Specific adoptive therapy of established leukemia with syngeneic lymphocytes sequentially immunized in vivo and in vitro and nonspecifically expanded by culture with Interleukin 2.

Abstract The aim of the current study was to determine whether lymphocytes from mice immunized in vivo to antigenic syngeneic tumors could be rendered more effective in adoptive therapy of advanced disseminated leukemia by specific activation in vitro followed by proliferation induced by a nonspecific stimulus. Spleen cells from C57BL/6 mice immunized in vivo with either of 2 noncross-reactive syngeneic tumors, a Friend virus-induced leukemia, FBL-3, and a chemically induced virus-negative leukemia, EL-4(G−), were specifically activated by culture for 7 days with the immunizing tumor. Activation of cytotoxic lymphocytes was documented by a 4-hr chromium release assay (CRA). After in vitro activation, lymphocytes were induced to proliferate in vitro tor 12 days by repeated addition of supernatants from Con A-stimulated lymphocytes containing Interleukin 2 (T cell growth factor). After 7 days in culture, only 17% of cells remained viable. However, Interleukin 2-induced proliferation from day 7 to day 19 resulted in a greater than 7-fold expansion in cell number. When tested in vitro in the CRA, such expanded cells maintained their specific cytolytic reactivity. When tested in vivo in tumor therapy as an adjunct to chemotherapy (adoptive chemoimmunotherapy), they were effective specifically against the immunizing tumor. On a cell-per-cell basis, cells sequentially immunized in vivo and in vitro and numerically expanded by culture with Interleukin 2 were significantly more effective in prolonging the median survival time of tumor-bearing mice than were cells immunized in vivo and tested without culture. However, cultured ceils were no more effective in curing mice.