Arid1a-dependent canonical BAF complex suppresses inflammatory programs to drive efficient Germinal Center B cell...

Area of Science:

• Immunology
• Epigenetics
• Cell Biology

Background:

• B cells differentiating in germinal centers (GCs) need precise transcriptional and epigenetic changes for effective humoral immunity.
• Mammalian Brg1/Brm-associated factor (BAF) complexes regulate nucleosomal remodeling, vital for development, and are implicated in cancers like GC-derived B cell lymphomas.
• The specific roles of different BAF complexes in GC B cell biology and humoral immune responses remain unclear.

Approach:

• Investigated the role of the A-T Rich Interaction Domain 1a (Arid1a)-containing canonical BAF (cBAF) complex in GC B cell maintenance and humoral immunity.
• Analyzed the chromatin landscapes and gene expression programs in Arid1a-deficient B cells during GC responses.
• Assessed the impact of inflammation on GC B cell differentiation and the potential rescue by anti-inflammatory signaling.

Key Points:

• Arid1a-dependent cBAF complex is crucial for sustaining GCs and high-affinity antibody responses.
• Arid1a deficiency causes premature GC collapse due to failure to maintain the GC program.
• Arid1a-dependent cBAF activity establishes permissive chromatin and suppresses inflammatory genes, maintaining transcriptional fidelity in early GC B cells.
• Inflammatory signatures from Arid1a deficiency disrupt GC homeostasis by recruiting immune cells.
• Glucocorticoid receptor signaling can rescue GC B cell differentiation in Arid1a-deficient cells, underscoring inflammation's detrimental role.

Conclusions:

• Arid1a-dependent BAF activity is essential for efficient GC responses and humoral immunity.
• Unrestrained inflammation significantly impedes GC-derived humoral responses, as observed in severe infections.