CD45⁺ cells exposed to IL-3 acquire the ability to form vascular networks and to invade tumor in vitro. (A) For in vitro angiogenesis assay, CD45⁺ cells cultured in EBM-2 + IL-3 or EGM-2 were plated on Matrigel-coated surface. Histogram represents the number of tube-like structures per field. Data are the mean of 10 fields (± SD; *P < .05, EBM-2 + IL-3 vs EGM-2). Magnification, 10×. (B) Labeled CD45⁺ cells, cultured in EBM-2 + IL-3 or EGM-2, were incubated with tumor cells. After 48 hours, bright field (left panels) and fluorescent images (right panels) were taken using an inverted phase microscope. Magnification, 40×.