A Ahmed, NT Cheung, C Raykundalia, RD Situnayake, D Catty.
DnaJ (Heat Shock Protein) / Related Antigens, DR4 and Rheumatoid Arthritis.
J Coll Physicians Surg Pak Jul ;7(2):49-52.

Rheumatoid arthritis (RA) is an autoimmune disease which primarily occurs in HLA DR4 subjects. Several reports suggest the involvement of heat-shock proteins (HSPs) in RA. DnaJ, a HSP, of bacteria has been reported to possess a homologue sequence with DR4 haplotype suggesting the possible relationship between DnaJ, DR4 and RA. We have developed a monoclonal antibody (m-Ab) to DnaJ of Mycobacterium tuberculosis. The DnaJ antigen was detected in several Gram negative bacteria including Escherichia coli, Salmonella typhi, Klebsiella pneumoniae and Yersinia enterocolitica using the anti-DnaJ m-Ab in Western blot analysis. No cross-reactivity was noted with Staphylococcus aureus and Streptococcus pyogenes antigen. Anti-DnaJ mAb was also found to recognize three distinct antigens 38kDa, 43kDa and 60kDa in the DR4 human cell line. The RA patient`s serum immune complexes possess the DnaJ cross-reactive antigen around 38kDa and 60kDa which is not seen in normal subjects. This finding of homology between epitopes of DnaJ and some components of susceptible RA patients raises the possibility that induction of an antibody and/or T cell response to DnaJ might be implicated in an autoimmune process in which the DR4 is involved. The mechanism by which a shared epitope could increase susceptibility to RA is unknown and is likely to be complex.

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