Where Are All the Mycobacterium avium Subspecies paratuberculosis in Patients with Crohn's Disease?

Mycobacterium avium subspecies paratuberculosis (MAP) causes a chronic granulomatous inflammation of the intestines, Johne's disease, in dairy cows and every other species of mammal in which it has been identified. MAP has been identified in the mucosal layer and deeper bowel wall in patients with Crohn's disease by methods other than light microscopy, and by direct visualization in small numbers by light microscopy. MAP has not been accepted as the cause of Crohn's disease in part because it has not been seen under the microscope in large numbers in the intestines of patients with Crohn's disease. An analysis of the literature on the pathology of Crohn's disease and on possible MAP infection in Crohn's patients suggests that MAP might directly infect endothelial cells and adipocytes and cause them to proliferate, causing focal obstruction within already existing vessels (including granuloma formation), the development of new vessels (neoangiogenesis and lymphangiogenesis), and the “creeping fat” of the mesentery that is unique in human pathology to Crohn's disease but also occurs in bovine Johne's disease. Large numbers of MAP might therefore be found in the mesentery attached to segments of intestine affected by Crohn's disease rather than in the bowel wall, the blood and lymphatic vessels running through the mesentery, or the mesenteric fat itself. The walls of fistulas might result from the neoangiogenesis or lymphangiogenesis that occurs in the bowel wall in Crohn's disease and therefore are also possible sites of large numbers of MAP. The direct visualization of large numbers of MAP organisms in the tissues of patients with Crohn's disease will help establish that MAP causes Crohn's disease

Lymphatic vessel contractile activity and intestinal inflammation

Edema is a consistent observation in inflamatory bowel disease (IBD), and immune responses are inevitable in inflammation. Because the lymphatic system is an integral part of both tissue fluid homeostasis and immune reactions, it is likely that lymphatics play a role in the complex etiology of IBD. Despite the consistent findings that the lymphatic system is altered during gastrointestinal inflammation, the majority of studies conducted on the disease only mention the lymphatic system in passing. The effects of inflammatory mediators on lymphatic vessel function also remain poorly defined, despite its essential role in immunity and prevention of tissue edema. Processes allowing effective lymph transport are altered during inflammation, however, the mode of alteration and reason why lymphatics are ineffective in inflammatory reactions need to be further investigated. In addition, these processes have not yet been examined in an appropriate animal model and little has been done using in vivo methods of investigation in any model of gastrointestinal inflammation. This paper reviews the role of the lymphatic system in intestinal inflammation, as well as the role of the inflammatory products in mediating lymphatic contractile function