Does the Failure to Acquire Helminthic Parasites Predispose to Ibd ?

Two polarized patterns (Th1 and Th2) of cytokines, secreted by stimulated lymphocytes, regulate inflammatory responses. Each cytokine pattern inhibits production of the opposing pattern. Lymphocytes from inflamed intestine due to Crohn’s disease secrete a Th1 pattern of cytokines. Crohn’s disease is most prevalent in highly industrialized countries with temperate climates. It occurs rarely in tropical third world countries with poor sanitation. This suggests that under exposure to an environmental agent may predispose individuals to Crohn’s disease. Parasitic worms (helminths) are common in tropical climates and in populations subject to crowding and poor sanitation. Children are most subject to helminthic colonization. Helminthic parasites live within the human gut where they interact with the mucosal immune system. The host mounts mucosal Th2 inflammation that limits helminthic infection or expels worms. Helminthic parasites and their eggs probably are the most potent stimulators of mucosal Th2 responses. The Th2 inflammation provoked by parasitic worms can modulate the immune response to unrelated parasitic, bacterial, and viral infections. Many people now live in increasingly hygienic environments avoiding exposure to helminthic parasites. Perhaps failure to obtain these parasite infections and experience mucosal Th2 conditioning during childhood predisposes to Crohn’s disease, which is an overly active Th1 inflammation