Immunopathogenesis of toxoplasmosis

Toxoplasmosis is a ubiquitous infection affecting 500 million persons around the world, with a range of incidence 12%-90%, increasing with age, education, crowding and sanitary habits. Cats are the definitive host. Infection is primarily congenital but acquired ocular infection has been documented. The review focuses on the immunopathogenesis of toxoplasmosis with emphasis on the eye problem due to its morbidity. The response to infection correlates with both parasitic and retinal antigens. The clinical picture and histopathology is a reflection of the immune response which constitutes early humeral response which presents both systemically and locally primary infection and is elevated with reactivation. This is followed by the cellular response, varying from low grade monocular infilterate a total tissue destruction with response of live parasites especially in immuno-compromised patients. Penetration of the parasite and its enclosure within the parasitophorous vacuole and its eneyst all make its eradicatier impossible. This reflects the variability of antiparasitic therapy that include folate antagonists, macrolides, hydroxy naphthoquindones and fluoroquinolones. Use of corticosteroid should be limited to severe reactions and should be associated with specific therapy.