Re-thinking the functions of IgA(+) plasma cells

Area of Science:

• Immunology
• Microbiology
• Gastroenterology

Background:

• The intestinal mucosa contains the highest concentration of antibody-secreting plasma cells (PC) in the body, producing immunoglobulin A (IgA).
• IgA is crucial for mucosal immunity, protecting against pathogens and toxins, shaping the gut microbiota, and maintaining host-commensal balance.
• Commensal bacteria colonization is vital for IgA production, with reduced IgA+ PC numbers observed in germ-free (GF) animals and neonates.

Purpose of the Study:

• To review the mechanisms of IgA+ PC generation, survival, and functions in the gut.
• To highlight the roles of innate immune molecules like tumor necrosis factor α (TNFα) and inducible nitric oxide synthase (iNOS) in IgA+ PC homeostasis.
• To discuss emerging functions of PC beyond antibody secretion in inflammation and infection.

Main Methods:

• Review of existing literature on IgA+ plasma cells, gut immunity, and commensal interactions.
• Analysis of studies investigating the roles of TNFα and iNOS in IgA+ PC regulation.
• Exploration of recent findings on non-canonical functions of plasma cells.

Main Results:

• Commensal colonization is essential for IgA+ PC homeostasis.
• TNFα and iNOS are critical innate immune mediators for IgA+ PC maintenance during steady state and infection.
• Plasma cells possess functions independent of antibody secretion, relevant to inflammation and infection.

Conclusions:

• IgA+ plasma cells are central to intestinal mucosal immunity, with their generation and survival tightly regulated by commensal signals.
• Innate immune molecules TNFα and iNOS play indispensable roles in maintaining IgA+ PC populations.
• The multifaceted roles of plasma cells, including antibody-independent functions, warrant further investigation in the context of gut health and disease.