Neutrophils have been shown to control T. gondii infection, which is chronically in approximately one-third of the human population. T. gondii infection is established in the small intestine from consumption of contaminated food or water and after entering of the bloodstream, T. gondii disseminates through different organs, also with the help of infected immune cells to reach immunoprivileged sites (for more on neutrophils read – Neutrophils on Immunopaedia).
Mice are a natural intermediate host for T. gondii and therefore became a popular model to study immunological host defense. However, mice and humans have not always the same immunological mechanisms and studies of human neutrophils in T. gondii infection are scarce. Miranda et al. now determined the activation status of human neutrophils from patients with acute and chronic infections of T. gondii by flow cytometry. Additionally, they investigated the induction of neutrophil extracellular trap (NET) formation, the production of cytokines/chemokines and the recruitment of adaptive effector cells upon T. gondii stimulation (Figure 1).
Neutrophils from acute infected patients were significantly activated as shown by the upregulation of CD66b and the presence of CD66+CD16+ cells in the PBMC fraction. Transmission electron microscopy further revealed that tachyzoites actively infect neutrophils probably through phagocytosis. Moreover, the frequency of NET formation and ROS production was increased in neutrophils from healthy donors exposed to T. gondii. These NETs further amplified the innate immune response by promoting the migration and activation of neutrophils as shown using NET supernatants. Importantly, the T. gondii induced NETs not only activated more neutrophils but amplified also the adaptive immune response by attracting T cells and inducing the production of inflammatory cytokines by PBMCs.
Journal Article: Miranda, et al., 2021. Toxoplasma gondii-Induced Neutrophil Extracellular Traps Amplify the Innate and Adaptive Response. American Society for Microbiology.
Summary by Dr. Jasmin Knopf (Friedrich-Alexander-University of Erlangen-Nürnberg, Rheumatology and Immunology Clinic)