Opsonization and intracellular killing of Toxoplasma gondii by human mononuclear phagocytes.

Macrophages and monocytes have been shown to have an important role in the defence mechanism against Taxoplasma gondii infection. Antibodies in the presence of complement have been found capable of killing extracellular T. gondii. This study demonstrated that tachyzoites in the presence of antitoxoplasma antibodies with complement were detected in 39-58% of monocytes that had phagocytosed them and the mean number of Toxoplasma tachyzoites in this group was significantly low one hour post infection, while only 10-25% of monocytes phagocytosed Toxoplasma tachyzoites in absence of antibodies and complement with significant high number of replicated tachyzoites. This indicated that specific antibodies had a strong opsonizing action. Complement alone was weak in increasing the phagocytic activity.