Autoimmune diseases strike women three times more than men

With the disease lupus, nine times as many women are affected as men. In fact, women are at a greater risk of suffering from asthma and allergies as well as autoimmune disorders such as Crohn's disease and rheumatoid arthritis. Does this have anything to do with the fact that boys are more likely to spend time playing outdoors than girls and so get more exposure to germs?