Apart from antibodies, another important line of parasite defence has been attributed to cytokines such as IFN-γ, IL-17 and IL-6, all of them playing a role in coordinating the innate and adaptive defence mechanisms of the host during infection with T. gondii. It is well established that IFN-γ is important to promote Th1-directed adaptive immune responses [31] and to control parasite replication during chronic infection [32, 33] via IFN-γ mediated NO synthesis in different host cells such as macrophages [34]. The gene discussed is IL17A; the disease is infection.