Adaptive Immunity

This chapter summarizes our current understanding of how the adaptive immune system recognizes and responds to Toxoplasma gondii infection. Following the first line of innate immune reactions, the adaptive immune system plays a crucial role in containing T. gondii infection mostly via the production of type I responses. The IL-12/IFN-γ axis and cytotoxic factors produced by CD8 T cells help the host survive during acute and chronic infection phases. Inadequate cellular immunity leads to uncontrolled parasite replication and severe disease. However, the adaptive immune system does not clear the parasite and T. gondii can persist in its mammalian host, ultimately facilitating transmission to other hosts. Proper balance of the adaptive immune response is the key for the survival of both parasite and host. Deficits in immune regulatory mechanisms cause immunopathology and tissue damage at the site of parasite entry (intestine) or persistence (brain).