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.
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.
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.
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.