Cold agglutinin disease is mediated by which immunoglobulin?

Cold agglutinin disease is mediated by which immunoglobulin?

• A. IgG
• B. IgA
• C. IgM
• D. IgE

Answer: (C)

Cold agglutinin disease involves autoantibodies that bind red blood cells at cold temperatures and trigger the complement system, leading to hemolysis. The antibody class that does this most effectively is IgM. Its pentameric structure lets it bind multiple RBC antigens at low temperatures and strongly activates the classical complement pathway (C1), driving hemolysis. This is why cold agglutinin disease is IgM-mediated. IgG can mediate warm autoimmune hemolytic anemia through Fc receptor–mediated processes, but that’s a different pattern. IgA and IgE are not typically involved in this condition.

Cold agglutinin disease involves autoantibodies that bind red blood cells at cold temperatures and trigger the complement system, leading to hemolysis. The antibody class that does this most effectively is IgM. Its pentameric structure lets it bind multiple RBC antigens at low temperatures and strongly activates the classical complement pathway (C1), driving hemolysis. This is why cold agglutinin disease is IgM-mediated. IgG can mediate warm autoimmune hemolytic anemia through Fc receptor–mediated processes, but that’s a different pattern. IgA and IgE are not typically involved in this condition.