Low levels of natural killer cells in pregnant women transmitting Toxoplasma gondii

The role of cell-mediated immunity in the maternal-fetal transmission of Toxoplasma gondii was investigated in 17 pregnant women with primary T. gondii infection, in 7 of whom fetal infection occurred. 18 healthy pregnant women were followed-up as controls. Fetal outcome was uneventful in six women who were treated early in pregnancy with spiramycin, while stillbirth due to T. gondii encephalitis occurred in the offspring of one patient who started with therapy at 34 weeks' gestation. All patients who transmitted T. gondii showed significant changes in the mean levels of immune cells. The most prominent finding was a significantly lower level of natural killer (NK) cells in the mothers transmitting T. gondii to the fetus compared with non-transmitters and controls both in the number (99.7 (71.8-107.5)/microl versus 320.9 (307.9-356.4)/microl and 172.1 (122.4-213.3)/microl: median (25 degrees-75 degrees). p<0.001) and the percentage of NK cells (4.0+/-1.5 per cent versus 13.2+/-2.3 per cent and 10.2+/-3.4 per cent; mean+/-SD, p<0.001). Although limited by the small number of patients, our data suggest that the assessment of NK cells may be considered as a prognostic marker of primary T. gondii infection in pregnancy.