Biochemical and biologic characterization of lymphocyte regulatory molecules. III. The isolation and phenotypic characterization of Interleukin-2 producing T cell lymphomas.

To isolate a stable tumor cell line source of Interleukin 2 (IL-2 formerly referred to as T cell growth factor), over 40 murine leukemia and lymphoma cells as well as 9 clonal helper and killer IL-2-driven T cell lines were screened for both constitutive and mitogen-stimulated IL-2 production. A radiation-induced splenic lymphoma from the B10.BR mouse, the LBRM-33 cell line, could be stimulated to produce over 1000 units/ml of IL-2 after 24 hr exposure to T cell mitogens. Peak IL-2 activity was found in supernatants harvested from 24-hr cultures of either 1% PHA or 20 micrograms/ml Con A-stimulated LBRM-33 cells (10(6) cells/ml). IL-2 production observed in both serum-free and serum-containing cultures represented between 1000 and 5000 times the quantity of IL-2 produced in conventional cultures of mitogen-activated rat or mouse spleen cells. Peak IL-2 production by LBRM-33 cultures (stimulated at either optimal Con A or PHA concentrations or co-stimulated with suboptimal amounts of mitogen and phorbol myristate acetate) was consistently accompanied by LBRM-33 cell death. Phenotypic characterization of the producer cell revealed LBRM-33 cells to be Thy 1+, Ly 1+, Ly 2+, Ly 3+, Qa 2-3+, Qa 3.2+, Qat 4+, and Ly 5+. These studies provide further evidence that IL-2 is a T cell product and establish a source of IL-2 that will be a valuable reagent for the isolation and further molecular characterization of this immunoregulatory molecule.