Proliferation of Toxoplasma gondii in human neutrophils in vitro

Human neutrophils were infected with tachyzoites of Toxoplasma gondii in vitro. Infection rates after 1 h of incubation were 38.6-52.0% and 16.0-25.8% in the presence or absence of specific antibody respectively. Apparently, neutrophils killed tachyzoites 18 h after infection in the presence of antibody, whereas tachyzoites proliferated in 25.0-35.0% of infected neutrophils in the absence of antibody. Total tachyzoite counts 18 h after infection were approximately 4 times as high as those 1 h after infection in the absence of antibody and complement. Complement also enhanced phagocytosis and killing of tachyzoites by neutrophils, but the effects were less than that of antibody. Superoxide anion was produced intensively within 1 h after infection, depending on the presence of antibody or complement. Neutrophils seem to be responsible for dissemination of tachyzoites in the host during the initial phase of Toxoplasma infection until antibody is produced.