Hematopoietic cell–derived interferon influenced CD8 T-cell expansion. Bone marrow chimeras (WT-BM > RIP-GP, irf7^−/−-BM > RIP-GP) were infected with 200 PFU LCMV-WE. (A) Frequencies of LCMV-specific CD8⁺ T cells were analyzed on day 8 in the blood (n = 4-5). (B) Splenic CD8⁺ T cells were analyzed for tet-gp33⁺ cells (LCMV-specific cells) and phenotype. One representative dot plot is shown. Cells are gated on CD8⁺ T cells. (C) Expansion of total CD8⁺ T cells was analyzed in the blood using tetramers (n = 4-5). (D) Expression of IL-7Rα on tet-gp33 positive cells was analyzed in blood-derived CD8⁺ T cells. One of 4 or 5 representative stainings is shown. (E) On day 30, pancreatic islet cells were analyzed for replication of LCMV within the islets. One of 3 representative slides is shown.