Detection of Mtb-specific CD4+ T cells in peripheral blood. Eight QuantiFERON-TB Gold Positive patients with latent tuberculosis (LTBI) and eight QuantiFERON-TB Gold negative healthy controls (HC) were tested for response to a pool of ESAT-6 or CFP10 epitopes. (A) IFNγ ELISPOT of PBMCs from LTBI patients and healthy controls (*, p=0.0035 for ESAT-6, *, p=0.013 for CFP10). Limit of detection denoted by the grey dotted line. (B) AIM assay (CD25+OX40+) of PBMCs from LTBI patients and healthy controls similarly had higher CD25+OX40+ expression by AIM assay (*, p=0.027 for ESAT-6, ****, p<0.0001 for CFP10). Limit of detection denoted by the grey dotted line. Representative flow cytometry plots of CD25+OX40+ by an LTBI patient and a HC patient.