Sexual dimorphism in serum IFN-γ release following in vivo challenge with the iNKT cell ligand α-GalCer: contribution of ovarian hormones. Male and female mice received a single injection of α-GalCer and were killed 90 minutes later. Serum IFN-γ and IL-4 concentrations were determined by ELISA and expressed as means ± SEMs (6-10 mice per group from 3 separate experiments). In control mice that received an identical volume of vehicle solution alone, both cytokines were not detectable (< 20 pg/mL). (A) IFN-γ but not IL-4 serum release is higher in female (▪) than in male (□) adult mice; ^*P < .001. (B) Ovariectomy leads to decreased IFN-γ serum concentrations in females while orchidectomy is ineffective in males. Mice were gonadectomized (□) or sham-operated (▦) at 4 weeks of age, then challenged with α-GalCer at 8 weeks of age; ^**P < .01.