Merozoites, not trophozoites, are the target of Vγ9Vδ2 antiparasitic activity. (A) Primed S1 or JT Vγ9Vδ2 T cells were cocultured with purified trophozoites (E/T ratio 4/1) for either 24 hours until merozoite reinvasion (no removal of γδ) or were removed by magnetic depletion after 6 hours of coculture, just before schizont rupture; [removal of γδ(T6h)]. Mock-treated parasites cultured without cells were used as a control. After cell removal, the parasitemia was similar under the various conditions. (i) Schematic representation of the experimental design. (ii) Antiparasitic activity was calculated as 100 − [(average % parasitemia of duplicate with cells in the presence of IL-2 + IL-15/average % parasitemia of duplicate with cells in the presence of IL-2) × 100]. Data represents the mean ± SD of the antiparasitic activity observed in 3 independent experiments performed in duplicate (*P ≤ .05 for Mann-Whitney rank sum test comparing the conditions [removal of γδ] and [no removal of γδ] for each T-cell line). (iii) Histograms represent the mean of parasitemia ± SD observed in 1 representative experiment performed in duplicate with the S1 and the JT cell lines. No cells: parasites cultured in the absence of cells (*P ≤ .05 by Mann-Whitney rank sum test comparing the parasitemia of parasites cultured in the presence of T cells [S1 or JT] with the parasitemia in absence of T cells [no cells], for each condition (that is, [removal of γδ] or [no removal of γδ]). Flow cytometry histograms show granulysin expression in the S1 and JT cell lines before (T0) and after 6 hours (T6hr) of coculture with trophozoite-stage parasites. Dotted lines represent isotype control antibody. (B) Purified merozoites were incubated with fresh uiRBCs alone (no cells) or in the presence of S1 or JT T cells or the αβ T4A.5 T-cell clone, and the parasitemia was assessed after 28 hours. (i) Schematic representation of the experimental design. (ii) Inhibition of merozoite reinvasion (percentage) was calculated as 100 − [(average % parasitemia with cells/average % parasitemia without cells) × 100]. Data represent the mean ± SD of the inhibition of merozoite invasion observed in 3 independent experiments performed in duplicate (n = 3; *P ≤ .05 by Mann-Whitney rank sum test comparing S1 or JT with T4A.5). (iii) Parasitemia from 1 representative experiment is shown (mean ± SD; *P ≤ .05 by Mann-Whitney rank sum test comparing the parasitemia in the presence of T cells [S1, JT, or T4A.5] with the parasitemia in absence of T cells [no cells]).