Aim: Ral-binding protein 1 (RLIP76) is a cell surface protein that catalyzes the extrusion from the cell of reduced glutathione (GSH) conjugates. We recently demonstrated the presence of serum antibodies to RLIP76 (aaRLIP76) in patients with immune-mediated diseases characterized by vascular dysfunction. The aim of this work was to analyze the possible implication of gender in this issue, investigating the effects of aaRLIP76 in rat vascular smooth muscle cells and human endothelial cells from males and females. Results: We observed that, after aaRLIP76 treatment, vascular cells from females showed a significantly higher susceptibility to the disturbance of intracellular redox balance, in terms of H(2)O(2) and O(2)(center dot) production, 4-hydroxy-t-2,3-nonenal and GSH levels, C-Jun NH2 kinase signaling activation, and apoptosis in comparison with cells from males. Interestingly, under mild oxidative stress (H(2)O(2) 30 mu m for 30 min), these sex-associated differences became significantly more pronounced. Experiments carried out in the presence of sex hormones in the culture medium clearly suggested that estrogens could significantly increase the susceptibility of cells from females to the effects of aaRLIP76, whereas cells from males appeared unaffected. Innovation: These results open a new perspective in the gender-dependent pathogenic mechanisms of autoimmune diseases characterized by vascular dysfunction. Conclusions: Altogether these results suggest that the impairment of RLIP76 by aaRLIP76 can play a role in the damage of vascular cells from females, contributing to the gender-associated pathogenesis of immune-mediated vascular diseases. Antioxid. Redox Signal. 15, 2825-2836.