Fig. 1

PSA-induced anaphylaxis and serum histamine levels in female and male C57BL/6 mice. a Both male and female mice showed a decrease in body temperature after injection with IgE anti-DNP antibody (10 μg/mouse, i.p.), followed 24 h later with vehicle (PBS i.p., n = 4/sex) or DNP-HSA (500 μg/mouse, i.p., n = 8/sex). Female mice exhibited a trend (p < 0.06); Two-way ANOVA on repeated measures) (p < 0.05 with individual t-tests at each time point) of lower body temperature than male mice after anaphylaxis challenge along with females demonstrating more severe peak temperature drop (b). c Over the 120-min PSA challenge, females exhibited a trend of increased clinical scores of anaphylaxis, compared to males, a difference that was statistically significant around the peak of symptoms at 60 min. d Serum levels of histamine, as measured by ELISA 30 min after DNP (values represent results from one individual experiment with n = 4 animals/sex; results were replicated in three independent experiments) showed that both male and female mice had an increase in histamine, and the increase was greater for females. e Representative photomicrographs of intestinal mesentery from male and female mice stained with toluidine blue showing increased degranulation in DNP-treated animals; original magnification, ×100, bar = 20 μM. f The number of mast cells was similar in female and male mice. Mast cells were counted in five randomly chosen fields per mouse. Values represent mean ± SE. †P < 0.10, *P < 0.05, ^# P < 0.0001