SCF expression in the mouse skin. (A) Control study for PCR and restriction enzymes. Templates from human DJM-1 and mouse Pam212 keratinocytes were amplified after PCR and then digested with XmaI and NsiI. Human SCF products were cut to 137 and 425 bp and mouse SCF products to 257 and 305 bp. KC indicates keratinocytes. (B) Human mast cell development in NOG mouse skin was predominantly supported by mouse SCF. Expected 562-bp bands were observed after PCR reaction. The digestion patterns with XmaI and NsiI suggested the main source of SCF in the skin was mouse-derived SCF even after the xenotransplantation. 1 indicates NOG mouse not receiving transplant; 2, NOG mouse 12 weeks after xenotransplantation; 3, in vitro–derived cultured human mast cells from cord blood; and 4, negative control. The findings were similar when cDNA template from NOG mouse skin was used 8 weeks and 20 weeks after the transplantation. (C) Mouse SCF protein distribution in the NOG mouse skin. SCF localized in a physiologically cytoplasmic pattern in the epidermis. Magnification × 400.