RECENT ADVANCES IN THE IMMUNOLOGY OF CESTODE INFECTIONS

The economic and public health significance of tapeworm infections has provided impetus for the intensive study of cestode immunology, and some very encouraging advances have been made. Specific components of the protective mechanism have been defined in experimental hosts, and reproducible means of stimulating resistance artificially have been developed in domesticated and laboratory animals. Methods have been devised for the cultivation of postembryonic larvae so that antigenic products can be collected and characterized, and the interaction between parasites and immunological effector mechanisms may be studied in vitro. Further definition of metacestode antigens may enhance the specificity of immunodiagnostic procedures for human and animal taeniiasis so that reliable and practical tests can be devised, comparable to those now used in human hydatidosis. The ability of established metacestodes to evade immunological rejection is still perplexing. However, the very striking effectiveness of protective responses to challenge infection makes it possible to identify those elements of the host reaction which must be avoided by successful parasites. Cestode infections, therefore, offer unique advantages over other metazoan systems for the experimental analysis of concomitant immunity. Immunological responses in definitive hosts appear to be much more subtle, but the recent development of convincing ways to demonstrate their influence on adult parasites represents an important step toward understanding the rejection or prolonged survival of intestinal tapeworms as well.