Morphology and growth factor responses of KIL. (A) Phase-contrast microscopy of KIL at 37°C. Most KIL cells display the characteristic racket shape. Bar = 30 μm. (B) Survival of KIL in response to single cytokines. KIL cells were washed with phosphate-buffered saline and exposed to various cytokines (⬡, IL-7; ○, SCF; ×, Flt3L) at the indicated concentrations. Viable cells were counted after 4 days and expressed as percent of the maximal response. Each point represents the mean of triplicates. (C) SCF synergized with IL-7 to stimulate the proliferation of KIL. Each culture was started with 5 × 105 washed KIL cells. Cell numbers were determined on days 2, 4, and 6. ⬡ indicates IL-7 + SCF; ○, IL-7 only; and □, SCF only. Each point represents the mean of triplicates.
