The T-SPOT.TB test technology
1 small tube. 1 million ways to find the truth.1
The immune response to infection with Mycobacterium tuberculosis (MTB) is mediated predominantly through T cell activation. As part of this response, T cells are sensitized to MTB antigens and the activated effector T cells, both CD4+ and CD8+, produce the cytokine interferon-gamma when stimulated by these antigens. The T-SPOT.TB test uses the enzyme-linked immunospot (ELISPOT) methodology to enumerate M. tuberculosis-sensitized T cells by capturing interferon-gamma in the vicinity of T cells from which it was secreted.
When your test looks for signs of TB infection using T cells, it matters how many T cells you include. The T-SPOT.TB test, unlike other tests, uses the same number each time. And it’s a big number: 250,000 cells per well, four wells per test.1 That’s a million witnesses to infection – and a moment of truth for TB.
The principles of the T-SPOT.TB test:
Step 1
A blood specimen is collected using routine phlebotomy and a standard blood collection tube from which a subset of white blood cells, known as peripheral blood mononuclear cells (PBMC), are isolated. The cells are washed, counted and normalized to create a standard cell suspension.
Step 2
A standard number of cells are added into specially designed plates and stimulated with TB-specific antigens, ESAT-6 and CFP10. Cells responding to these antigens release interferon-gamma.
Step 3
Interferon-gamma antibodies are used to directly capture interferon-gamma as it is released by the cells. A secondary enzyme labeled antibody is added and binds to the captured interferon-gamma.
Step 4
A detection reagent is added and reacts with the enzyme labeled antibody. This reaction produces spots, which are a footprint of where the interferon-gamma was released. Spots are then enumerated.