ZKS cells stimulate differentiation of zebrafish hematopoietic precursors; morphologic evidence. (A) Representative hematopoietic cells recovered from purified βactin:GFP⁺ lymphoid (top) and precursor (bottom) fractions cultured on ZKS cells stained with May-Grünwald/Giemsa. All images were photographed at 1000×. After photographing, cells were cut and pasted from multiple fields to create composite image. (B) Percentages of lineages derived from lymphoid fraction (left) and precursor fraction (right) recovered cell populations over 8 days of culture. Percent population listed at left, days in culture on ZKS stroma at bottom. Blue indicates lymphoid; purple, precursor; and green, myeloid.