Proliferation of single PB-derived CD34⁺IL-6R⁻ cells deposited in the wells of a 96-well flat-bottomed microtiter plate in the presence of the designated factors was serially analyzed on day 5 (left bar), day 10 (center bar), and day 14 (right bar) of culture. Each well was scanned under an inverted microscope. The number of cells per clone was directly counted in situ and wells containing greater than 8 cells were scored as positive clones. Large clones containing greater than 500 cells were picked up on day 14 and the number of cells was counted using a counting chamber. Shown are the clones of (□) 8 to 50, () 51 to 500, and (▨) greater than 500 cells.