Memory CD8 T cells in intestinal epithelium do not recirculate. Naive P14 cells were transferred to naive C57BL/6J mice, and recipients were infected with LCMV. 90 d later, 2 µg/ml FTY720 was dissolved in drinking water (white bars) or mice were maintained on normal drinking water (black bars). (A and B) 2 (A) or 30 (B) d after FTY720 treatment, the number of LCMV-specific P14 memory CD8 T cells was determined in blood (PBL), iLNs, lung, or small intestinal epithelium (IEL). Data shown is one of five experiments with three mice per group with similar results. Immune mice were generated by transferring naive Thy1.1⁺ P14 into naive C57BL/6J mice and infecting recipients with LCMV. Error bars indicate SEM. *, P < 0.05; **, P < 0.01; ***, P < 0.001, unpaired Student’s t test. (C) 2 mo later, 7 cm of small intestine, along with associated mesentery and mLN, were transplanted from naive mice into immune mice. (D) 42 d after transplantation, lymphocytes were isolated from host spleen, blood (PBL), mLN, and intestinal epithelium (IEL), as well as donor mLN and IEL. The presence of host memory P14 was determined in each tissue by Thy1.1 staining and flow cytometry. All plots are gated on CD8⁺ lymphocytes and are representative of one of a total of three mice examined in two independent experiments. NA, not applicable.