Cytokine concentrations and responses measured with a commercial ELISA.

Median background IFN-γ concentrations (Nil, pg/mL) and IFN-γ responses (pg/mL) to phytohemagglutinin (Mitogen Response), early secreted antigenic target-6 (ESAT-6 Response), culture filtrate protein 10 (CFP-10 Response), TB7.7 (TB7.7 Response), and combinations of these M. tuberculosis (Mtb) antigens (ESAT-6+CFP-10 Response, and ESAT-6+CFP-10+TB7.7 Response) are listed with ranges in parentheses. Cytokine concentrations were measured with a commercial enzyme-linked immunosorbent assay (ELISA) for patients with culture-confirmed tuberculosis (patients) and subjects at low-risk of Mtb exposure (controls). Responses were calculated by subtracting the background cytokine concentration in plasma from blood incubated with saline (Nil) from the cytokine concentration in plasma from blood incubated with mitogen or Mtb antigens. N = 21 for patients and N = 24 for controls unless indicated (*n = 20, **n = 23). P values were calculated by Mann-Whitney U Rank Sum test comparing cytokine concentrations or responses for patients with controls. Significant differences (pbold type.