Evidence that retrograde migration from lung supplies medLN T_RM. (A) 30 d after influenza infection, Thy1.1⁺ P14-bearing mice were treated with 1 µg α-Thy1.1 depleting antibody or IgG2a (control), then analyzed 4 d later for the compartmentalization and phenotype of remaining P14 cells. (B) As in A, except the frequency of P14 cells among total activated CD8⁺ T cells was assessed 4 or 30 d later. Data are graphed as percentage Thy1.1⁺ (P14) of CD44⁺ CD8⁺ T cells. *, P < 0.05 as determined by Student’s t test. (C) CD103 expression among P14 cells isolated from medLN in B, comparing Thy1.1-treated mice (blue) to control IgG2a-treated mice at the indicated time points after antibody treatment. Data are combined from three independent experiments with 8–12 mice per group. **, P < 0.01 as determined by one-way ANOVA. (D and E) Mice were treated with α-Thy1.1 antibody 16 d after influenza infection, and P14 cells were enumerated 2, 4–12, and 30 d later. Data are pooled from two independent experiments. Numbers above bars indicate replicates per group. Endo. (total non-P14 endogenous CD8⁺ T cells) serves as a control Thy1.1^neg population. *, P < 0.05; **, P < 0.01 as determined by an unpaired Student’s t test comparing D2 after depletion to days 4–12 and day 30 after depletion. Similar results were observed in a third independent experiment comparing medLN P14 cell abundance 4 and 30 d after D16 depletion (n ≥ 4, P = 0.038; not depicted). (F) Ki67 staining of P14 cells recovered from the medLN in α-Thy1.1–treated and control mice. Bars represent mean ± SEM.