QuantiFERON Technology

The basis of QuantiFERON technology
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).

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Recall response reacts to specific markers
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) 

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Advantages of QuantiFERON technology
The advantages of QuantiFERON include the use of undiluted whole blood and the detection and measurement of IFNγ in undiluted plasma samples. QuantiFERON assays are accurate and sensitive in whole blood and undiluted plasma (1).

The use of whole blood in QFN methods makes T cell incubation simple and fast. There is no tedious lymphocyte isolation, washing, counting, diluting, or culturing. Just shake each tube and incubate 16–24 hours. The simple blood incubation allows processing of a very large number of samples. Logistics are very simple and the QFN method allows virtually labor-free incubation at nearly every location. QFN preserves the in vivo cellular and biochemical environment for lymphocyte stimulation, maximizing cellular responses. The technology is designed for clinical screening of large sample numbers, providing the standards, controls, and assay reproducibility needed for clinical diagnosis.(1)

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References

1. QFT Package Insert, March 2013, US05990301L. 
2. Silverman, M.S., Reynolds, D., Kavsak, P.A., Garay, J., Daly, A., Davis, I. (2007) Clin. Biochem. 40(12), 913. 
3. Berry, M.P. et al. (2010) Nature 466(7309), 973.
4. Nikolova, M. et al. (2013) Diagn. Microbiol. Infect. Dis. 75(3), 277.
5. Whitworth, H.S., Scott, M., Connell, D.W., Donges, B., Lalvani, A. (2013) Methods 61(1), 52. 

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QuantiFERON-TB Gold (QFT) is CE marked. QFT is approved by the US FDA.

QFT is approved by the FDA as an in vitro diagnostic aid for detection of Mycobacterium tuberculosis infection. It uses a peptide cocktail simulating ESAT-6, CFP-10, and TB7.7(p4) proteins to stimulate cells in heparinized whole blood. Detection of IFNγ by ELISA is used to identify in vitro responses to these peptide antigens that are associated with M. tuberculosis infection. FDA approval notes that QFT is an indirect test for M. tuberculosis infection (including disease) and is intended for use in conjunction with risk assessment, radiography, and other medical and diagnostic evaluations. QFT Package Inserts can be found at www.QuantiFERON.com.