Inhibitors of the cell cycle suppress expression of P-lig but not other activation-induced molecules. Naive CD4⁺ T cells were stimulated as in Figure 1 in the absence or presence of the indicated drugs arresting the T cells in different phases of the cell cycle. The percentage of selectin lig-positive cells within CD4⁺ KJ1-26.1⁺ cells was determined on day 3. (A) A representative dot plot of P-lig and E-lig expression among total KJ1-26.1⁺. The percentages of selectin lig-positive cells among all and among undivided (in parentheses) cells is given. (B) Four separate experiments are summarized, and the mean + SD is given. To compare these experiments, the frequency of P-lig–positive cells induced in the absence of cell-cycle inhibitors is set to 100% for each experiment, and the relative frequency within undivided and inhibitor-treated cultures was determined. (C) CD25 expression on KJ1-26.1⁺ cells at day 1 after activation. The mean + SD from 3 separate experiments is given.