Anticitrulline antibodies can be caused by homocitrulline-containing proteins in rabbits

Arthritis Rheum. 2010 Nov;62(11):3345-52. doi: 10.1002/art.27644.


Objective: To clarify the possible roles of protein-bound homocitrulline in causing an antibody response to citrulline and as a confounding factor in citrulline detection assays.

Methods: Native, carbamoylated, and citrullinated albumins were used for testing the specificity of commercial antibodies against modified citrulline by Western blot. Rabbits were immunized with human albumin and/or bone type I collagen, both of which were treated with cyanate to produce homocitrulline, or with citrullinated synthetic telopeptide of type I collagen. These antisera were tested for binding to cyclic citrullinated peptide 2 (CCP-2), mutated citrullinated vimentin, and type I or II collagen telopeptides containing either citrulline or homocitrulline.

Results: Commercial antibodies that had been considered to be specific for chemically modified citrulline were found to recognize both homocitrulline- and citrulline-containing albumins. The rabbits immunized with proteins containing homocitrulline produced high-affinity antibodies against CCP-2 and, to a lesser extent, against mutated citrullinated vimentin. The antisera also bound homocitrulline-containing collagen telopeptides and, less strongly, citrulline-containing telopeptides.

Conclusion: Our findings demonstrate that homocitrulline, which is a structural analog of citrulline (longer by 1 carbon, and readily formed in the body), can be involved in raising citrulline-recognizing antibodies in experimental animals and can cause false-positive reactions in assays for citrulline.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies / immunology*
  • Antibody Formation / immunology*
  • Blotting, Western
  • Chromatography, High Pressure Liquid
  • Citrulline / analogs & derivatives*
  • Citrulline / immunology*
  • Male
  • Rabbits


  • Antibodies
  • homocitrulline
  • Citrulline