Peyer’s patches are required for oral tolerance to proteins
Oral tolerance is a method of treating certain diseases, most commonly allergies, by which a small amount of a substance that the patient is sensitive to is taken orally. This substance than is exposed to the immune system centered around the GI tract, and the immune system downregulates the response to this substance (tells the rest of the body that this substance is okay). This approach has also been used with rheumatoid arthritis patients with very good results.
PNAS — Abstracts: Fujihashi et al. 98 (6): 3310