Unveiling signaling pathways inducing MHC class II expression in neutrophils.

Area of Science:

• Immunology
• Molecular Biology
• Infectious Diseases

Background:

• Gram-negative bacillary bacteremia is a severe infection leading to sepsis.
• Neutrophils play a key role, but their early-phase molecular mechanisms remain unclear.

Purpose of the Study:

• To investigate the phenotype and signaling pathways of human neutrophils in early gram-negative bacteremia.
• To identify molecular targets for sepsis treatment.

Main Methods:

• Unbiased proteomics and flow cytometry identified neutrophil phenotype.
• In vitro model used GM-CSF to induce APC-like phenotype in neutrophils.
• Downstream signaling pathways were analyzed.

Main Results:

• Neutrophils exhibited an antigen-presenting cell (APC)-like phenotype with MHC class II expression.
• GM-CSF induced MHC class II via MAPK-p38-MSK1-CREB1 and CIITA, dependent on JAK1/2 signaling.
• Key signaling pathways involved were JAK-STAT, MAPK, and PI3K-Akt-mTOR.

Conclusions:

• Neutrophils can adopt APC-like functions during bacteremia.
• JAK1/2 signaling is crucial for MHC class II induction in neutrophils.
• Targeting JAK1/2 signaling presents a potential therapeutic strategy for gram-negative bacteremia and sepsis.