High affinity rheumatoid factor transgenic B cells are eliminated in normal mice

Area of Science:

• Immunology
• Autoimmunity
• B cell biology

Background:

• Systemic autoimmune diseases feature dominant autoantibodies like rheumatoid factors (RFs).
• Previous studies created an RF Ig transgenic model (AM14) in MRL/lpr mice, revealing normal mice do not regulate disease-related RF B cells.
• This raised questions about RF tolerance induction, possibly due to serum IgG and FcR properties or affinity thresholds.

Purpose of the Study:

• To investigate the tolerance mechanisms of RF B cells in normal and autoimmune settings.
• To determine if RF B cell tolerance is generally defective or dependent on autoantibody affinity.
• To establish a model for comparing RF B cell tolerance in antigen-positive and negative mice.

Main Methods:

• Generation of a second RF Ig transgenic model with higher affinity than the AM14 model.
• Comparison of B cell tolerance induction between the high-affinity RF model and the AM14 model.
• Analysis of central tolerance mechanisms in RF B cells based on affinity.

Main Results:

• High-affinity RF B cells, unlike lower-affinity RFs in the AM14 model, are subject to central tolerance in normal mice.
• Demonstrates that RF B cell tolerance is not absolutely defective but is dependent on the affinity of the RF.
• Provides the first model clearly showing deletion of a disease-related specificity in a system allowing comparison of antigen-positive and negative mice.

Conclusions:

• RF B cell tolerance is affinity-dependent, with higher affinity autoantibodies being susceptible to central tolerance.
• There is no inherent defect in RF B cell tolerance; rather, it is regulated by autoantibody affinity.
• This study establishes a crucial model for understanding the regulation of autoantibody production in autoimmune diseases.