Negative findings in search for a transmissible agent in Crohn's disease

Affected lymph nodes from 3 patients with Crohn's disease were homogenised and inoculated intramurally into the distal ileum of five piglets. The homogenates were also inoculated intramurally in the distal ileum of 15 rats and also by percutaneous injection intraabdominally in 15 rats and compared with the same number of animals of each species inoculated in the same manner with homogenates prepared from 3 patients with caecal cancer. There was no difference in weight increase between the animals inoculated with Crohn's tissue homogenate or control tissue homogenate. Neither did we find any macroscopic or microscopic changes in the animals inoculated with Crohn's tissue homogenate. We found a rather high frequency of mammary tumors in the rats inoculated with Crohn's tissue homogenate, although compared to the rats inoculated with control tissue homogenate there was no statistically significant difference. The negative results may be due to the method of preparing the tissue homogenate or to the use of lymph nodes instead of the bowel in preparing the homogenate, but may also be taken as support against the suggestion that a transmissible agent is present in Crohn's disease.