Intestinal changes associated with expression of immunity to challenge with Eimeria vermiformis

To provide more information on the mechanisms involved in the immune inhibition of eimeria infections, NIH mice were adoptively immunized against infection with Eimeria vermiformis by the transfer of mesenteric lymph node cells from primed animals and homologously challenged. Subsequent changes in the architecture and cellular composition of the intestine were compared with those observed in similarly challenged susceptible control mice and correlated with the development of the parasite in the two groups. Actively immunized mice were also examined. In adoptively immunized mice, the development of E. vermiformis was inhibited within 3 days of administering the challenge inoculum. Concurrent changes in the intestine included lymphocytic infiltration, crypt hyperplasia, flattening of the crypt epithelium, and a reduction in the number of Paneth cells. Hyperplasia of goblet and pyroninophilic cells in response to challenge, although accelerated and enhanced in adoptively immunized hosts, occurred after the inhibition of the parasites, and mastocytosis was not observed in these animals, findings which suggest that the activities of goblet, pyroninophilic, and mast cells were not instrumental in reducing the numbers of parasites. The intestines of immunized mice contained fewer intraepithelial lymphocytes at the time of inhibition of the parasites than did those of the controls. The protective effects and intestinal changes described above did not differ appreciably from those seen after challenge of mice that had been immunized by infection.