Tissue-resident B cells orchestrate macrophage polarisation and function.

Area of Science:

• Immunology
• Cell Biology

Background:

• B cells are crucial for humoral immunity and have antibody-independent roles.
• Research has primarily focused on B cells in blood and lymphoid organs, leaving their presence in non-lymphoid organs (NLOs) unclear.

Purpose of the Study:

• To investigate the existence and function of tissue-resident B cells in NLOs during homeostasis.
• To determine the impact of these B cells on the immune microenvironment and host defense.

Main Methods:

• Utilized intravenous labeling and parabiosis techniques to identify and track B cells.
• Analyzed B cell populations in various NLOs including lung, liver, kidney, and urinary bladder.
• Investigated the interaction between tissue-resident B cells and macrophages.

Main Results:

• Identified a distinct population of tissue-resident B cells in multiple NLOs.
• Found that a significant proportion of these cells are B-1a cells.
• Demonstrated that tissue-resident B cells modulate macrophage polarization and function, promoting an anti-inflammatory phenotype via IL-10.
• Observed effects on bacterial clearance during urinary tract infection.

Conclusions:

• Tissue-resident B cells are present in NLOs and contribute to immune homeostasis.
• These B cells play a critical role in setting the inflammatory tone of myeloid cells.
• Findings have significant implications for understanding and manipulating tissue immunity.