<prompt> Interferon gamma release assay measures IFN release against which M.TB antigen:ESAT 6ESAT 7CF 11CF 12  <response>: 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. 