Clonal deletion provides an incentive for microorganisms to develop epitopes similar to proteins found within the host. Because most autoresponsive cells undergo clonal deletion, this allows microorganisms with epitopes similar to host antigen to escape recognition and detection by T and B lymphocytes. However, if detected, this can lead to an autoimmune response because of the similarity of the epitopes on the microorganism and host antigen. Examples of this are seen in Streptococcus pyogenes and Borrelia burgdorferi. It is possible, but uncommon for molecular mimicry to lead to an autoimmune disease.
