Expression of mutant G-CSF-Rs in Ba/F3 cells. (A) Schematic representation of G-CSF-R proteins. Boxes 1 and 2 denote subdomains conserved in members of the hematopoietin receptor superfamily. Y, tyrosine; F, phenylalanine. (B) Flow cytometric analysis of G-CSF-R expression on parental Ba/F3 cells and Ba/F3 transfectants. Cells were either stained with biotinylated mouse anti-human G-CSF-R antibodies, followed by PE-conjugated streptavidin, biotinylated anti-streptavidin, and finally PE-conjugated streptavidin (unfilled), or without the anti–G-CSF-R step (filled).