Monoclonal antibodies to HLA-B27

Area of Science:

• Immunogenetics
• Molecular immunology
• Rheumatology

Background:

• The human leukocyte antigen (HLA)-B27 is a critical genetic marker associated with susceptibility to spondyloarthropathies.
• Understanding HLA-B27 variations is crucial for diagnosing and managing related autoimmune diseases.

Purpose of the Study:

• To develop and characterize murine monoclonal antibodies for precise detection of HLA-B27 alloantigens.
• To investigate epitope variations within the HLA-B27 molecule and their potential association with disease.

Main Methods:

• Generation and characterization of two murine monoclonal antibodies, B27M1 (IgG2a) and B27M2 (IgM), targeting HLA-B27.
• Lymphocytotoxicity assays and cytotoxicity blocking studies to define antibody binding sites and cross-reactivity.
• Immunochemical analyses, including isoelectric focusing and size determination, to differentiate HLA-B27 variants.

Main Results:

• B27M1 reacts with all tested B27 antigens and shows minor cross-reactivity with B7.
• B27M2 reacts with >85% of B27 antigens, identifying a distinct epitope not present on all B27 variants and lacking B7 cross-reactivity.
• Immunochemical differences were observed between B27M2-positive and B27M2-negative HLA-B27 variants.
• Preliminary data suggest B27M2-negative B27 variants may be more strongly associated with ankylosing spondylitis.

Conclusions:

• A model for HLA-B27 is proposed, featuring a constant B27M1 epitope and a variable B27M2 epitope present in some individuals.
• The B27M2 epitope variation may represent a significant factor in HLA-B27 associated disease susceptibility, particularly ankylosing spondylitis.