IL-21 Shapes the B Cell Response in a Context-Dependent Manner

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Interleukin-21 (IL-21) is a T cell-derived cytokine vital for germinal center (GC) reactions.
• The specific functions of IL-21 signaling within B cells are not fully understood.

Purpose of the Study:

• To elucidate the B cell-intrinsic functions of IL-21 signaling.
• To investigate the impact of IL-21 receptor (Il21r) deletion on B cell responses.

Main Methods:

• Utilized a novel conditional knock-out mouse model lacking Il21r in B cells.
• Employed ex vivo B cell culture systems.
• Analyzed B cell populations and antibody responses in vivo after immunization.

Main Results:

• IL-21 induced Bim-dependent apoptosis in naive B cells but promoted proliferation in pre-activated B cells, especially IgG1+ B cells.
• B cell-specific Il21r deletion caused significant defects in IgG1 responses and impaired transition to the germinal center state.
• Il21r deficiency reduced IgG1+ B cells in plasmablast/plasma cell populations but not within germinal center B cells.

Conclusions:

• IL-21 signaling exhibits context-dependent effects on B cell fate, influencing both apoptosis and proliferation.
• IL-21 is a critical regulator of B cell differentiation and antibody production, particularly for IgG1 responses.