Impedins are microbial pathogenicity factors that successfully evade or completely prevent host defense. This includes the ability to mimic host antigens and thereby evade the immune response. This is referred to as molecular mimicry. The immune response against the "own" antigens is usually absent or leads to a severe autoimmune disease. An example is the Coxsackie virus in connection with a heart muscle antigen, as well as Yersinia with regard to the HLA-B27 antigen.