Monocytes were needed early in the ex vivo cultures to initiate the spontaneous proliferation of purified leukemic cells. (A) Six-day spontaneous proliferation of purified leukemic cells, monocytes, and mixtures of purified leukemic cells and monocytes (leukemic cells:monocytes = 1:1). 3H-thymidine was added to the cultures during the last 6 hours of culture. Anti–IL-2 or the control antibody, UPC10, was added to the cultures at day 0. Cells were harvested and analyzed for 3H incorporation. (B) Four-day spontaneous proliferation of purified leukemic cells from 2-day PBMC cultures. Anti–IL-2 and control antibody UPC10 were added at the beginning of the culture. 3H-thymidine was added during the last 6 hours of culture. The data are representative of data from 4 different patients.
