During citrullination, the altered protein may be recognized by the immune system as:

During citrullination, the altered protein may be recognized by the immune system as:

• A. It is rapidly cleared
• B. It becomes tolerogenic
• C. An antigen
• D. It remains non-immunogenic

Answer: (C)

During citrullination, a post-translational modification converts arginine residues in proteins into citrulline, changing both charge and shape of the peptide. This creates new peptide epitopes that the immune system may not recognize as self, effectively turning the modified protein into an antigen. Antigen-presenting cells can process these citrullinated proteins and display the new epitopes on MHC class II molecules to CD4+ T cells, which can drive B cell responses and production of antibodies against citrullinated epitopes. This immunogenic potential is exemplified in diseases like rheumatoid arthritis, where anti-citrullinated protein antibodies are a hallmark. So the altered protein is recognized by the immune system as an antigen.

During citrullination, a post-translational modification converts arginine residues in proteins into citrulline, changing both charge and shape of the peptide. This creates new peptide epitopes that the immune system may not recognize as self, effectively turning the modified protein into an antigen. Antigen-presenting cells can process these citrullinated proteins and display the new epitopes on MHC class II molecules to CD4+ T cells, which can drive B cell responses and production of antibodies against citrullinated epitopes. This immunogenic potential is exemplified in diseases like rheumatoid arthritis, where anti-citrullinated protein antibodies are a hallmark. So the altered protein is recognized by the immune system as an antigen.