RT Journal
A1 LoBue PA, Castro KG
T1 INterferon-γ-release assays for latent tuberculosis—reply
JF JAMA
JO JAMA
YR 2012
FD November 21
VO 308
IS 19
SP 1971
OP 1971
DO 10.1001/jama.2012.12826
UL http://dx.doi.org/10.1001/jama.2012.12826
AB 
In addition to measuring response to simulated Mycobacterium tuberculosis antigens, IGRAs also incorporate a negative control (response to solution with no antigens) and positive control (response to a nonspecific mitogen). It is expected that a large majority of persons with intact immunity will respond by producing interferon γ when exposed to the mitogen, so the mitogen response serves as a crude measure for assessing overall cell-mediated immunity.