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: Pharmacology
[{'content': 'Abtacept is used in treatment of which of the following conditions? \nSelect and explain. \nA. Rheumatoid ahritis, B. Asthma, C. Paroxysmal nocturnal hemoglobinuria, D. Autoimmune haemolytic anemia', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Abatacept is a recombinant fusion protein composed of the extracellular domain of cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) fused to human IgG Fc. CTLA-4 is a costimulatory molecule found on T cells that binds to CD80 and CD86 on antigen presenting cells. This fusion protein blocks activation of T cells by binding to CD80 or CD86 so that CD28 on T cells cannot bind and stimulate the T cell and lead to cytokine release. Abatacept is approved for patients with severe rheumatoid ahritis who have failed other disease-modifying antirheumatic drugs Ref: Katzung 11th edition Chapter 61.', 'role': 'assistant'}]