Maintainence of parasitaemia - is it to die for?

Abstract

One of the major differences between protozoan differentiation and metazoan differentiation is that protozoan cells normally retain potency during differentiation, which need not, therefore, be considered altruistic. Altruism does, however, arise at the level of the organism and consequently, protozoons have the potential to evolve altruistic traits. This is particularly true when, as with Trypanosoma brucei parasitaemias, populations are genetically homogeneous. This essay argues that whilst reports of altruistic phenomena during the trypanosome life cycle remain controversial, the prospect of reagents able to instigate pathways of cell death or differentiation bears further investigation.

Figure 1

Dying stumpy forms? In bloodstream form populations taken from Balb/c mice at 120 h post-infection, approximately 1.2% (122 of 1000 trypanosomes counted) were stumpy by morphology and positive by diaphorase (a cytochemical marker of stumpy forms), but had a nuclear structure suggestive of a nuclear degradation. Such forms were not observed at earlier time-points during the parasitaemia.