Reduced proliferative response in Hoxb4^-/- LSK cells. Enumeration of positive wells after 10-day single-cell assay (Lin^-Sca1⁺c-kit⁺) with SCF, FL, TPO, G-CSF, GM-CSF, and IL-3 in Terasaki plates. No significant difference was seen in the total number of positive wells (□). However, a significant reduction in wells positive for more than 50% of the well covered by cells (high proliferative clones, ▦) was seen in wells with Hoxb4^-/- cells (mean ± SD). Data are from 4 donors of each phenotype.