Abstract
It is now well established that animal parasites elicit vigorous immune responses in their hosts and that the resistance to reinfection thus acquired is mediated through conventional humoral and/or cellular effector mechanisms. It is also recognized, however, that some parasites exhibit extreme longevity in the face of a potentially hostile or lethal environment, and it may be assumed therefore that such organisms possess a repertoire of highly sophisticated and successful evasive strategies. Of all the survival mechanisms thus far proposed, the concept of antigen sharing, or disguise, is probably the most contentious. Arguments have arisen over the nature and origin of the shared determinants and over the validity of their role in ensuring parasite survival within the fully immunocompetent host. This presentation reviews published data concerning the existence of a disguise stratagem amongst medically important parasites and evaluates experiments designed to investigate the functional importance of disguise in immune evasion.