A Bovine Mammary Endothelial/Epithelial Cell Culture Model of the Blood/Milk Barrier

The circulatory system is the body’s inter-organ highway for transporting nutrients to the various organs and removing waste products. It also delivers cellular and soluble defense mechanisms to protect the body against invading pathogens. The circulatory system is complex but well defined and relatively easy to study. However, the movement of nutrients and humoral and cellular defense mechanisms from blood to the various organs of the body is much more complex and difficult to study. Each organ has specific requirements that must be satisfied by the blood. Study of the mechanism(s) for satisfying these requirements from blood requires a close look at the cells lining the blood vessels (endothelium) and the specific organ tissues. In studies of the mucosal organs, epithelial cells transport or synthesize and secrete organ-specific products, i.e., mammary gland, milk and colostrum; lungs, absorb O₂ and expel CO₂ ; gut, digestive enzymes, mucous, and antibodies. Epithelial cells also serve as the first line of defense against the onslaught of bacteria, viruses, parasites, chemicals, and other biological hazards.