Elucidating the factors that play important roles in the expression of viru
lence by parasites is crucial to understanding disease pathogenesis and to
developing control strategies rationally. Here, Kate Miller, Nick Smith and
Alan Johnson, using Toxoplasma gondii as a model, argue that the interacti
ons between the immune system and 70 kDa heat shock proteins of apicomplexa
n parasites profoundly influence parasite virulence.