These data reveal that innate MDSCs are induced not only during active TB at similar levels as found in cancer, but also in healthy individuals after recent exposure to M.tb. These cells diminish protective T-cell responses and may contribute to the inability of hosts to eradicate the infection and add to the subsequent development of TB disease.

Interferon gamma release assays (IGRAs) have been shown to be sensitive and highly specific for the detection of immune memory against Mycobacterium tuberculosis. Little is known about the reproducibility and within-person variability of these assays. Various aspects of short-term reproducibility of a commercial IGRA, the QuantiFERON-TB Gold In-Tube (QFT-IT) assay, were assessed. The QFT-IT assay was performed twice within 3 days in 27 health care workers in Cape Town, South Africa. Two sets of tests were performed by different operators on day 1, and one set was performed on day 3. Aspects such as interoperator, intraoperator, day-to-day variability, and test-retest variability as well as different the storage methods of plasma were investigated. Seventeen of 27 (63%)