As an in vitro diagnostic technology able to provide information on the activity of the cell-mediated function of the immune system from whole blood samples, QuantiFERON technology aids in the detection of Mycobacterium tuberculosis infection.
The basis of QuantiFERON (QFN) technology is the stimulation of effector T cells in whole blood with a specific antigen(s) or mitogen, and the subsequent simple quantification of the resulting interferon-gamma (IFNγ) in the plasma. Using whole blood, QFN measures cell-mediated immune (CMI) responses to peptide antigens that stimulate mycobacterial proteins (1).
The QuantiFERON-TB Gold (QFT) test uses specialized blood collection tubes, that contain antigens representing certain M. tuberculosis proteins or controls, to collect whole blood via venipuncture (1). Incubation of the blood occurs in the tubes for 16 to 24 hours, after which, plasma is tested for the presence of IFNγ produced in response to the antigens (1).
Individuals exposed to disease/infection have specific T-cell lymphocytes in their blood that maintain an immunological memory for the antigens (immunologically reactive molecules) of the priming disease/infection (2–4). The addition of antigen to blood collected from a primed individual results in the rapid restimulation of antigen-specific effector T cells, resulting in the release of cytokines (e.g., IFNγ). Effector T cells are able to respond quickly when exposed to the priming antigen. Thus the production of IFNγ in response to antigen exposure is a specific marker for cellular immune response against that antigen (recall response). This IFNγ response may be used to quantify the recall response. (5)