This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
The antibody responsible for heparin induced thrombocytopenia is: 
Select and explain. 
A. Antiheparin / PF4 antibody, B. Antiheparin / PF2 antibody, C. Antiheparin / GP IIb/IIIa antibody, D. Antiheparin GP Ib/IX antibody
A: Antiheparin / PF4 antibody
Answer: A: Antiheparin / PF4 antibody 
Explanation: HIT results from antibody formation to a complex of the platelet specific protein platelet factor 4 and heparin. Ref: Harrisons principles of internal medicine, Edition -18, Page - 967.