IL-21/type I interferon interplay regulates neutrophil-dependent innate immune responses to Staphylococcus aureus

Area of Science:

• Immunology
• Microbiology
• Infectious Diseases

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) poses significant healthcare challenges.
• Understanding host immune mechanisms against MRSA is crucial for developing effective treatments.

Purpose of the Study:

• To investigate the role of Interleukin-21 (IL-21) in the innate immune response to MRSA pulmonary infections.
• To elucidate the interplay between IL-21 and type I Interferon (IFN) signaling in MRSA clearance.

Main Methods:

• Intra-tracheal administration of IL-21 in wild-type mice.
• Assessment of MRSA clearance with neutrophil depletion and granzyme B inhibition.
• Analysis of IL-21 receptor knockout (Il21r KO) mice and IL-21R-Fc fusion protein treatment.
• Evaluation of type I IFN pathway activation and its impact on MRSA clearance.

Main Results:

• IL-21 administration augmented pulmonary MRSA clearance in a granzyme-dependent manner, involving neutrophils.
• Blocking IL-21 signaling paradoxically enhanced MRSA clearance, associated with increased type I IFN activity.
• Type I IFN, specifically IFN-beta, induced granzyme B and promoted MRSA clearance independently.

Conclusions:

• IL-21 plays a complex role in MRSA innate immunity, promoting clearance through granzymes.
• Type I IFN signaling provides an alternative pathway for MRSA clearance, potentially compensating for IL-21 pathway modulation.
• An intricate interplay exists between IL-21 and type I IFN in controlling MRSA infections.