Figure 2.

Malat1 regulates CD8⁺ T cell memory formation and represses generation of secondary T_EM cells. (A and C) Quantification of splenic NT and Malat1^KD ratios on days 35 and 65 after infection. (B and D) Representative flow cytometry plots of t-T_EM, T_EM, and T_CM cells (left) and quantification (right) among co-transferred cells. (E) P14 CD8⁺ T cells were transduced with Malat1 shRNA (Malat1^KD, CD45.1) or nontarget shRNA (NT, CD45.1.2) and adoptively co-transferred at a 1:1 ratio into CD45.2 recipient mice, which were then infected with LCMV. 35 d after primary infection, Malat1^KD and NT cells were sorted from t-T_EM, T_EM, or T_CM subsets, mixed at a 1:1 (5,000 Malat1^KD cells/5,000 NT cells) ratio, and adoptively transferred into naive CD45.2 recipient followed by infectious challenge with LCMV (secondary infection). (F) Frequency of secondary memory populations derived from transferred t-T_EM (left), T_EM (middle), and T_CM (right) donor cells was assessed at 30 d after secondary LMCV infection. (G) Quantification of secondary memory subsets derived from t-T_EM (left), T_EM (middle), and T_CM (right) donor populations. (H and I) Malat1^KD and NT secondary t-T_EM, T_EM, and T_CM cells were cultured ex vivo in the presence of cognate gp33-41 peptide for 5 h and frequency of IFNγ^hiTNF^hi (H) or IL-2⁺ (I) cells measured. All data are from one representative experiment out of two independent experiments with n = 4–7 (A–D), n = 9–10 (E–G), or n = 4–6 (H and I) mice per group; *, P < 0.05; **, P < 0.005; ***, P < 0.0005, paired t test. Graphs indicate mean ± SEM, symbols represent individual mice. D, day.