During the blood infection stage, in response to the presence of the parasite, the host's immune system releases a number of proinflammatory molecules including IL-1β, IL-6, IL-8, IL-12 (p70), IFN-γ, and TNF, all cytokines which play a defining role in controlling the parasite's growth and elimination (Figure 2). The gene discussed is TNF; the disease is infection.