Mucosal or systemic microbiota exposures shape the B cell repertoire

Area of Science:

• Immunology
• Microbiome research
• Systems biology

Background:

• Microbiota colonization stimulates B cells and immunoglobulin production.
• Mammals exhibit complex, individualized immunoglobulin repertoires due to diverse microbial colonization.
• Understanding how the microbiota shapes B cell populations and their responsiveness is crucial.

Purpose of the Study:

• To deconstruct how defined microbial exposures shape the B cell pool and immunoglobulin repertoire.
• To investigate the distinct immune responses generated by mucosal versus systemic microbial exposures.
• To analyze the development and characteristics of immunoglobulin repertoires in response to microbial stimuli.

Main Methods:

• Utilized a simplified model of defined transient microbial exposures in germ-free mice.
• Employed deep sequencing to analyze immunoglobulin repertoires in B cell populations and single cells.
• Compared immune responses following intestinal mucosal and intravenous systemic microbial exposures.

Main Results:

• Microbial exposures at the intestinal mucosa induced oligoclonal responses distinct from germ-free controls.
• Intravenous systemic exposure generated a diverse immunoglobulin repertoire.
• Systemic exposure broadened the IgG repertoire to microbial antigens, while mucosal exposure led to restricted IgA repertoires and attrition of specificities.

Conclusions:

• Microbial exposures induce characteristic immunoglobulin heavy-chain repertoires in B cells, particularly in memory and plasma cells.
• Systemic microbial exposure promotes a flexible and diversified IgG repertoire, contrasting with a restricted IgA repertoire from mucosal exposure.
• These findings reveal distinct host-microbe immune dynamics, with systemic exposure favoring broad defense and mucosal exposure reflecting host-microbial mutualism.