Related Experiment Videos
Rapid recruitment of neutrophils containing prestored IL-12 during microbial infection
S K Bliss1, B A Butcher, E Y Denkers
1Department of Microbiology and Immunology, Cornell University College of Veterinary Medicine, Ithaca, NY 14853, USA.
Abstract:
Neutrophils are well known to rapidly migrate to foci of infection, where they exert microbicidal functions. We sought to determine whether neutrophils responding to in vivo infection with the protozoan pathogen Toxoplasma gondii were capable of IL-12 production as suggested by recent in vitro studies. Intraperitoneal infection induced a neutrophil influx by 4 h, accompanied by ex vivo IL-12 p40 and p70 release. Approximately 85% of the neutrophils displayed intracellular stores of IL-12, as determined by flow cytometry and confocal fluorescence microscopy. Neutrophils from IFN-gamma knockout mice also expressed IL-12, ruling out an IFN-gamma-priming requirement. Neither infected nor uninfected peritoneal macrophages displayed intracellular IL-12, but these cells were strongly IL-10(+). Infection per se was unnecessary for IL-12 production because peritoneal and peripheral blood neutrophils from uninfected animals contained IL-12(+) populations. Expression of the granulocyte maturation marker Gr-1 (Ly-6G) was correlated with IL-12 production. Mice depleted of their granulocytes by mAb administration at the time of infection had decreased serum levels of IL-12 p40. These results suggest a model in which neutrophils with prestored IL-12 are rapidly mobilized to an infection site where they are triggered by the parasite to release cytokine. Our findings place neutrophils prominently in the cascade of early events leading to IL-12-dependent immunity to T. gondii.
Insights
Neutrophils rapidly release pre-stored interleukin-12 (IL-12) upon infection with Toxoplasma gondii. This IL-12 production by neutrophils is crucial for early immunity, independent of interferon-gamma (IFN-γ).
Area of Science:
- Immunology
- Cell Biology
- Infectious Diseases
Background:
- Neutrophils are key immune cells migrating to infection sites.
- Recent studies suggested neutrophils might produce IL-12, but this was unconfirmed in vivo.
Purpose of the Study:
- To investigate if neutrophils produce IL-12 during Toxoplasma gondii infection in vivo.
- To understand the role of neutrophils in early IL-12 dependent immunity.
Main Methods:
- Intraperitoneal infection model in mice.
- Flow cytometry and confocal microscopy to detect intracellular IL-12.
- Analysis of IL-12 production in neutrophils from IFN-gamma knockout mice.
- Depletion of granulocytes using mAb.
Main Results:
- Neutrophils rapidly infiltrated infection sites and released IL-12 (p40 and p70).
- Approximately 85% of neutrophils contained intracellular IL-12 stores, independent of IFN-gamma.
- IL-12 production was observed in neutrophils from uninfected animals, suggesting pre-stored cytokine.
- Depletion of neutrophils reduced serum IL-12 levels.
Conclusions:
- Neutrophils possess pre-stored IL-12, rapidly released upon parasite encounter.
- Neutrophils play a significant role in early IL-12-mediated immunity against Toxoplasma gondii.
- This highlights a novel function for neutrophils in initiating adaptive immune responses.