IL-3 induces differentiation of leukemic cells.

The initial morphology of the tumor cells (patient GUE) (A) (× 63) stained with May-Grünwald Giemsa was highly modified after 6-day culture with IL-3: The cells enlarged (B) (× 63) and, when activated during the last 48 hours with CD40L-transfected L cells, they acquired many fine dendrites (C) (× 63). Tumor cells die in culture medium alone (D) (× 10, as shown in phase contrast microscopy). Some dendrites can be seen in culture with IL-3 alone (E) (× 10) and on most of the cells that are either isolated or within clusters after CD40L activation (F) (× 10). CD83 (green fluorescence, red counterstaining) was not detected in fresh cells (G) (× 100) but became apparent after culture with IL-3, being localized in the cytoplasm (H) (× 100) and expressed at the cell surface after CD40L activation (I) (× 100).