The immunological aspects of parasitic diseases.

Parasitic infections present a paradoxal immune situation: the host develops a normal immune response against the parasite but, in general, this response does not result in its elimination. An equilibrium is established which is essential to the survival of the parasite, involving a diminished state of the host, but not necessarily lethal. The mechanisms that allow the parasite to escape the immune defence are varied and include antigenic variation, mimetism, anatomical seclusion, immunomodulation, etc.