IFNG and malaria: Experiments in animal models revealed that many T-cell effector mechanisms, such as perforin release [20], expression of death receptor Fas [20], secretion of interferon gamma (IFNγ) [19] or tumor necrosis factor alpha (TNFα) [21], are either redundant for or make highly variable contribution to vaccination-induced protection against malaria depending on a particular parasite/host combination.