FIGURE 2.

CD27 signals are required for the expansion of IFN-γ–producing γδ²⁷⁺ cells. A and B, Total γδ cells were FACS-sorted from pooled spleen and LN of Cd27^+/+.Thy1.1 (WT) and Cd27^−/−.Thy1.2 mice. A, Cells were cocultured at a 50:50 ratio, stimulated with anti-CD3 in the presence of allophycocyanin, and stained for Thy1.2 at indicated time points. B, Cells were coinjected at a 50:50 ratio into TCRd^−/− mice, and after 5 d, splenocytes were harvested and stained for CD3ε, TCRδ, and Thy1.2 to discriminate WT and Cd27^−/− γδ cells. Each dot represents one recipient mouse (n = 4). C, WT and Cd27^−/− mice were infected with MuHV-4 i.p., and cells were harvested from the PEC after 8 d. Percentage of IFN-γ⁺ or IL-17⁺ cells upon intracellular cytokine staining of total γδ cells, FACS-purified from PEC of WT or Cd27^−/− mice. D, WT and Cd27^−/− mice were immunized i.v. with P. berghei ANKA (PbA)-infected RBCs. Absolute numbers of IFN-γ⁺ γδ cells in the spleen at day 4 postinfection. Data in A–D are representative of three independent experiments with similar results. Error bars represent SD (n = 3). *p < 0.05; **p < 0.01; ***p < 0.001.