Cell surface marker expression. The histograms show the relative surface expression profiles of the indicated cell surface antigens by nonadherent parental MTHC cultured in murine GM-CSF, WTKit-expressing MTHC maintained in human SCF, and V816Kit-expressing MTHC maintained without factor. The negative control shown in each panel corresponds to parental MTHC labeled with the secondary antibody used in each case and is representative of background.