CX₃CR1 provides a selective advantage to effector CD4⁺ T cells. Equal numbers of LACK-specific CX₃CR1^gfp/gfp and CX₃CR1^+/gfp Th2 or Th1 cells were coinjected into WT mice at day 0. Recipients were sensitized with LACK or PBS at days 1 and 4 and analyzed at day 3 (A, C, and D) or 7 (B and D). (A) Donor cells were analyzed in skin by flow cytometry. Data show representative flow cytometry profiles (top). Data show mean frequencies ± SEM of donor Th1 (bottom left) or Th2 (bottom right) cells among the CD4⁺ T cell population. One representative experiment out of two is shown (n = 6 mice per group). (B) Donor cells were analyzed in skin by flow cytometry (top). Data show donor cell frequency of Th1 (bottom left) or Th2 (bottom right) in individual mice with horizontal bars indicating the mean from three experiments (n = 16 mice per group). *, P < 0.05. (C) 18 h before sacrifice, recipient mice were injected with BrdU, and donor cells were analyzed by flow cytometry after staining with anti-BrdU, anti-Thy1.1, anti-Thy1.2, anti-CD4, and anti-CD45 antibodies. Data show cell frequency of donor Th1 or Th2 cells in individual mice with horizontal bars indicating the mean in LACK-sensitized (n = 4 mice) and PBS-sensitized mice (n = 2–3 mice). One representative experiment out of two is shown. (D) Donor cells were analyzed in draining LNs (dLN) and skin by flow cytometry for GFP expression at days 3 and 7. Data show representative flow cytometry profiles after aggregating files from individual mice (top; n = 6 mice per group). One experiment out of three is shown. Histograms show mean frequencies ± SEM of GFP⁺ cells among Th1 (left) or Th2 (right) donor cells (n = 12 mice per group at day 3 and n = 18 mice at day 7).