Adhesion to fibronectin after GM-CSF stimulation in mutant cell lines. Cells were incubated for 6 hours in the absence or in the presence of GM-CSF (10 ng/mL) and tested for adhesion to wells previously coated with fibronectin (10 μg/mL). The figure shows a photograph of the plate with each well stained for adherent cells with Wright-Giemsa stain.