- The studies summarized in this paper suggest that parasites may trigger activation of autoimmune mechanisms. The association between parasites and autoimmunity could by manifested by the development of pathogenic anti-parasitic antibodies and cytotoxic T cells that attack and damage self tissues as a result of molecular mimicry between host and parasites. On the other hand, the homology between self and parasitic antigens may enable parasites to protect themselves from the immune system and to induce a state of immunosuppression. Although classic autoimmune diseases have not been shown to be more common amongst patients with chronic parasitic infections than in the general population, it is clear that autoimmune activity does occur in patients with chronic parasitic infections. It is possible that infection with parasites and other microbial agents may be followed by the activation of the immune system and, in genetically predisposed individuals, by loss of functional tolerance to self, activation of autoreactive cell that leads to progression to an overt autoimmune disease.