This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacterial infection, Subject name: Medicine
Interferon gamma release assay measures IFN release against which M.TB antigen: 
Select and explain. 
A. ESAT 6, B. ESAT 7, C. CF 11, D. CF 12
A: ESAT 6
Answer: A: ESAT 6 
Explanation: Interferon gamma release assay (IGRA) measure T cell release of gamma interferon against TB antigen ESAT 6 and CF 10. This test also called as Quantiferon- more specific than Tuberculin skin testing as a result of less cross reactivity due to BCG vaccination and sensitization by nontuberculosis mycobacteria. - It reduces patient visits and gives an ability to perform serial testing without the hassle of boosting phenomenon caused by Tuberculin skin testing.