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
All of the following are Integrin molecules except____. 
Select and explain. 
A. LFA-1, B. MAC-1, C. VLA-4, D. CD 31
D: CD 31
Answer: D: CD 31 
Explanation: Platelet endothelial cell adhesion molecule-1 (PECAM-1) (also called CD31), an adhesion molecule of the immunoglobulin (Ig) superfamily  expressed  on  leukocytes  and  endothelial  cells,  mediates the binding events needed for leukocytes to traverse the endothelium.