IgG rheumatoid factors isolated by the surface-displaying phage library technique

Area of Science:

• Immunology
• Molecular Biology
• Rheumatology

Background:

• Rheumatoid factors (RFs) are autoantibodies implicated in rheumatoid arthritis (RA).
• Previous studies suggested antigen-driven selection of RFs in RA patients.
• The structural diversity and origins of IgG RFs in RA remain incompletely understood.

Purpose of the Study:

• To investigate the molecular characteristics of IgG rheumatoid factors (RFs) in rheumatoid arthritis (RA).
• To construct and analyze an IgG RF combinatorial antibody library from synovial fluid.
• To identify novel heavy and light chain variable regions of RFs in RA.

Main Methods:

• Construction of an IgG1,lambda combinatorial antibody library using the pComb3 vector.
• Panning the library against human IgG to select Fc-binding Fab fragments.
• Sequence analysis of selected Fc-binders to determine heavy (H) and light (L) chain variable (V) regions.

Main Results:

• Analysis of RFs from RA patients revealed skewed mutations in V regions, indicating antigen-driven responses.
• A combinatorial library yielded 71/96 Fc-binding clones, with 85% sharing identical H and L chain V regions (Humha311 and Humla211).
• Identified RF V regions differed from those obtained via hybridoma, and Humha311 H chain exhibited frameshifts leading to unconventional CH1 sequences.

Conclusions:

• IgG RFs in RA likely arise from antigen-driven responses.
• Novel IgG RFs with unique V region sequences, including unconventional CH1 regions, were identified.
• Further research is needed to explore the structural and immunological impact of these unconventional IgG sequences in RA.