[The effect of toxoplasma antibodies after reinfection with T. gondii. III. Communication: investigations on the question of placental transmission of toxoplasma in immunised pregnant animals (author's transl)].

Investigations on whether theprotective effects of maternal defence mechanisms against T. gondii could prevent a placental transmission of the parasite to the foetus were carried out on pregnant rabbits and mice. With rabbits which were infected 6 to 1 month before the conception and showed a high infection immunity, there was never a transmission to the foetus and likewise at no time after reinfection of such maternal animals during the pregnancy. In mice which were latent infected with 11 different Toxoplasma strains, placental transmission succeeded with only 6 strains intrauterine infection of the foetuses were confirmed in 1 to 3%. After active immunisation of rabbits with non-multiplying antigen before the conception and later primary infection during the pregnancy, intrauterine transmission to the foetus could be detected in 55%. After passive immunisation with hyperimmune serum, infected foetuses could be ascertained in 79% of rabbits and 24% of mice. Possible intrauterine transmission to foetus protected by maternal defence mechanisms is likely to be dependent on various factors. 1. On the host species, 2. the state of immunity (infection immunity), 3. on Toxoplasma strain. An infection immunity with the presence of living parasites in maternal organism is probably dependent on Toxoplasma strain in mice and offers in rabbits an apparently certain protection against congenital infection. On the contrary, serologically detectable humoral antibodies after active or passive immunisation do not prevent a transplacental transmission. On the basis of experimental findings it has been concluded that at least the immunoglobulins of type IgG, IgA and IgM in lower titer ranges offer no protection against congenital transmission after reinfection during pregnancy. Also, the protective effect can not be based on the structure of respective placenta. The roles of cellular immune defence and other possible factors in this connection are discussed.