PSGL-1 is essential for optimal recruitment of Th1 T cells to the colon during acute colitis. Control WT (uninflamed) and WT DSS-treated (colitis) mice, both expressing WT CD45.2, were adoptively transferred with Th1 CD4+ T cells derived under identical conditions from CD45.1 WT or PSGL-1−/− mice. Mice were euthanized and analyzed 48 hours after adoptive transfer. (A) Cells from spleen and colon LP were stained with anti-CD45.1 mAb–PE, anti–CD45.2 mAb-FITC, as well as anti–CD4 mAb-APC for gating. Numbers on top left quadrant represent the percentages of CD4+ CD45.1+ cells (i.e. adoptively transferred) out of total CD4+ T cells in each compartment. (B) Yields (mean ± SEM) of the transferred CD4+ CD45.1+ cells recovered in spleen and colon LP from each indicated group (n= 3/group) at 48 hours. *, p < 0.01 vs. WT to uninflamed; #, p < 0.01 vs. WT to DSS colitis.