<s>[INST] context: Two major types of "cold antibody" may produce autoimmune hemolytic anemia. Cold agglutinins, which directly agglutinate RBCs, mediate cold agglutinin disease. The Donath-Landsteiner autoantibody, which is not an agglutinin but a potent hemolysin, mediates paroxysmal cold hemoglobinuria. - Cold agglutinin disease : In current usage, cold agglutinin disease peains to patients with chronic AHA in which the autoantibody directly agglutinates human RBCs at temperatures below body temperature, maximally at 0 to 5degC. IgM Ab against I Antigen of RBC. Attaches at cold temperatures resulting in clumping/ agglutination - Acrocyanosis Extravascular hemolysis is seen. - Cold Hemolysin type : The Donath-Landsteiner antibody is responsible for complement-mediated hemolysis in paroxysmal cold hemo-globinuria, a rare form of AHA in adults. The disorder is characterized by recurrent episodes of massive hemolysis following cold exposure. IgG Ab against P Antigen of RBC. Ab binds at 40 C ,complement system is activated at 370C Causes intravascular hemolysis. [/INST] question: Cold agglutinins are directly against which of the following RBC antigens? | options: A: P antigen B: I antigen C: Le antigen D: Rh antigen | answer: B </s>