Manipulation of apoptosis in the host-parasite interaction

Nearly all animal cells possess the capacity to undergo programmed cell death (apoptosis) when stimulated by an appropriate trigger. Apoptosis is crucial for maintaining social order among the cells comprising metazoans, but it also has other functions: the existence of apoptosis in single-celled organisms implies a degree of interaction between individuals and could perform the role of an 'immune' response. To survive within their hosts, parasitic protozoa and helminths demonstrate an ability to modulate host apoptosis pathways to their own advantage - preventing apoptosis in host cells that are inhabited by parasites and promoting apoptosis in host immune cells programmed to attack them. The manipulation of apoptotic pathways by parasites, as these relate to the interaction between parasite and host, forms the core of this review. The discussion concludes by suggesting that irradiated vaccines succeed in part as a result of apoptotic mechanisms.