Frequency of responding cells measured by the IFN-γ Elispot assay and the intracellular IFN-γ content in CD8 T cells.

(A) For Elispot analysis, CBMCs from 17 uninfected (■) and 12 congenitally infected (▪) newborns were stimulated or not with liveT cruzi in the presence or absence of IL-15 (n = 12 and n = 9 in uninfected and infected neonates, respectively). The percentage of positive responses in congenitally infected newborns is indicated above the histograms. *P < .05 vs IL-15 alone (Student test). Visualization of intracellular IFN-γ content in CD8 T cells in one uninfected (B and C) and one congenitally infected newborn (D and E) is also shown. CBMCs were stimulated with IL-15 alone (B and D) or with both IL-15 and liveT cruzi (C and E). Analyses were performed within the CD8 T-cell subset. The percentage of IFN-γ–positive cells is indicated in the upper right quadrant. Two other congenitally infected newborns were tested, resulting in 1 of 2 positive responses.