Expression of CD62L on CD8+ T cells primed in the presence of IL-12. Spleen and LN suspensions (1 × 106 cells/ml) from OT-1 mice were primed with 1 ug/ml SIINFEKL. Cell suspensions were either: (1) pretreated overnight with 10 ng/ml of IL-12 and then washed and primed with antigen (IL-12→antigen), (2) primed with antigen and IL-12 simultaneously (IL-12 + antigen), (3) primed with antigen overnight and then treated with IL-12 (antigen→IL-12), or (4) primed with antigen alone. Three days after priming cells were re-cultured at a density of 1 × 106 cells/ml. Cells were harvested and expression of CD62L was determined by flow cytometry on Vα2 (antigen specific transgenic cells) on days 4, 5, and 6 after priming (a). Absolute numbers were calculated for each experimental group (b) and were expressed as total cell number