Hybrid cell contain blood progenitor cells as demonstrated by positive CFU growth.

*Colonies per 5000 cells/plate n = 2
Human blood cells are capable of forming colonies in medium containing human or mouse growth factors, while mouse blood cells are only capable of surviving in medium containing mouse growth factors. Hybrid cells (HLA+/H2Kd+) demonstrate growth characteristics of human blood progenitor cells. Cells from these CFUs were collected after 18 days in culture and stained for flow cytometry analysis with anti-H2Kd antibody. All cells that were originally H2Kd+/HLA+ at the beginning of the CFU culture lost the H2Kd antigen after the culture period indicating that the cells did not contain the H2Kd gene.