Autoreactive B-cell elimination by pathogenic IgG specific for the same antigen: implications for peripheral...

Area of Science:

• Immunology
• Autoimmunity
• Cell Biology

Background:

• Pemphigus vulgaris is an autoimmune blistering disease caused by pathogenic IgG autoantibodies against desmoglein 3 (Dsg3).
• Dsg3 is crucial for cell adhesion in skin and mucous membranes.
• Autoreactive B cells can escape normal tolerance mechanisms.

Purpose of the Study:

• To investigate the mechanisms of elimination for autoreactive B cells in pemphigus vulgaris.
• To determine the role of pathogenic autoantibodies and T cells in B cell tolerance.

Main Methods:

• Utilized AK7-transgenic mice expressing non-pathogenic IgM against Dsg3.
• Administered pathogenic IgG1 mAb (AK23) and non-pathogenic IgG mAbs (AK7, AK9).
• Employed Rag2(-/-) mice and T cell transfer experiments, including FasL mutant (gld) mice.
• Investigated the effect of Bcl2 overexpression on B cell elimination.

Main Results:

• Pathogenic anti-Dsg3 IgG1 mAb (AK23) eliminated autoreactive B cells when Dsg3 was present peripherally.
• Non-pathogenic IgG mAbs did not induce B cell elimination.
• AK23-mediated elimination was T-cell dependent in the periphery but T-cell independent in the bone marrow.
• Elimination required CD4+ T cells and Fas-mediated signaling.
• Bcl2 overexpression impaired B cell elimination.

Conclusions:

• Autoreactive B cells persist unless they pose a threat.
• Harmful autoreactive B cells are eliminated via a Fas-mediated, CD4+ T cell-dependent pathway.
• This mechanism acts as a safeguard against autoimmune tissue damage.