Which statement about the Donath-Landsteiner antibody is not a description of its classic properties?

Which statement about the Donath-Landsteiner antibody is not a description of its classic properties?

• A. Causes paroxysmal cold hemoglobinuria
• B. Binds to RBCs at 4C and causes hemolysis at 37C
• C. A biphasic, complement-binding IgM hemolysin
• D. None of the above

Answer: (C)

Donath-Landsteiner antibodies are biphasic hemolysins that cause paroxysmal cold hemoglobinuria. They bind red blood cells at cold temperatures (around 4°C) and, when warmed to 37°C in the circulation, fix complement and produce intravascular hemolysis. Importantly, these antibodies are of the IgG class, not IgM. Describing them as a biphasic, complement-binding IgM hemolysin does not fit their classic properties. The other notes—causing PCH and binding in the cold with hemolysis on warming—are accurate descriptors of these antibodies.

Donath-Landsteiner antibodies are biphasic hemolysins that cause paroxysmal cold hemoglobinuria. They bind red blood cells at cold temperatures (around 4°C) and, when warmed to 37°C in the circulation, fix complement and produce intravascular hemolysis. Importantly, these antibodies are of the IgG class, not IgM. Describing them as a biphasic, complement-binding IgM hemolysin does not fit their classic properties. The other notes—causing PCH and binding in the cold with hemolysis on warming—are accurate descriptors of these antibodies.