This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pharmacology
Following monoclonal antibody is directed against alpha 4 integrin (REPEAT) 
Select and explain. 
A. Efalizumab, B. Natalizumab, C. Ibalizumab, D. Toclizumab
B: Natalizumab
Answer: B: Natalizumab 
Explanation: Natalizumab is anti-integrin monoclonal antibody used in ulcerative colitis, Crohn&;s disease and multiple sclerosis.Ref: Katzung 13th ed.pg 962.