This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bleeding disorders, Subject name: Pediatrics
[{'content': 'In Alloimmune thrombocytopenia antigen against which antibody is found? \nSelect and explain. \nA. HPA 1a, B. HPA 1b, C. HPA 2a, D. HPA 2b', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Neonatal alloimmune thrombocytopenic purpura (NATP): - Caused by development of maternal antibodies against antigens present on fetal platelets that are shared from father & recognized as foreign by maternal immune system. - The most common cause is incompatibility for the platelet alloantigen HPA-1a.', 'role': 'assistant'}]