Evolution of the mammary gland from the innate immune system?

The purpose of the mammary gland is to provide the newborn with coplous amounts of milk, a unique body fluid that has a dual role of nutrition and immunological protection. The results postulated that mammary glands evolved from the innate immune system as xanthine oxidoreductase evolved a dual role in the mammary gland and hence provide new evidence supporting the hypothesis that the nutritional function of the milk evolved subsequent to its protective function.