Two types of sheep Peyer's patches: location along gut does not influence involution.

In sheep, and some other species, there is evidence of two types of Peyer's patches (PPs), the ileal PP, which extends 150 cm along the terminal ileum, and the jejunal PPs distributed throughout the rest of the small intestine. The two types differ significantly in their histology, ontogeny and the extent of lymphocyte traffic. Another intriguing difference is that the ileal PP involutes about the time of puberty whereas the jejunal PPs function throughout life. This study shows that the differences in PP lifespan is not related to their specific location in the small intestine. Surgery was done at 1-2 months of age to transpose lengths of ileal PP into the jejunum, also, PP-containing lengths of jejunum were transposed into the midst of the ileal PP. Examination at age 12-16 months showed that ileal PP transposed into jejunum had involuted at the same rate as normally sited ileal PP. Also, jejunal PPs transposed into the ileum had not involuted unlike the surrounding ileal PP. It was concluded that the difference in lifespan of the two PPs were not related to the local microenvironment created by gut function, but may be inherent to the PP itself.