This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Inflammatory Bowel Disease, Subject name: Medicine
Which of the following is the established biological therapy for Crohn's disease? 
Select and explain. 
A. Anti TNF a antibody, B. IL - I antagonist, C. IL - 6 antagonist, D. IL - 8 antagonist
A: Anti TNF a antibody
Answer: A: Anti TNF a antibody 
Explanation: Tumor Necrosis Factor (TNF) is a key inflammatory cytokine and mediator of intestinal inflammation. The expression of TNF is increased in IBD. Infliximab is a chimeric human monoclonal antibody against TNF that is extremely effective in Crohn's disease. Recently adalimumab has also been approved for treatment of moderate to severe crohn disease. Newer Immunosuppressive Agents for IBD Tacrolimus Mycophenolate mofetil 6-Thioguanine Thalidomide