Experimental animal studies of the etiology and pathogenesis of Crohn's disease.

Nineteen New Zealand White Rabbits were inoculated intramurally into the intestine with a 100- or 0.2-mu filtrate of homogenate of fresh ileum or colon from each of 6 patients with histologically confirmed Crohn's disease and compared with 22 animals injected with homogenates of normal ileum or colon from each of 5 patients; 4 sham controls were also included. The animals receiving Crohn's homogenates put on less weight than the controls; mucosal ulceration, ileal thickening, and abscess formation were seen in 8 animals and granulomatous changes evolved in 9. No significant macroscopic abnormalities or granulomatous changes were present in any of the 22 control inoculated rabbits. Successful first passage was achieved from 6 of 11 rabbits. The results of these experiments therefore confirm and extend those of our earlier reports and demonstrate that the transmissible agent or agents responsible must approximate to the size of a virus or be capable of being deformed to pass through a 0.2-mu filter.