Electron microscopic and radioisotopic studies on cap formation in Toxoplasma gondii.

Trophozoites of Toxoplasma gondii from mouse peritoneal exudate are capable of shedding antibodies with which they have been previously coated. The antibodies are first moved towards the anterior pole of the parasite, at which they form a "cap". From the pole they are shed into the environment in the form of antigen-antibody complexes. An internalization of the accumulated material has never been encountered. Most probably, the observed phenomenon reflects a mechanism by which the parasite evades the host's immune response.