ABSTRACT
Parasites gain entry to the body along a variety of routes, through the skin, across mucosal surfaces, or by injection directly into the blood stream, and during their life cycles often utilize a combination of all three. A consequence of this is that parasites present not only a complex and considerable antigenic load to the host but also confront it at a number of distinct sites around the body. It follows, therefore, that the way in which the body handles antigen will depend upon the molecular nature of the antigen, the site of antigen exposure, the cell types which encounter the antigen and the immunoregulatory mechanisms operating in the host at that particular time.
