Structural features of nephritogenic lupus autoantibodies

Area of Science:

• Immunology
• Nephrology
• Molecular Biology

Background:

• Monoclonal antibodies from MRL-lpr/lpr lupus-prone mice induce nephritis upon passive transfer.
• Understanding the structural and immunochemical traits of nephritogenic immunoglobulin (Ig) is crucial for elucidating immune deposition mechanisms.

Purpose of the Study:

• To investigate the structural and immunochemical features of nephritogenic Ig that facilitate immune deposition.
• To compare antigen binding properties, immune deposit formation capacity, and nucleotide sequences within a genetically related autoantibody subgroup.

Main Methods:

• Passive transfer of monoclonal antibodies (e.g., H147, H257, H171, H8a) to normal mice.
• Analysis of glomerular and tubular basement membrane, and mesangial immune deposits.
• Evaluation of autoantibody binding to soluble autoantigens and cell surfaces.
• V gene sequence analysis of immunoglobulin heavy chains.

Main Results:

• The prototype antibody H147 induced glomerular, tubular basement membrane, and mesangial immune deposits, leading to proliferative glomerulonephritis.
• H257 also caused nephritis with similar immune deposits, while H8a formed predominantly mesangial deposits, and H171 showed minimal deposition.
• Only H147 and H257 bound to both mesangial and aortic endothelial cell surfaces, suggesting a role in targeting specific tissues.
• V gene sequence analysis indicated that specific residues, motifs, and conformations influence autoantigen binding and subsequent immune deposit formation.

Conclusions:

• Individual antibody features, including antigen binding specificity and tissue tropism, dictate the capacity for immune deposit formation and nephritis induction.
• Structural variations within the V gene influence autoantibody binding, contributing to differential pathogenic outcomes in lupus nephritis models.