Esterase expression by the different MTHC populations. The cell groups are the same as those shown in Fig 5. Red staining is indicative of α-naphthyl acetate esterase and blue is indicative of naphtol-AS-D-chloroacetate esterase, with methyl green as the counterstain. (a and d) Nonadherent and adherent parental MTHC cultured in murine GM-CSF, (b and e) nonadherent and adherent WTKit-expressing MTHC maintained in human SCF, and (c and f ) nonadherent and adherent V816Kit-expressing MTHC maintained without factor. The bar in (a) is equivalent to 38 μm and all photographs are at the same magnification.