Enumeration of mast cells in vivo in lethally irradiated mice reconstituted with wild-type, Apaf-1^-/-, or caspase-9^-/- fetal liver cells. (A,D) The proportion of mast cells (as percent of nucleated cells) in the peritoneal lavage was determined by immunofluorescent staining with antibodies to c-kit and Ly5.2 (donor cell specific) (A) or in cytospins by their deep blue staining with May Grunwald/Giemsa (D). In panel D, ♦ indicates individual mice; horizontal bars, the mean percentage for each genotype (n = 6, wild type; n = 5, Apaf-1^-/-; n = 3, caspase-9^-/-). (B,C) The frequency of mast cells in the skin of reconstituted animals was determined by counting the number of toluidine blue-staining cells in 2-cm lengths of sectioned skin. ♦ indicates individual mice; horizontal bars, the mean percentage for each genotype (n = 7, wild-type; n = 8, Apaf-1^-/-;n = 4, caspase-9^-/-).