Further observations on the transmissibility of Crohn's disease.

In controlled experiments normal and immunologically deficient CBA mice were inoculated with whole fresh, fresh autoclaved, fresh supernatant, or filtered supernatant (0.2 mu) of whole Crohn's or non-Crohn's homogenate into footpads, intraperitoneally or intravenously. Epithelioid and giant-cell granulomas were present in a substantial proportion the footpads and in bowel or mesenteric lymph nodes of a proportion of given each fresh Crohn's homogenate by any of these routes 15-17 months after inoculation, but were not present in mice given non-Crohn's or autoclaved Crohn's homogenate. Successful passages were achieved following the inoculation of Crohn's mouse tissue homogenates, including passage from mice receiving filtered supernatant (0.2mu) or whole Crohn's homogenate, into footpads or intravenously. The epithelioid- and giant-cell granulomas evolved slowly over a period of many months following the inoculation of Crohn's tissue or passage homogenates and persisted thereafter. The transmissible agent is inactivated when homogenate from Crohn's tissue is autoclaved, can be passaged successfully into footpads or intravenously, and has been shown to pass an 0.2 mu membrane filter. It is therefore presumably viable and must approximate to the size of a virus or be capable of being deformed to pass a filter of such a pore size (0.2mu).