The monoclonal anti–citrullinated protein antibody CCP-Ab1 present in patients with rheumatoid arthritis cross-reacts with both various autoantigens and many plant and microbial proteins, according to Dr. Reina Tsuda and associates.
The investigators determined that the essential epitope specific for CCP-Ab1 included six essential amino acid residues. They found that this epitope was shared by 38 human proteins, 56 viral proteins, 1,383 fungal proteins, 547 bacterial proteins, and 1,072 plant proteins. CCP-Ab1 reacted successfully with all of the epitope-sharing proteins, including proteins found in the environment, such as proteins consumed from plants as part of a regular diet.
While the wide variety of environmental factors suggest that RA should be more common, the generation of ACPA requires at least two prerequisite risk factors, and “citrullinated peptides more strongly interact with HLA-DR4 molecules and trigger strong CD4+ T cells activation. Thus, a minor population of subjects who have multiple risk factors may develop RA,” the investigators noted.
The full study is available in Arthritis & Rheumatology (doi:10.1002/art.39161).
