Study shows how female immune cells keep their second X chromosome shut off
(PHYSorg.com Biology)

Autoimmune diseases tend to strike women more than men and having multiple X chromosomes could be the main reason why. While a process called X chromosome inactivation serves to balance out gene dosage between males and females, some genes on the `inactive X` chromosome in immune cells can sometimes escape this process, giving women an extra dose of immunity-related gene expression.