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     Western blot analysis of CAD expression in HeLa cell lysate.    

  
  

CAD antibodies, primarily associated with autoimmune liver diseases, target specific intracellular enzymes involved in metabolic pathways. The term "CAD" refers to the trifunctional carbamoyl-phosphate synthetase 2. aspartate transcarbamylase, and dihydroorotase (CAD) protein, a key enzyme in pyrimidine biosynthesis. Initially identified in autoimmune hepatitis (AIH) and primary biliary cholangitis (PBC), these autoantibodies are detected via indirect immunofluorescence or immunoblotting.

CAD antibodies are part of a broader spectrum of antinuclear antibodies (ANA) but exhibit distinct cytoplasmic staining patterns. Their presence correlates with specific clinical subtypes, particularly in AIH type 1. where they may coexist with anti-SMA or anti-LKM1 antibodies. Though their exact pathogenic role remains unclear, CAD antibodies serve as diagnostic markers, aiding in differentiating autoimmune liver disorders from other hepatobiliary conditions.

Recent studies suggest CAD antibodies may also appear in systemic autoimmune diseases like rheumatoid arthritis or Sj?gren's syndrome, hinting at shared molecular mechanisms. Research continues to explore their prognostic value and relationship to disease activity. Despite low prevalence (5–15% in AIH), their identification enhances serological profiling, supporting personalized treatment approaches in autoimmune hepatology.