Peyer's patches are a collection of large oval lymph tissues that are located in the mucus secreting lining of the small intestine. These lymph nodules are especially abundant in the lowest portion of the small intestine that empties into the larger intestinal tract, an area of the digestive system referred to as the ileum. The lymph system and associated tissues and structures present a strong line of defense against invading bacteria, parasitic microbes, viruses, and other foreign particles such as cancer cells. The lymph structures termed peyer's patches contain high concentrations of white blood cells (termed lympocytes) that help protect the body from infection and disease. Because mucus-secreting surfaces of almost any organ, but especially the digestive, genital, and respiratory tracts, are constantly exposed to a wide variety of harmful microorganisms, they are supported by secondary lymph structures. The specialized lymphoid tissue in the small intestine, peyer's patches, detect antigens such as bacteria and toxins and mobilizes highly specialized white blood cells termed B-cells to produce protein structures called antibodies that are designed to attack foreign particles.