Biochemical and biologic characterization of lymphocyte regulatory molecules. VIII. Purification of interleukin 2 from a human T cell leukemia.

A cloned murine T cell line, LBRM-33 5A4, growing in culture can be activated by phytohemagglutinin (PHA) to secrete Interleukin 2 (IL-2) activity. In the absence of PHA, LBRM cells do not produce IL-2. The chemical and biologic properties of LBRM-derived IL-2 are compared to those of murine spleen-derived IL-2. The fractionation of culture supernatants from PHA-activated LBRM cells by ion-exchange chromatography, gel filtration, and isoelectric focusing (IEF) reveals that IL-2 activity is contained in a class of molecules indistinguishable in size (30,000) and charge (pI 4.3-4.7 and 4.9-5.1) from murine spleen IL-2. LBRM-derived IL-2 also exhibits the entire spectrum of biologic activities exhibited by spleen IL-2, stimulating the growth of established T cell lines in culture, the generation of cytotoxic T lymphocytes in thymocyte cultures and the induction of antibody responses in nude spleen cultures. Both LBRM and splenic-derived IL-2 activities exhibit similar properties after digestion with proteases, and various chemical and temperature treatments. Since IL-2 is derived from a cloned cell line, it is likely these lymphocyte assays are detecting a single class of molecules that act directly on activated T cells. The use of LBRM cells as a source of IL-2 should greatly facilitate studies on the molecular characterization and biologic activity of this class of lymphocyte regulatory molecules.