Quantitative light microscopic observations on Paneth cells of germ-free and ex-germ-free Wistar rats.

Germ-free rats were inoculated with bacteria from feces of SPF rats, and the Paneth cells in the ileal crypts were observed at different time intervals after inoculation. 12 h after inoculation, the Paneth cells showed a striking degranulation and the occurrence of supranuclear vacuoles. The Paneth cell area was significantly reduced. Four days to 3 weeks after inoculation, the secretory granules of Paneth cells were abundant, and both number and area of Paneth cells showed a progressive increase coming close to the data in SPF rats. The present study demonstrates interrelationships between secretory activity of Paneth cells and the microbial milieu in the small intestine and that the presently used experimental model is well suited for examining the histophysiology of Paneth cells. Moreover, the results suggest that Paneth cell numbers may also be closely related to crypt length.