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: Pathology
[{'content': 'All of the following are Integrin molecules except____. \nSelect and explain. \nA. LFA-1, B. MAC-1, C. VLA-4, D. CD 31', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Platelet endothelial cell adhesion molecule-1 (PECAM-1) (also called CD31), an adhesion molecule of the immunoglobulin (Ig) superfamily\xa0 expressed\xa0 on\xa0 leukocytes\xa0 and\xa0 endothelial\xa0 cells,\xa0 mediates the binding events needed for leukocytes to traverse the endothelium.', 'role': 'assistant'}]