Objective: Previously, we showed that rheumatoid arthritis (RA) had both antibodies and T cells specific for the QKRAA-encompassing Escherichia coli dnaJ protein. These findings suggest that the bacteria induced anti-dnaJ responses may cross react with the human homolog of bacterial dnaJ in the joint, resulting in tissue damage.
Methods: We used the combinatorial library technique to isolate and characterize an IgG monoclonal anti-dnaJ antibody (designated CG1) from the blood of a patient with RA.
Results: Sequence analysis of CG1 revealed that its heavy and light chain V regions were respectively most homologous to the 3d279d VH4 and the O18 Vk1 genes. Interestingly, 3d279d is frequently expressed by B cells stimulated with staphylococcal enterotoxin; and O18 is the main gene employed by the Vk1 IgG antibodies against Haemophilus influenzae.
Conclusion: The combinatorial immunoglobulin library method represents an interesting model of how to approach the isolation and characterization of antibody-like reagents in the elucidation of autoantigens in RA.