INTERLEUKIN-2 ACTIVATION OF CHEMOTHERAPY AND GROWTH FACTOR-MOBILIZED PERIPHERAL-BLOOD STEM-CELLS FOR GENERATION OF CYTOTOXIC EFFECTORS

Based on our previous studies demonstrating marked anti-tumor activity of interleukin-2 (IL-2)-activated bone marrow in vitro and in vivo, w e studied the generation of anti-tumor cytotoxic effecters from chemot herapy- and growth factor-mobilized PBSC from 12 patients with differe nt solid tumors. As chemotherapy and growth factor priming could lead to important qualitative and quantitative alterations of lymphoid cell s, we also looked at the distribution of lymphoid cells contained in p rimed PBSC, In addition, different variables were defined for successf ul application of the technique to clinical protocols. The cells were placed in culture at varying cell densities in either serum-containing or serum-free culture medium, supplemented with IL-2, 100 or 1000 Cet us units/ml at 37 degrees C for 24 or 72 h, in flasks or in culture ba gs. Anti-tumor cytotoxicity was tested against A375 (melanoma), K562 ( CML) and Daudi (Burkitt's lymphoma) cell lines in standard 4h Cr-51 re lease assay, Marked cytotoxicity was seen against all cell lines teste d (A375: 32.7%+/-5.2; K562: 52.8%+/-4.8; Daudi: 50.5%+/-7.2), Cytotoxi city was comparable in serum-containing and serum-free culture conditi ons and in tissue culture flasks and bags, Cell density up to 10 x 10( 6)/ml was not associated with any significant decline in cytotoxicity, IL-2 activation of PBSC after thawing led to the generation of cytoto xicity comparable to that obtained with fresh PBSC, On flow cytometric analysis, the proportion of CD8(+) T cells and NK cells (CD56(+)) was found to be higher in primed PBSC than in control peripheral blood mo nonuclear cells. In addition a significant proportion of T cells was p ositive for activation markers such as CD25 and HLA DR and a further i ncrease was noted in the proportion of cells with these markers after IL-2 activation.