CD4 and CD8 T_Ms differ on their expression of gut-homing markers. (A) Homing marker expression on naive (T_N), effector (T_E), and memory (T_M) CD4 and CD8 T cells analyzed by flow cytometry. CD4 and CD8 T_Ns (gated as CD4⁺CD25⁻CD44^lo and CD8⁺ CD44^lo, respectively) and T_Ms (gated as CD4⁺CD25⁻CD44^hi and CD8⁺CD44^hi, respectively) were naive or memory T cells detected in the spleen of 1-year-old B6 mice. T_Es were generated by stimulating B6 spleen T cells in vitro with anti-CD3 and anti-CD28 for 3 days. Representative histogram plots (top) and measurements of mean fluorescence intensity (MFI; mean ± SEM; bottom) are shown (n = 8). (B,C) Time-course tracking of CD4 and CD8 T cells (gated as Thy1.2⁺CD4⁺ and Thy1.2⁺CD8⁺, respectively) for their tissue homing preference (B) and homing marker expression (C) during their transition from T_Es to T_Ms in Thy1.1 congenic mice receiving adoptive transfer of a mix of equal number (10 × 10⁶) of B6 CD4 and CD8 T_Es. (B) Data are presented as mean ± SEM. (C) Representative homing marker expression on spleen T cells detected by flow cytometry, shown as mean fluorescence intensity (MFI; mean ± SEM). N = 4. Shaded area marks contraction phase.