Functional features of immature CD56+ cell upon SCF+IL-2 stimulation. A, cytotoxicity of immature CD56+ cells (open squares) compared with IL-2 activated peripheral blood NK cells (closed circles). B. Cytotoxicity against P815 cells by immature CD56+ cells incubated with (open circles) or without 3G8 (open squares), compared with peripheral blood NK (closed symbols in the presence (closed triangles) or absence 3G8 (closed circles). This was a representative experiment of series of three. C Resting CD34+ cells (open squares) or IL-2 activated peripheral blood NK cells (open circles) were incubated at different ratio with K562. D. After 21 days stimulation with IL-2 and SCF, immature CD56+ cells were isolated from whole cells by electronic sorting and incubated in the absence (open squares) or presence (close squares) of K562. IL-2 activated peripheral blood NK cells were cultured in the absence (close circles) or presence (open circles) of K562 (representative of ten experiments). E. Inhibition of proliferation of the NK resistant cell line P815 by IL-2 activated peripheral blood NK cells (open circles) or with IL-2 activated peripheral blood NK cells (closed squares). Cells were then labeled with 3H-TdR and radioactivity (CPM) was measured by a β-counter (representative of three experiments).