When a person is infected with MTB, their immune system sensitizes T-cells to recognize MTB-specific antigens. During an IGRA test, a blood sample is mixed with antigens from MTB. If the person is infected, their T-cells will release IFN-γ in response. The levels of IFN-γ are then quantified using enzyme-linked immunosorbent assay (ELISA) technology, providing a readout of the immune response.
