Isolation of an IgG monoclonal anti-dnaJ antibody from an immunoglobulin combinatorial library from a patient with rheumatoid arthritis

Objective. Previously, we showed that rheumatoid arthritis (RA) had both an tibodies and T cells specific for the QKRAA-encompassing Escherichia coli d naJ protein. These findings suggest that the bacteria induced anti-dnaJ res ponses may cross react with the human homolog of bacterial dnaJ in the join t, resulting in tissue damage. Methods. We used the combinatorial library technique to isolate and charact erize 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 Vk 1 genes. Interestingly, 3d279d is frequently expressed by B cells stimulate d 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 i nteresting model of how to approach the isolation and characterization of a ntibody-like reagents in the elucidation of autoantigens in RA.