Interferon gamma assays for tuberculosis

The review states that both of these assays recommend that the cells from the person under investigation be incubated with the antigens for 24–48 hours, before the release of interferon γ is measured. The short incubation times are deliberate and crucially important, because only effector T cells that are already partly activated as a result of recent contact with antigen can secrete interferon γ so rapidly.2 Thus, these assays test for the presence within the host of metabolically active Mycobacterium tuberculosis, indicating latent or progressive infection. A definitive answer to these questions will require studies that directly compare the effect of incubation times on interferon γ responses from memory versus effector T cells both in latent infection and after antituberculosis treatment.