The role of clonal selection and somatic mutation in autoimmunity

Area of Science:

• Immunology
• Autoimmunity
• Molecular Biology

Background:

• Polyclonal activation is a proposed mechanism for autoantibody production in autoimmune diseases.
• This model suggests a multiclonal, unmutated, or randomly mutated autoantibody population.
• It does not account for specific antigen selection of B cells.

Purpose of the Study:

• To investigate the origin and characteristics of immunoglobulin G (IgG) autoantibodies targeting self-IgG (rheumatoid factor, RF) in MRL/lpr mice.
• To determine if autoantibody production aligns with polyclonal activation or antigen-driven selection models.

Main Methods:

• Analysis of genetic features and clonal composition of spontaneously derived RF autoantibodies from MRL/lpr mice.
• Comparison of autoantibody characteristics with predictions from polyclonal activation models and experimental polyclonal activation outcomes.

Main Results:

• MRL/lpr RF autoantibodies are oligoclonal or monoclonal, contradicting the polyclonal activation model.
• These autoantibodies possess numerous somatic mutations, indicative of selection.
• Mutation patterns suggest immunoglobulin-receptor-dependent selection, similar to responses against exogenous antigens.

Conclusions:

• The findings challenge the polyclonal activation model for autoantibody generation in MRL/lpr mice.
• Antigen stimulation and selection processes, akin to secondary immune responses, appear crucial for generating MRL/lpr RF autoantibodies.
• This suggests a role for specific antigen selection in autoimmune B cell responses.