Figure 1.

4-1BB^−/− mice have elevated early but reduced persistent MCMV-specific CD8 responses. WT C57BL/6 (▪) and 4-1BB-deficient (□) mice were infected with MCMV and on days 0, 7, 14 and 30 post-infection, CD8⁺ cells specific for M45 (A), M57 (B), M38 (C) and m139 (D) were quantified on the basis of intracellular IFN-γ production (E and F). Numbers of peptide-specific CD8⁺ cells 7 (E) and 30 (F) days post-infection. Results are expressed as numbers of peptide-specific CD8⁺ cells/spleen and are shown as mean±SEM of four mice/group, representing three independent experiments. (G) Representative plots of M45-specific tetramer-binding CD44⁺ CD8⁺ T cells from WT (left) and 4-1BB^−/− mice 7 days post-infection. Results represent eight mice from two experiments. (H) Splenic M45-specific CD8⁺ cell numbers 7 days after immunization with M45 peptide/CFA. Mean±SEM of four mice/group is shown. (I) Numbers of peptide specific CD4⁺ cells 7 days post-infection. Individual mice and mean values are shown, and data represent two independent experiments. (J) In vivo CTL assay as described in the Materials and methods section. Representative plots of loaded cells prior to transfer (top) and from MCMV-infected WT (middle) and 4-1BB^−/− (bottom) mice 7 days post-infection are shown, and represent four mice/group. (K) MCMV glycoprotein B content in genomic DNA from spleens of WT and 4-1BB^−/− mice 7 and 30 days post-infection was measured by qPCR and normalized to β-actin. Results are expressed as mean±SEM of three mice/group. (L) Infectious viral load in salivary glands was measured by plaque assay. Individual mice and mean values are shown. (M) Representative plots of M38- and m139-specific tetramer-binding CD8⁺ T cells from WT (left) and 4-1BB^−/− (right) mice 30 days post-infection. Results represent 12 mice from two independent experiments. (N) Numbers of peptide specific CD4⁺ T cells 30 days post-infection. Individual mice are shown and data represent two independent experiments. Significance is ^*p<0.05, Student's t-test.