IFNAR blocking at d0–1 of acute LCMV infection directs stem-like T cell differentiation. (A–E) Analysis of P14 cells generated in groups indicated in A. Data are representative of two independent experiments with five mice per group in each experiment. Each dot in C–E represents a single mouse. Data are the mean ± SEM. Statistical differences were analyzed using one-way ANOVA tests. (A) Experimental scheme. P14 cells were transferred into wild-type hosts prior to infection with acute LCMV Armstrong and treated with indicated schedules (d0, d0–1, d2–4, d5–7) of IFNAR blocking monoclonal antibodies. Peripheral lymph node P14 cells were analyzed at d8 of infection. (B) Representative flow cytometry plots of P14 cells showing KLRG1⁺TCF-1⁻ effector T (T_EFF) and KLRG1⁻TCF-1⁺ stem-like T cell populations. (C) Graphs summarizing frequencies in B. (D) Graphs summarizing total P14 cell numbers of T_EFF and stem-like T cell subsets. (E) Graph summarizing total P14 cell number of TCF-1⁺SLAMF6⁺ stem-like T cells as shown in Fig. S1 A. (F and G) IFNAR detection of peripheral lymphocytes following acute LCMV infection and IFNAR blocking as indicated, or control Ifnar^−/− hosts. Data are representative of three independent experiments with four mice per group in each experiment. Average geometric mean fluoresence intensity (gMFI) ± SEM for each group are indicated. (F) Representative histograms of IFNAR expression. (G) Graph summarizing IFNAR gMFI. Statistical differences were analyzed using one-way ANOVA tests. The dashed line indicates anti-IFNAR staining LOD. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. Fig. S1 shows additional supporting data. LOD, limit of detection.