Gram-positive pathogenic bacteria induce a common early response in human monocytes

Area of Science:

• Immunology
• Cell Biology
• Microbiology

Background:

• Investigates the early transcriptional response of human peripheral monocytes to live gram-positive bacteria.
• Utilizes three clinically significant species: Staphylococcus aureus, Streptococcus pneumoniae, and Listeria monocytogenes.
• Focuses on monocyte-intrinsic responses, avoiding confounding signals from other immune cells or bacterial components.

Purpose of the Study:

• To characterize the unbiased, early transcriptional response of human monocytes to infection with key gram-positive bacterial species.
• To identify common and distinct molecular pathways activated in monocytes upon encountering different bacterial pathogens.
• To explore novel roles of monocytes in host defense beyond direct pathogen clearance.

Main Methods:

• Infection of freshly isolated human peripheral monocytes with live Staphylococcus aureus, Streptococcus pneumoniae, and Listeria monocytogenes.
• Analysis of early transcriptional changes using expression microarrays.
• Bioinformatic analysis to identify upregulated genes and pathways.

Main Results:

• Monocyte activation characterized by upregulation of chemokine genes and notably, interleukin-23 (IL-23).
• Evidence of cytoskeleton rearrangement, anti-oxidative stress, and anti-apoptotic responses.
• 发现monocytes regulate angiogenesis and endothelial function in response to bacterial pathogens.

Conclusions:

• A consistent and common early transcriptional response was observed across different gram-positive bacterial species.
• Interleukin-23 (IL-23) emerged as a key early cytokine, even in response to Listeria monocytogenes, challenging previous associations.
• The findings highlight a broader role for monocytes in host defense, including vascular regulation during infection.