Cpa3-Cre; Mcl-1fl/fl mice have markedly reduced numbers of mast cells. (A) Toluidine blue staining for mast cells in 4-μm-thick paraffin sections of glandular stomach wall (top) and dorsal skin (bottom) in Cpa3-Cre; Mcl-1+/+ mice (left) and Cpa3-Cre; Mcl-1fl/fl mice (right) shows a marked reduction in numbers of mast cells (purple) in mice in which Mcl-1 has been selectively deleted by Cpa3-Cre. Scale bar indicates 100 μm. (B-C) Numbers of mast cells in various tissues in Cpa3-Cre; Mcl-1+/+ (control) mice or Cpa3-Cre; Mcl-1fl/fl mice. Numbers of mast cells are shown as means + SEM per millimeter or per square millimeter of 4-μm-thick paraffin sections stained with 0.1% Toluidine blue (see “Methods”) in tissues from Cpa3-Cre; Mcl-1+/+ (n = 16) or Cpa3-Cre; Mcl-1fl/fl (n = 14) mice, except for mesentery window (n = 12 per group) and mammary stroma (n = 6 per group). (D) Percentage of mast cells in the live-cell population isolated from peritoneal lavage fluid from Cpa3-Cre; Mcl-1+/+ (control, n = 10) or Cpa3-Cre; Mcl-1fl/fl (n = 10) mice, analyzed by flow cytometry (FcϵRIα+; c-Kit+). Peritoneal mast cell numbers are shown as means + SEM. (B-D) **P < .01 and ***P < .001 versus corresponding values for Cpa3-Cre; Mcl-1+/+ mice. (E) Representative flow cytometry plots show comparable expression of FcϵRIα+ on peritoneal mast cells isolated from Cpa3-Cre; Mcl-1+/+ or Cpa3-Cre; Mcl-1fl/fl mice. In panels B-D, mice ranged from 3-10 months of age; mouse age did not influence mast cell numbers in each genotype (data not shown). Images were captured with an Olympus BX60 microscope with a 20× objective using a Retiga-2000R QImaging camera run by Image-Pro Plus Version 6.3 software (Media Cybernetics) and exported into Adobe Photoshop (CS3), in which images were white balanced and resized.
