Cold agglutinin disease is characterized by IgM autoantibodies that agglutinate red cells optimally at 4°C. These antibodies most commonly have specificity against which antigen?
- A Rh antigen
- B ABO blood group antigen
- C I antigen (polylactosamino carbohydrate) ✓
- D Kell antigen
Correct answer: C. I antigen (polylactosamino carbohydrate)
Explanation
Cold agglutinin disease predominantly involves IgM antibodies directed against the I antigen (a carbohydrate epitope) on the red cell surface. In mycoplasma pneumoniae-related cases, anti-I antibodies predominate; in infectious mononucleosis (EBV), anti-i antibodies are seen. These IgM antibodies activate complement (C3b) causing extravascular hemolysis in the liver. Rh, Kell, and ABO antigens are targets in warm autoimmune hemolytic anemia or alloimmune hemolysis.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.