Apoptosis

Metazoa are known to possess a sophisticated machinery of programmed cell death (PCD), which limits the life span of cells and prohibits cell exaggeration leading to tumors. Recently PCD has also been found in parasitic protozoans, e.g., in trypanosomes, malaria parasites, leishmanian species, trichomonads. As apoptotic markers had been described: chromatin condensation, DNA fragmentation, externalization of phosphatidylserine, and caspase-like activities. This way of self-limitation in protozoans is much less complex than in metazoan. It brings the advantage to these parasites, that they do not lose their hosts by killing them, before a small part of the population has been transferred to the next host. Thus the parasite density in a host does not rely exclusively on the host’s immune system. Since the apoptosis of protozoans is different from that of metazoans, it might be used as target for new chemotherapeutics.

However, intracellular parasites have also developed methods to...