Sexual dimorphism in immunity: improving our understanding of vaccine immune responses in men.

Weaker immune responses are often observed in males compared to females. Since female hormones have proinflammatory properties and androgens have potent immunomodulatory effects, this sexual dimorphism in the immune response seems to be hormone dependent. Despite our current knowledge about the effect of sex hormones on immune cells, definition of the factors driving the sex differences in immunoclinical outcomes, such as the diminished response to infection and vaccination observed in men or the higher rates of autoimmunity observed in females, remains elusive. Recently, systems approaches to immune function have started to suggest a way toward establishing this connection. Such studies promise to improve our understanding of the mechanisms underlying the sexual dimorphism observed in the human immune system.