Figure 7. S4-3a has reduced capacity compared to wild-type SCF to elicit mast cell activation and related anaphylaxis in vivo.

(A–E) Analysis of systemic anaphylaxis after i.p. injection of 10 mg/kg SCF variants. (A–C) Movement of mice treated with the indicated agents. (A) Trajectory tracking of a representative mouse from each treatment. (B) Cumulative displacement and (C) total displacement over a one-minute period. (D and E) Body temperature of (D) control C57BL/6;Cpa3-Cre⁺; Mcl-1^+/+ or mast cell/basophil-deficient C57BL/6;Cpa3-Cre⁺; Mcl-1^fl/fl mice and (E) control C57BL/6;Mcpt8-Cre^+/−; DTA^−/− or basophil-deficient C57BL/6;Mcpt8-Cre^+/−; DTA^fl/− mice was measured at the indicated time points post-injection. (F–H) Assessment of local cutaneous anaphylaxis after injection of 25 μl PBS alone or 50 μg/ml SCF variants in the left and right ear pinna, respectively. (F) Difference in ear pinnae thickness of individual mice determined 2 h after injection compared to baseline values. (G) Images of mouse ears showing Evans blue extravasation of four representative mice treated with the indicated agents 3 h earlier. (H) Quantification of Evans blue dye in ear pinnae (such as those shown in G), calculated by subtracting respective values obtained from PBS-injected control ear pinnae of the same mouse. (A–H) Data represent the mean ± SEM and are pooled from two independent experiments (n≥5). *p<0.05, ***p<0.001, and ns = not significant (i.e., p>0.05) by unpaired, two-tailed Student’s t test. See also Figure S6.