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

Abstract 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 IL 2‐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.