FIG. 1. HIV Tat enters Jurkat cells but not U937 cells or monocytes. Jurkat cells, U937 cells, and monocytes were exposed to HIV Tat (100ng/ml) for 0 min (lanes 1, 5, and 10), 30 min (lanes 2, 6, and 11), 1 h (lanes 3, 7, and 12), or 3 h (lanes 4, 8, and 1