Mature PLMCs can be isolated from human placental tissues. TEM imaging revealed that isolated placental MCs typically exhibited (A) an ovoid nucleus and an irregular outer cellular membrane characterized by microvilli, and (B) TEM image showing multiple immunoperoxidase-positive cytoplasmic granules indirectly stained using a mast cell tryptase-specific monoclonal antibody. (C) Laser scanning confocal microscopic imaging confirmed that isolated PLMCs cultured in the presence of SCF are positive for cell surface–expressed CD117 (PE in red) and mast cell tryptase (FITC in green).