Neutrophil swarming toward Cryptococcus neoformans is mediated by complement and leukotriene B4

Area of Science:

• Immunology
• Microbiology
• Cell Biology

Background:

• Neutrophil swarming is observed in sterile injury and infection, but in vitro models are lacking.
• Cryptococcus neoformans is a fungal pathogen causing meningoencephalitis.

Purpose of the Study:

• To establish an in vitro model for studying neutrophil swarming towards microbes.
• To elucidate the mechanisms of neutrophil swarming in response to Cryptococcus neoformans.

Main Methods:

• Live-cell imaging to observe neutrophil behavior.
• In vitro assays using neutrophils and Cryptococcus neoformans.
• Pharmacological blockade of LTB4 synthesis.
• In vivo mouse model of pulmonary Cryptococcus neoformans infection.

Main Results:

• Successfully observed in vitro neutrophil swarming towards Cryptococcus neoformans.
• Complement C3 and CD11b expression were essential for neutrophil swarming.
• Leukotriene B4 (LTB4) release by neutrophils was critical for swarming.
• Blocking LTB4 synthesis inhibited both in vitro swarming and in vivo neutrophil recruitment in mice.

Conclusions:

• This study presents the first in vitro model of neutrophil swarming towards a microorganism.
• Complement and LTB4 are key mediators of neutrophil swarming against Cryptococcus neoformans.
• LTB4 plays a critical role in intravascular neutrophil recruitment during fungal infection.