Conserved Epigenetic Programming and Enhanced Heme Metabolism Drive Memory B Cell Reactivation

Area of Science:

• Immunology
• Epigenetics
• Cell Biology

Background:

• Memory B cells (MBCs) are crucial for rapid and robust antibody responses upon secondary antigen exposure.
• Understanding the molecular mechanisms underlying MBC enhanced differentiation potential is key to improving vaccine efficacy and immunotherapy.

Purpose of the Study:

• To investigate the epigenetic landscape and transcriptional profiles of memory B cells (MBCs) to identify factors contributing to their heightened differentiation potential.
• To compare these signatures between human and mouse MBCs and explore the role of heme in MBC function.

Main Methods:

• Chromatin accessibility and transcriptome analyses were performed on influenza-specific IgM and IgG MBCs and naive B cells from mice and humans.
• Bioinformatic analyses identified differentially accessible regions and gene expression patterns.
• Functional assays assessed the impact of hemin on MBC differentiation and metabolism.

Main Results:

• MBCs exhibit an accessible chromatin architecture around plasma cell-specific genes and altered expression of key transcription factors and signaling pathway genes.
• A conserved MBC signature, including a heightened heme signature, was identified in both humans and mice.
• Hemin treatment enhanced oxidative phosphorylation and promoted MBC differentiation into antibody-secreting plasma cells.

Conclusions:

• Conserved transcriptional and epigenetic signatures in MBCs, involving heme and other pathways, underpin their enhanced reactivation potential.
• These findings provide insights into the molecular basis of immunological memory and suggest potential targets for therapeutic interventions.