The role of apoptotic mimicry in host-parasite interplay: is death the only alternative for altruistic behavior?

Multicellular organisms can clearly benefit from the noninflammatory elimination by apoptosis of unnecessary and potentially harmful cells. Recently accumulated data show that unicellular organisms such as pathogenic trypanosomatids can also take advantage of different apoptotic features [1]. As a matter of fact, similarities between multicellular organisms and the multicellular organization of unicellular organisms in the control of very basic mechanisms in cell physiology are not restricted to apoptosis, but extend to different cell biological phenomena such as cell-cycle control, multiplication, and differentiation [2]. Indeed, examples of mammalian-derived cytokines able to induce cell multiplication, protein phosphorylation, and protection from death in unicellular pathogenic trypanosomatids have been described [3,4]. These examples allow the postulation that the usage, by a population of unicellular parasites, of cellular and molecular processes normally operating in the host, is an efficient adaptive strategy. One such example is the capacity of different members of the genera Trypanosoma and Leishmania to take advantage of different features of the apoptotic process to establish a host-parasite relationship, without death as the necessary outcome. This will be the subject of the present commentary.