA added directly to the test cells caused substantial thymidine incorporation. Moreover, the nonproducer line JURKAT-JM could not be converted to an IL2 producer by stimulation with PHA, TPA, or both. When JMN supernatants were used to support actual long-term growth and cloning of T cells in limiting dilution, the constitutively produced IL2 was superior to that produced after PHA and/or TPA stimulation. Addition of TPA, but not of PHA, to lectin and TPA-free JMN IL2 resulted in a decreased ability of such supernatants to support clonal T cell growth, suggesting that TPA had a growth-inhibiting effect. These results show that the continuously growing JURKAT-JMN cell line could provide a suitable source of mitogen-free human IL2.