Memory γδ T cells produced IFN-γ in response to ESAT-6. (A) Several surface markers were included to define the phenotype of ESAT-6–specific γδ T cells. PBMCs were cultured in the presence of ESAT-6 plus anti-CD28 for 5 hours. IFN-γ–producing cells and cell-surface markers CD45RA, CD25, CD62L, and CCR7 were assessed by FACS. Numbers in quadrants indicate percentages of the cells in each population. Data are representative of 2 to 4 independent experiments. (B) The data were quantified and presented in a pie chart, in which each slice of the pie represents the fraction of the mean value of a given quadrant.