This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunomodulator, Subject name: Pharmacology
Abatacept is used in treatment of which of the following conditions? 
Select and explain. 
A. Rheumatoid Arthritis, B. Asthma, C. Paroxysmal nocturnal hemoglobinuria, D. Autoimmune Hemolytic Anemia
A: Rheumatoid Arthritis
Answer: A: Rheumatoid Arthritis 
Explanation: Ans. A. Rheumatoid ArthritisAbatacept is a fusion protein composed of Fc region of IgG1 fused to extracellular domain of CTLA-4. It inhibits the co-stimulation of T cells by blocking CD28-CD80/86 interactions. In order for a T cell to be activated, an APC must present two signals to the T cell. One of those signals is the MHC combined with the antigen, and the other signal is the CD80/CD86 molecule. Abatacept binds to CD80 and CD86 molecule and prevents second signal.Belatacept is FDA approved for kidney transplant recipients and is given monthly as an intravenous infusion.