Comparison of colony forming efficiencies of α6+/MHCI+ and α6+/MHCI- cells. A representative experiment of the colony forming efficiency (CFE) of sorted α6+/MHCI+ cells and α6+/MHCI- cells cultured on 3T3 fibroblast feeder layer. Primary culture of α6+/MHCI- cells exhibits lower CFE than α6+/MHCI+ cells. However, secondary culture of α6+/MHCI- cells exhibits higher CFE than α6+/MHCI+ cells (*P < 0.001). The CFE of α6+/MHCI+ cells increased ~3.6× from primary to secondary culture, while it increased ~38× for α6+/MHCI-. These results indicate higher proliferative potential of α6+/MHCI- cells compared to α6+/MHCI+ cells. Cells directly sorted by FACS (from niche, i.e. primary cultures) were seeded at the following concentrations: α6+/MHCI+ cells, 3,000 cells per plate; α6+/MHCI- cells, 10,000 cells per plate. It must be noted that even though higher cell number was plated for α6+/MHCI- cells in the primary cultures, the CFE of these cells was lower than the CFE of α6+/MHCI+ cells. In secondary cultures equal numbers of cells were plated (100 cells per plate) for both, α6+/MHCI+ cells, and α6+/MHCI- cells.