It has been known for many years that bacteria can induce autoimmune responses in humans resulting in serious disease. Recent work has shown that a number of bacteria that colonize human mucosal surfaces exclusively express antigens on their surfaces which are molecular mimics of glycosphingolipids found on human cells. These structures are important in the pathogenesis of Neisseria and Haemophilus species for both immune evasion and in the adherence and invasion of human cells. There is no evidence that colonization or infections by these bacterial species is associated with autoimmune disease. © 2001 Academic Press.